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S7-1200 Programmable controller

SIMATIC
S7
S7-1200 Programmable controller
System Manual

V4.2, 09/2016
A5E02486680-AK

___________________
Preface
1
___________________
Product overview
2
___________________
New features
STEP 7 programming
3
___________________
software
4
___________________
Installation
___________________
5
PLC concepts
___________________
6
Device configuration
___________________
7
Programming concepts
___________________
8
Basic instructions
___________________
9
Extended instructions
___________________
10
Technology instructions
___________________
11
Communication
___________________
12
Web server
Communication processor
___________________
13
and Modbus TCP
TeleService communication
___________________
14
(SMTP email)
___________________
15
Online and diagnostic tools
___________________
A
Technical specifications
___________________
B
Calculating a power budget
___________________
C
Ordering Information
Device exchange and spare
___________________
D
parts compatibility

Legal information
Warning notice system
This manual contains notices you have to observe in order to ensure your personal safety, as well as to prevent
damage to property. The notices referring to your personal safety are highlighted in the manual by a safety alert
symbol, notices referring only to property damage have no safety alert symbol. These notices shown below are
graded according to the degree of danger.
DANGER
indicates that death or severe personal injury will result if proper precautions are not taken.
WARNING
indicates that death or severe personal injury may result if proper precautions are not taken.
CAUTION
indicates that minor personal injury can result if proper precautions are not taken.
NOTICE
indicates that property damage can result if proper precautions are not taken.
If more than one degree of danger is present, the warning notice representing the highest degree of danger will
be used. A notice warning of injury to persons with a safety alert symbol may also include a warning relating to
property damage.

Qualified Personnel

The product/system described in this documentation may be operated only by personnel qualified for the specific
task in accordance with the relevant documentation, in particular its warning notices and safety instructions.
Qualified personnel are those who, based on their training and experience, are capable of identifying risks and
avoiding potential hazards when working with these products/systems.

Proper use of Siemens products
Note the following:
WARNING
Siemens products may only be used for the applications described in the catalog and in the relevant technical
documentation. If products and components from other manufacturers are used, these must be recommended
or approved by Siemens. Proper transport, storage, installation, assembly, commissioning, operation and
maintenance are required to ensure that the products operate safely and without any problems. The permissible
ambient conditions must be complied with. The information in the relevant documentation must be observed.

Trademarks

All names identified by ® are registered trademarks of Siemens AG. The remaining trademarks in this publication
may be trademarks whose use by third parties for their own purposes could violate the rights of the owner.

Disclaimer of Liability
We have reviewed the contents of this publication to ensure consistency with the hardware and software
described. Since variance cannot be precluded entirely, we cannot guarantee full consistency. However, the
information in this publication is reviewed regularly and any necessary corrections are included in subsequent
editions.

Siemens AG
Division Digital Factory
Postfach 48 48
90026 NÜRNBERG
GERMANY

A5E02486680-AK
Ⓟ 08/2016 Subject to change

Preface
Purpose of the manual
The S7-1200 series is a line of programmable logic controllers (PLCs) that can control a
variety of automation applications. Compact design, low cost, and a powerful instruction set
make the S7-1200 a perfect solution for controlling a wide variety of applications. The S71200 models and the Windows-based STEP 7 programming tool (Page 37) give you the
flexibility you need to solve your automation problems.
This manual provides information about installing and programming the S7-1200 PLCs and
is designed for engineers, programmers, installers, and electricians who have a general
knowledge of programmable logic controllers.

Required basic knowledge
To understand this manual, it is necessary to have a general knowledge of automation and
programmable logic controllers.

Scope of the manual
This manual describes the following products:
● STEP 7 V14 Basic and Professional (Page 37)
● S7-1200 CPU firmware release V4.2
For a complete list of the S7-1200 products described in this manual, refer to the technical
specifications (Page 1359).

Certification, CE label, C-Tick, and other approvals
Refer to the technical specifications (Page 1359) for more information.

Service and support
In addition to our documentation, Siemens offers technical expertise on the Internet and on
the customer support web site (http://support.industry.siemens.com).
Contact your Siemens distributor or sales office for assistance in answering any technical
questions, for training, or for ordering S7 products. Because your sales representatives are
technically trained and have the most specific knowledge about your operations, process
and industry, as well as about the individual Siemens products that you are using, they can
provide the fastest and most efficient answers to any problems you might encounter.

S7-1200 Programmable controller
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Preface

Documentation and information
S7-1200 and STEP 7 provide a variety of documentation and other resources for finding the
technical information that you require.
● The S7-1200 Programmable Controller System Manual provides specific information
about the operation, programming, and the specifications for the complete S7-1200
product family. In addition to the system manual, the S7-1200 Easy Book provides a
more general overview to the capabilities of the S7-1200 family.
Both the system manual and the Easy Book are available as electronic (PDF) manuals.
You can download or view the electronic manuals from the Siemens Industry Online
Support Web site (http://support.industry.siemens.com). The system manual is also
available on the Documents Disk that ships with every S7-1200 CPU.
● The online STEP 7 information system provides immediate access to the conceptual
information and specific instructions that describe the operation and functionality of the
programming package and basic operation of SIMATIC CPUs.
● The Siemens Industry Online Support Web site (http://support.industry.siemens.com)
provides access to the electronic (PDF) versions of the SIMATIC documentation set,
including the system manual, the Easy Book, and the STEP 7 information system.
Existing documents are available from the Product Support link. With this online
documentation access, you can also drag and drop topics from various documents to
create your own custom manual.
You can access online documentation by clicking "mySupport" from the left side of the
page and selecting "Documentation" from the navigation choices. To use the mySupport
Documentation features, you must sign up as a registered user.
● The Update to the S7-1200 System Manual, edition 07/2016
(https://support.industry.siemens.com/cs/ww/en/view/108168658) has updates to the S71200 Programmable Controller System Manual that occurred after publication.
● The Siemens Industry Online Support Web site also provides FAQs and other helpful
documents for S7-1200 and STEP 7.
● You can also follow or join product discussions on the Service & Support technical forum
(https://support.industry.siemens.com/tf/ww/en/?Language=en&siteid=csius&treeLang=e
n&groupid=4000002&extranet=standard&viewreg=WW&nodeid0=34612486). These
forums allow you to interact with various product experts.
– Forum for S7-1200
(https://support.industry.siemens.com/tf/ww/en/threads/237?title=simatic-s71200&skip=0&take=10&orderBy=LastPostDate+desc)
– Forum for STEP 7 Basic
(https://support.industry.siemens.com/tf/ww/en/threads/243?title=step-7-tiaportal&skip=0&take=10&orderBy=LastPostDate+desc)

S7-1200 Programmable controller

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Preface

Security information
Siemens provides products and solutions with industrial security functions that support the
secure operation of plants, systems, machines and networks.
In order to protect plants, systems, machines and networks against cyber threats, it is
necessary to implement – and continuously maintain – a holistic, state-of-the-art industrial
security concept. Siemens’ products and solutions only form one element of such a concept.
Customer is responsible to prevent unauthorized access to its plants, systems, machines
and networks. Systems, machines and components should only be connected to the
enterprise network or the internet if and to the extent necessary and with appropriate security
measures (e.g. use of firewalls and network segmentation) in place.
Additionally, Siemens’ guidance on appropriate security measures should be taken into
account. For more information about industrial security, please visit
(http://www.industry.siemens.com/topics/global/en/industrial-security/Pages/default.aspx).
Siemens’ products and solutions undergo continuous development to make them more
secure. Siemens strongly recommends to apply product updates as soon as available and to
always use the latest product versions. Use of product versions that are no longer supported,
and failure to apply latest updates may increase customer’s exposure to cyber threats.
To stay informed about product updates, subscribe to the Siemens Industrial Security RSS
Feed under (https://support.industry.siemens.com/cs/us/en/).

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Preface

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Table of contents
Preface ................................................................................................................................................... 3
1

Product overview .................................................................................................................................. 27
1.1

Introducing the S7-1200 PLC .................................................................................................27

1.2

Expansion capability of the CPU ............................................................................................30

1.3

Basic HMI panels ....................................................................................................................32

New features......................................................................................................................................... 33

STEP 7 programming software ............................................................................................................. 37

3.1

System requirements ..............................................................................................................38

3.2

Different views to make the work easier .................................................................................39

3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
3.3.8
3.3.9
3.3.10
3.3.11
3.3.12

Easy-to-use tools ....................................................................................................................41
Inserting instructions into your user program .........................................................................41
Accessing instructions from the "Favorites" toolbar ...............................................................41
Creating a complex equation with a simple instruction...........................................................42
Adding inputs or outputs to a LAD or FBD instruction ............................................................44
Expandable instructions ..........................................................................................................44
Selecting a version for an instruction ......................................................................................45
Modifying the appearance and configuration of STEP 7 ........................................................45
Dragging and dropping between editors .................................................................................46
Changing the operating mode of the CPU ..............................................................................47
Changing the call type for a DB ..............................................................................................48
Temporarily disconnecting devices from a network ................................................................49
Virtual unplugging of devices from the configuration ..............................................................50

3.4

Backward compatibility ...........................................................................................................51

Installation ............................................................................................................................................ 53
4.1

Guidelines for installing S7-1200 devices ...............................................................................53

4.2

Power budget ..........................................................................................................................56

4.3
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.6
4.3.7
4.3.8
4.3.8.1
4.3.8.2
4.3.8.3
4.3.8.4

Installation and removal procedures .......................................................................................57
Mounting dimensions for the S7-1200 devices .......................................................................57
Installing and removing the CPU ............................................................................................61
Installing and removing an SB, CB, or BB ..............................................................................63
Installing and removing an SM ...............................................................................................65
Installing and removing a CM or CP .......................................................................................67
Removing and reinstalling the S7-1200 terminal block connector .........................................68
Installing and removing the expansion cable ..........................................................................69
TS (TeleService) adapter ........................................................................................................71
Connecting the TeleService adapter ......................................................................................71
Installing the SIM card ............................................................................................................73
Installing the TS adapter unit on a DIN rail .............................................................................74
Installing the TS adapter on a panel .......................................................................................75

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4.4
5

Wiring guidelines .................................................................................................................... 76

PLC concepts ....................................................................................................................................... 83
5.1
5.1.1
5.1.2
5.1.3
5.1.3.1
5.1.3.2
5.1.3.3
5.1.3.4
5.1.3.5
5.1.3.6
5.1.3.7
5.1.3.8
5.1.3.9
5.1.3.10
5.1.3.11
5.1.3.12
5.1.3.13
5.1.3.14
5.1.3.15
5.1.3.16
5.1.3.17
5.1.4
5.1.5
5.1.5.1
5.1.6
5.1.7
5.1.8

Execution of the user program ............................................................................................... 83
Operating modes of the CPU ................................................................................................. 87
Processing the scan cycle in RUN mode ............................................................................... 91
Organization blocks (OBs) ..................................................................................................... 92
Program cycle OB .................................................................................................................. 92
Startup OB ............................................................................................................................. 93
Time delay interrupt OB ......................................................................................................... 93
Cyclic interrupt OB ................................................................................................................. 94
Hardware interrupt OB ........................................................................................................... 95
Time error interrupt OB .......................................................................................................... 96
Diagnostic error interrupt OB ................................................................................................. 97
Pull or plug of modules OB .................................................................................................. 100
Rack or station failure OB .................................................................................................... 101
Time of day OB .................................................................................................................... 102
Status OB ............................................................................................................................. 102
Update OB ........................................................................................................................... 103
Profile OB ............................................................................................................................. 103
MC-Servo and MC-Interpolator OB...................................................................................... 103
MC-PreServo ....................................................................................................................... 104
MC-PostServo ...................................................................................................................... 105
Event execution priorities and queuing ................................................................................ 105
Monitoring and configuring the cycle time ........................................................................... 109
CPU memory........................................................................................................................ 110
System and clock memory ................................................................................................... 112
Diagnostics buffer ................................................................................................................ 114
Time of day clock ................................................................................................................. 115
Configuring the outputs on a RUN-to-STOP transition ........................................................ 116

5.2
5.2.1

Data storage, memory areas, I/O and addressing ............................................................... 117
Accessing the data of the S7-1200 ...................................................................................... 117

5.3

Processing of analog values ................................................................................................ 123

5.4
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.4.6
5.4.7
5.4.8
5.4.9
5.4.10
5.4.11

Data types ............................................................................................................................ 125
Bool, Byte, Word, and DWord data types ............................................................................ 126
Integer data types ................................................................................................................ 127
Floating-point real data types............................................................................................... 127
Time and Date data types .................................................................................................... 128
Character and String data types .......................................................................................... 130
Array data type ..................................................................................................................... 132
Data structure data type ....................................................................................................... 133
PLC data type ...................................................................................................................... 133
Variant pointer data type ...................................................................................................... 134
Accessing a "slice" of a tagged data type ............................................................................ 134
Accessing a tag with an AT overlay ..................................................................................... 135

5.5
5.5.1
5.5.2

Using a memory card ........................................................................................................... 138
Inserting a memory card in the CPU .................................................................................... 139
Configuring the startup parameter of the CPU before copying the project to the
memory card ........................................................................................................................ 142
Transfer card ........................................................................................................................ 142

5.5.3

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5.5.4
5.5.5

Program card ........................................................................................................................145
Firmware update ...................................................................................................................148

5.6

Recovery from a lost password ............................................................................................151

Device configuration............................................................................................................................ 153
6.1

Inserting a CPU .....................................................................................................................154

6.2

Uploading the configuration of a connected CPU .................................................................156

6.3

Adding modules to the configuration ....................................................................................158

6.4
6.4.1
6.4.2
6.4.3

Configuration control .............................................................................................................159
Advantages and applications of configuration control ..........................................................159
Configuring the central installation and optional modules ....................................................159
Example of configuration control ..........................................................................................166

6.5

Changing a device ................................................................................................................170

6.6
6.6.1
6.6.2
6.6.3

Configuring the operation of the CPU ...................................................................................170
Overview ...............................................................................................................................170
Configuring digital input filter times .......................................................................................172
Pulse catch ...........................................................................................................................174

6.7

Configuring multilingual support ...........................................................................................175

6.8

Configuring the parameters of the modules .........................................................................177

6.9

Configuring the CPU for communication ..............................................................................179

6.10

Time synchronization ............................................................................................................181

Programming concepts ....................................................................................................................... 183
7.1

Guidelines for designing a PLC system ................................................................................183

7.2

Structuring your user program ..............................................................................................185

7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.3.6

Using blocks to structure your program ................................................................................187
Organization block (OB)........................................................................................................188
Function (FC) ........................................................................................................................190
Function block (FB) ...............................................................................................................190
Data block (DB) .....................................................................................................................192
Creating reusable code blocks .............................................................................................194
Passing parameters to blocks...............................................................................................195

7.4

Understanding data consistency ...........................................................................................198

7.5
7.5.1
7.5.2
7.5.3
7.5.3.1
7.5.3.2
7.5.3.3
7.5.4

Programming language.........................................................................................................199
Ladder logic (LAD) ................................................................................................................199
Function Block Diagram (FBD) .............................................................................................200
SCL .......................................................................................................................................201
SCL program editor ...............................................................................................................201
SCL expressions and operations ..........................................................................................202
Indexed addressing with PEEK and POKE instructions .......................................................206
EN and ENO for LAD, FBD and SCL ....................................................................................208

7.6
7.6.1
7.6.2
7.6.3

Protection ..............................................................................................................................210
Access protection for the CPU ..............................................................................................210
External load memory ...........................................................................................................212
Know-how protection ............................................................................................................213

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7.6.4

Copy protection .................................................................................................................... 214

7.7

Downloading the elements of your program ........................................................................ 216

7.8

Synchronizing the online CPU and offline project................................................................ 219

7.9
7.9.1

Uploading from the online CPU ........................................................................................... 221
Comparing the online CPU to the offline CPU ..................................................................... 221

7.10
7.10.1
7.10.2
7.10.3
7.10.4

Debugging and testing the program..................................................................................... 222
Monitor and modify data in the CPU .................................................................................... 222
Watch tables and force tables.............................................................................................. 223
Cross reference to show usage ........................................................................................... 223
Call structure to examine the calling hierarchy .................................................................... 225

Basic instructions .................................................................................................................................227
8.1
8.1.1
8.1.2
8.1.3

Bit logic operations ............................................................................................................... 227
Bit logic instructions ............................................................................................................. 227
Set and reset instructions .................................................................................................... 230
Positive and negative edge instructions .............................................................................. 233

8.2

Timer operations .................................................................................................................. 236

8.3

Counter operations .............................................................................................................. 244

8.4
8.4.1
8.4.2
8.4.3
8.4.4
8.4.4.1
8.4.4.2
8.4.4.3

Comparator operations ........................................................................................................ 250
Compare values instructions................................................................................................ 250
IN_Range (Value within range) and OUT_Range (Value outside range) ............................ 251
OK (Check validity) and NOT_OK (Check invalidity) ........................................................... 252
Variant and array comparison instructions .......................................................................... 253
Equality and non-equality comparison instructions.............................................................. 253
Null comparsion instructions ................................................................................................ 254
IS_ARRAY (Check for ARRAY) ........................................................................................... 254

8.5
8.5.1
8.5.2
8.5.3
8.5.4
8.5.5
8.5.6
8.5.7
8.5.8
8.5.9

Math functions ...................................................................................................................... 255
CALCULATE (Calculate) ..................................................................................................... 255
Add, subtract, multiply and divide instructions ..................................................................... 257
MOD (return remainder of division)...................................................................................... 258
NEG (Create twos complement) .......................................................................................... 259
INC (Increment) and DEC (Decrement) ............................................................................... 259
ABS (Form absolute value) .................................................................................................. 260
MIN (Get minimum) and MAX (Get maximum) .................................................................... 261
LIMIT (Set limit value) .......................................................................................................... 262
Exponent, logarithm, and trigonometry instructions............................................................. 263

8.6
8.6.1

Move operations................................................................................................................... 265
MOVE (Move value), MOVE_BLK (Move block), UMOVE_BLK (Move block
uninterruptible), and MOVE_BLK_VARIANT (Move block) ................................................. 265
Deserialize ........................................................................................................................... 269
Serialize ............................................................................................................................... 272
FILL_BLK (Fill block) and UFILL_BLK (Fill block uninterruptible) ........................................ 275
SWAP (Swap bytes) ............................................................................................................ 276
LOWER_BOUND: (Read out ARRAY low limit) ................................................................... 277
UPPER_BOUND: (Read out ARRAY high limit) .................................................................. 279
Read / Write memory instructions ........................................................................................ 281
PEEK and POKE (SCL only) ............................................................................................... 281
Read and write big and little Endian instructions (SCL)....................................................... 283

8.6.2
8.6.3
8.6.4
8.6.5
8.6.6
8.6.7
8.6.8
8.6.8.1
8.6.8.2

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Table of contents

8.6.9
8.6.9.1
8.6.9.2
8.6.9.3
8.6.10
8.6.10.1

Variant instructions ...............................................................................................................285
VariantGet (Read VARIANT tag value) ................................................................................285
VariantPut (Write VARIANT tag value) .................................................................................286
CountOfElements (Get number of ARRAY elements) ..........................................................287
Legacy instructions ...............................................................................................................288
FieldRead (Read field) and FieldWrite (Write field) instructions ...........................................288

8.7
8.7.1
8.7.2
8.7.3
8.7.4
8.7.5
8.7.6
8.7.6.1
8.7.6.2

Conversion operations ..........................................................................................................290
CONV (Convert value) ..........................................................................................................290
Conversion instructions for SCL ...........................................................................................291
ROUND (Round numerical value) and TRUNC (Truncate numerical value) ........................294
CEIL and FLOOR (Generate next higher and lower integer from floating-point number) ....295
SCALE_X (Scale) and NORM_X (Normalize) ......................................................................296
Variant conversion instructions .............................................................................................299
VARIANT_TO_DB_ANY (Convert VARIANT to DB_ANY) ...................................................299
DB_ANY_TO_VARIANT (Convert DB_ANY to VARIANT) ...................................................300

8.8
8.8.1
8.8.2
8.8.3
8.8.4
8.8.5
8.8.6
8.8.7
8.8.8
8.8.9
8.8.10
8.8.10.1
8.8.10.2
8.8.10.3
8.8.10.4
8.8.10.5
8.8.10.6
8.8.10.7
8.8.10.8
8.8.10.9
8.8.10.10

Program control operations ..................................................................................................302
JMP (Jump if RLO = 1), JMPN (Jump if RLO = 0), and Label (Jump label) instructions .....302
JMP_LIST (Define jump list) .................................................................................................303
SWITCH (Jump distributor) ...................................................................................................304
RET (Return) .........................................................................................................................306
ENDIS_PW (Enable/disable CPU passwords) .....................................................................307
RE_TRIGR (Restart cycle monitoring time) ..........................................................................309
STP (Exit program) ...............................................................................................................310
GET_ERROR and GET_ERROR_ID (Get error and error ID locally) instructions ...............311
RUNTIME (Measure program runtime) .................................................................................314
SCL program control statements ..........................................................................................316
Overview of SCL program control statements ......................................................................316
IF-THEN statement ...............................................................................................................317
CASE statement ...................................................................................................................318
FOR statement ......................................................................................................................320
WHILE-DO statement ...........................................................................................................321
REPEAT-UNTIL statement ...................................................................................................322
CONTINUE statement ..........................................................................................................323
EXIT statement .....................................................................................................................324
GOTO statement ...................................................................................................................325
RETURN statement ..............................................................................................................325

8.9
8.9.1
8.9.2
8.9.3
8.9.4

Word logic operations ...........................................................................................................326
AND, OR, and XOR logic operation instructions ..................................................................326
INV (Create ones complement) ............................................................................................327
DECO (Decode) and ENCO (Encode) instructions ..............................................................327
SEL (Select), MUX (Multiplex), and DEMUX (Demultiplex) instructions ..............................329

8.10
8.10.1
8.10.2

Shift and rotate ......................................................................................................................332
SHR (Shift right) and SHL (Shift left) instructions .................................................................332
ROR (Rotate right) and ROL (Rotate left) instructions .........................................................333

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Extended instructions ...........................................................................................................................335
9.1
9.1.1
9.1.2
9.1.3
9.1.4
9.1.5

Date, time-of-day, and clock functions ................................................................................. 335
Date and time-of-day instructions ........................................................................................ 335
Clock functions ..................................................................................................................... 338
TimeTransformationRule data structure .............................................................................. 342
SET_TIMEZONE (Set timezone) ......................................................................................... 343
RTM (Runtime meters) ........................................................................................................ 344

9.2
9.2.1
9.2.2
9.2.3
9.2.3.1

9.2.3.3
9.2.4
9.2.4.1
9.2.4.2
9.2.4.3
9.2.4.4
9.2.4.5
9.2.4.6
9.2.4.7
9.2.4.8
9.2.5
9.2.5.1
9.2.5.2
9.2.5.3
9.2.5.4
9.2.5.5

String and character ............................................................................................................. 346
String data overview ............................................................................................................ 346
S_MOVE (Move character string) ........................................................................................ 346
String conversion instructions .............................................................................................. 347
S_CONV, STRG_VAL, and VAL_STRG (Convert to/from character string and number)
instructions ........................................................................................................................... 347
Strg_TO_Chars and Chars_TO_Strg (Convert to/from character string and array of
CHAR) instructions .............................................................................................................. 357
ATH and HTA (Convert to/from ASCII string and hexadecimal number) instructions ......... 359
String operation instructions ................................................................................................ 361
MAX_LEN (Maximum length of a character string).............................................................. 361
LEN (Determine the length of a character string) ................................................................ 362
CONCAT (Combine character strings) ................................................................................ 363
LEFT, RIGHT, and MID (Read substrings in a character string) instructions ...................... 364
DELETE (Delete characters in a character string)............................................................... 365
INSERT (Insert characters in a character string) ................................................................. 366
REPLACE (Replace characters in a character string) ......................................................... 367
FIND (Find characters in a character string) ........................................................................ 369
Runtime information ............................................................................................................. 370
GetSymbolName (Read out a tag on the input parameter) ................................................. 370
GetSymbolPath (Query composite global name of the input parameter assignment) ........ 373
GetInstanceName (Read out name of the block instance) .................................................. 376
GetInstancePath (Query composite global name of the block instance) ............................. 379
GetBlockName (Read out name of the block) ..................................................................... 381

9.3
9.3.1
9.3.2
9.3.3
9.3.4
9.3.5
9.3.6
9.3.7
9.3.8
9.3.9
9.3.10
9.3.10.1
9.3.10.2
9.3.10.3
9.3.10.4

Distributed I/O (PROFINET, PROFIBUS, or AS-i) ............................................................... 384
Distributed I/O Instructions ................................................................................................... 384
RDREC and WRREC (Read/write data record) ................................................................... 385
GETIO (Read process image) ............................................................................................. 388
SETIO (Transfer process image) ......................................................................................... 389
GETIO_PART (Read process image area) .......................................................................... 390
SETIO_PART (Transfer process image area) ..................................................................... 392
RALRM (Receive interrupt) .................................................................................................. 394
D_ACT_DP (Enable/disable PROFINET IO devices) .......................................................... 398
STATUS parameter for RDREC, WRREC, and RALRM ..................................................... 403
Others .................................................................................................................................. 408
DPRD_DAT and DPWR_DAT (Read/write consistent data) ................................................ 408
RCVREC (I-device/I-slave receive data record) .................................................................. 411
PRVREC (I-device/I-slave make data record available) ...................................................... 413
DPNRM_DG (Read diagnostic data from a PROFIBUS DP slave) ..................................... 416

9.4

PROFIenergy ....................................................................................................................... 419

9.5
9.5.1
9.5.2

Interrupts .............................................................................................................................. 420
ATTACH and DETACH (Attach/detach an OB and an interrupt event) instructions ........... 420
Cyclic interrupts.................................................................................................................... 424

9.2.3.2

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

9.5.2.1
9.5.2.2
9.5.3
9.5.3.1
9.5.3.2
9.5.3.3
9.5.3.4
9.5.4
9.5.5

SET_CINT (Set cyclic interrupt parameters).........................................................................424
QRY_CINT (Query cyclic interrupt parameters) ...................................................................426
Time of day interrupts ...........................................................................................................427
SET_TINTL (Set time of day interrupt) .................................................................................428
CAN_TINT (Cancel time of day interrupt) .............................................................................429
ACT_TINT (Activate time of day interrupt) ............................................................................430
QRY_TINT (Query status of time of day interrupt) ...............................................................431
Time delay interrupts ............................................................................................................432
DIS_AIRT and EN_AIRT (Delay/enable execution of higher priority interrupts and
asynchronous error events) instructions ...............................................................................435

9.6
9.6.1

Alarms ...................................................................................................................................436
Gen_UsrMsg (Generate user diagnostic alarms) .................................................................436

9.7
9.7.1
9.7.2
9.7.3
9.7.4
9.7.5
9.7.6
9.7.7
9.7.7.1
9.7.8
9.7.8.1
9.7.9
9.7.10

Diagnostics (PROFINET or PROFIBUS) ..............................................................................439
Diagnostic instructions ..........................................................................................................439
RD_SINFO (Read current OB start information) ..................................................................440
LED (Read LED status) ........................................................................................................450
Get_IM_Data (Read the identification and maintenance data) .............................................451
Get_Name (Read the name of a PROFINET IO device) ......................................................453
GetStationInfo (Read the IP or MAC address of a PROFINET IO device)...........................460
DeviceStates instruction .......................................................................................................468
DeviceStates example configurations...................................................................................469
ModuleStates instruction ......................................................................................................474
ModuleStates example configurations ..................................................................................476
GET_DIAG (Read diagnostic information) ............................................................................480
Diagnostic events for distributed I/O .....................................................................................486

9.8
9.8.1
9.8.2
9.8.3
9.8.4

Pulse .....................................................................................................................................487
CTRL_PWM (Pulse width modulation) .................................................................................487
CTRL_PTO (Pulse train output) ............................................................................................488
Operation of the pulse outputs ..............................................................................................492
Configuring a pulse channel for PWM or PTO .....................................................................494

9.9
9.9.1
9.9.1.1
9.9.1.2
9.9.1.3
9.9.1.4
9.9.2
9.9.2.1
9.9.2.2
9.9.2.3
9.9.2.4
9.9.2.5

Recipes and Data logs ..........................................................................................................498
Recipes .................................................................................................................................498
Recipe overview ....................................................................................................................498
Recipe example ....................................................................................................................499
Program instructions that transfer recipe data ......................................................................502
Recipe example program ......................................................................................................506
Data logs ...............................................................................................................................509
Data log record structure ......................................................................................................509
Program instructions that control data logs ..........................................................................510
Working with data logs ..........................................................................................................525
Limit to the size of data log files ............................................................................................526
Data log example program ...................................................................................................529

9.10
9.10.1
9.10.2
9.10.3
9.10.4

Data block control .................................................................................................................534
CREATE_DB (Create data block) .........................................................................................534
READ_DBL and WRIT_DBL (Read/write a data block in load memory) instructions ...........538
ATTR_DB (Read data block attribute) ..................................................................................541
DELETE_DB (Delete data block) ..........................................................................................542

9.11
9.11.1

Address handling ..................................................................................................................544
GEO2LOG (Determine the hardware identifier from the slot)...............................................544

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

9.11.2
9.11.3
9.11.4
9.11.5

LOG2GEO (Determine the slot from the hardware identifier) .............................................. 546
IO2MOD (Determine the hardware identifier from an I/O address) ..................................... 548
RD_ADDR (Determine the IO addresses from the hardware identifier) .............................. 550
GEOADDR system data type............................................................................................... 551

9.12

Common error codes for the Extended instructions ............................................................ 553

Technology instructions .......................................................................................................................555
10.1
10.1.1
10.1.1.1
10.1.1.2
10.1.1.3
10.1.2
10.1.2.1
10.1.2.2
10.1.2.3
10.1.2.4
10.1.2.5
10.1.3
10.1.3.1
10.1.3.2
10.1.3.3
10.1.3.4
10.1.3.5
10.1.3.6
10.1.3.7
10.1.3.8
10.1.3.9
10.1.3.10
10.1.4
10.1.4.1
10.1.4.2
10.1.4.3

Counting (High-speed counters) .......................................................................................... 555
CTRL_HSC_EXT (Control high-speed counter) instruction ................................................. 556
Instruction overview ............................................................................................................. 556
Example ............................................................................................................................... 557
CTRL_HSC_EXT Instruction System Data Types (SDT)..................................................... 561
Operating the high-speed counter ....................................................................................... 566
Synchronization function ...................................................................................................... 566
Gate function ........................................................................................................................ 567
Capture function ................................................................................................................... 569
Compare function ................................................................................................................. 570
Applications .......................................................................................................................... 571
Configuring a high-speed counter ........................................................................................ 572
Type of Counting .................................................................................................................. 573
Operating phase................................................................................................................... 574
Initial values ......................................................................................................................... 578
Input functions ...................................................................................................................... 578
Output function ..................................................................................................................... 579
Interrupt events .................................................................................................................... 580
Hardware input pin assignment ........................................................................................... 580
Hardware output pin assignment ......................................................................................... 582
HSC input memory addresses ............................................................................................. 583
Hardware identifier ............................................................................................................... 583
Legacy CTRL_HSC (Control high-speed counter) instruction ............................................. 584
Instruction overview ............................................................................................................. 584
Using CTRL_HSC ................................................................................................................ 586
HSC current count value ...................................................................................................... 587

10.2
10.2.1
10.2.2
10.2.2.1
10.2.2.2
10.2.2.3
10.2.2.4
10.2.3
10.2.3.1
10.2.3.2
10.2.3.3
10.2.4
10.2.4.1
10.2.4.2
10.2.4.3
10.2.5
10.2.6
10.2.7

PID control ........................................................................................................................... 588
Inserting the PID instruction and technology object............................................................. 590
PID_Compact ....................................................................................................................... 592
PID_Compact instruction ..................................................................................................... 592
PID_Compact instruction Process value limits .................................................................... 596
PID_Compact instruction ErrorBit parameters ..................................................................... 597
PID_Compact instruction Warning parameters .................................................................... 599
PID_3Step ............................................................................................................................ 600
PID_3Step instruction .......................................................................................................... 600
PID_3Step instruction ErrorBit parameters .......................................................................... 607
PID_3Step instruction Warning parameters ......................................................................... 609
PID_Temp ............................................................................................................................ 610
PID_Temp instruction ........................................................................................................... 610
PID_Temp ErrorBit parameters............................................................................................ 619
PID_Temp Warning parameters .......................................................................................... 621
Configuring the PID_Compact and PID_3Step controllers .................................................. 622
Configuring the PID_Temp controller ................................................................................... 625
Commissioning the PID_Compact and PID_3Step controllers ............................................ 640

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

10.2.8

Commissioning the PID_Temp controller .............................................................................642

10.3
10.3.1
10.3.2
10.3.3
10.3.3.1
10.3.3.2
10.3.4
10.3.4.1
10.3.4.2
10.3.4.3
10.3.4.4
10.3.4.5
10.3.4.6
10.3.4.7
10.3.5
10.3.6
10.3.6.1
10.3.6.2
10.3.6.3
10.3.6.4
10.3.7
10.3.7.1
10.3.7.2
10.3.7.3
10.3.7.4
10.3.7.5
10.3.7.6
10.3.7.7
10.3.7.8
10.3.7.9
10.3.7.10
10.3.7.11
10.3.7.12
10.3.7.13
10.3.8
10.3.8.1
10.3.8.2
10.3.8.3
10.3.9

Motion control .......................................................................................................................653
Phasing .................................................................................................................................658
Configuring a pulse generator ..............................................................................................661
Open loop motion control ......................................................................................................662
Configuring the axis ..............................................................................................................662
Commissioning .....................................................................................................................666
Closed loop motion control ...................................................................................................672
Configuring the axis ..............................................................................................................672
ServoOBs ..............................................................................................................................679
Speed controlled operation ...................................................................................................681
Telegram 4 support ...............................................................................................................684
Simulation axis ......................................................................................................................689
Data adaptation .....................................................................................................................691
Axis control using the TM Pulse module...............................................................................702
Configuring the TO_CommandTable_PTO ...........................................................................708
Operation of motion control for S7-1200...............................................................................711
CPU outputs used for motion control ....................................................................................711
Hardware and software limit switches for motion control .....................................................713
Homing ..................................................................................................................................723
Jerk limit ................................................................................................................................730
Motion control instructions ....................................................................................................731
MC instruction overview ........................................................................................................731
MC_Power (Release/block axis) ...........................................................................................733
MC_Reset (Confirm error).....................................................................................................736
MC_Home (Home axis).........................................................................................................737
MC_Halt (Pause axis) ...........................................................................................................740
MC_MoveAbsolute (Position axis absolutely) .......................................................................742
MC_MoveRelative (Position axis relatively) ..........................................................................745
MC_MoveVelocity (Move axis at predefined velocity) ..........................................................747
MC_MoveJog (Move axis in jog mode) .................................................................................749
MC_CommandTable (Run axis commans as movement sequence) ...................................751
MC_ChangeDynamic (Change dynamc settings for the axis) ..............................................754
MC_WriteParam (write parameters of a technology object) .................................................756
MC_ReadParam instruction (read parameters of a technology object) ................................758
Monitoring active commands ................................................................................................760
Monitoring MC instructions with a "Done" output parameter ................................................760
Monitoring the MC_Velocity ..................................................................................................764
Monitoring the MC_MoveJog ................................................................................................768
ErrorIDs and ErrorInfos for motion control ............................................................................772

Communication ................................................................................................................................... 799
11.1

Asynchronous communication connections .........................................................................801

11.2
11.2.1
11.2.2
11.2.3
11.2.3.1
11.2.3.2
11.2.3.3
11.2.3.4

PROFINET ............................................................................................................................804
Creating a network connection .............................................................................................806
Configuring the Local/Partner connection path ....................................................................807
Assigning Internet Protocol (IP) addresses ..........................................................................810
Assigning IP addresses to programming and network devices ............................................810
Checking the IP address of your programming device .........................................................812
Assigning an IP address to a CPU online .............................................................................813
Configuring an IP address for a CPU in your project ............................................................814

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

11.2.4
11.2.5
11.2.6
11.2.7
11.2.8
11.2.8.1
11.2.8.2
11.2.8.3
11.2.8.4
11.2.8.5
11.2.8.6
11.2.8.7
11.2.8.8
11.2.8.9
11.2.8.10
11.2.8.11
11.2.8.12
11.2.8.13
11.2.8.14
11.2.8.15
11.2.8.16
11.2.8.17
11.2.9
11.2.9.1
11.2.9.2
11.2.9.3
11.2.9.4
11.2.10
11.2.10.1
11.2.11
11.2.11.1
11.2.11.2
11.2.11.3
11.2.12
11.2.12.1
11.2.12.2
11.2.12.3
11.2.12.4
11.2.13
11.2.13.1
11.2.13.2
11.2.13.3
11.2.13.4
11.2.13.5
11.2.14
11.2.14.1
11.2.14.2
11.2.14.3
11.2.15
11.2.15.1
11.2.15.2
11.2.15.3

Testing the PROFINET network .......................................................................................... 819
Locating the Ethernet (MAC) address on the CPU .............................................................. 820
Configuring Network Time Protocol (NTP) synchronization ................................................ 822
PROFINET device start-up time, naming, and address assignment ................................... 824
Open user communication ................................................................................................... 825
Protocols .............................................................................................................................. 825
TCP and ISO on TCP .......................................................................................................... 826
Communication services and used port numbers ................................................................ 827
Ad hoc mode ........................................................................................................................ 828
Connection IDs for the Open user communication instructions ........................................... 828
Parameters for the PROFINET connection ......................................................................... 832
TSEND_C and TRCV_C instructions ................................................................................... 836
Legacy TSEND_C and TRCV_C instructions ...................................................................... 848
TCON, TDISCON, TSEND, and TRCV instructions ............................................................ 856
Legacy TCON, TDISCON, TSEND, and TRCV instructions ............................................... 867
T_RESET (Terminate and re-establish an existing connection) instruction ........................ 878
T_DIAG (Checks the status of connection and reads information) instruction .................... 880
TMAIL_C (Send an email using the Ethernet interface of the CPU) instruction .................. 885
UDP ...................................................................................................................................... 894
TUSEND and TURCV .......................................................................................................... 895
T_CONFIG ........................................................................................................................... 901
Common parameters for instructions ................................................................................... 912
Communication with a programming device ........................................................................ 913
Establishing the hardware communications connection ...................................................... 914
Configuring the devices ....................................................................................................... 914
Assigning Internet Protocol (IP) addresses ......................................................................... 915
Testing your PROFINET network ........................................................................................ 915
HMI-to-PLC communication ................................................................................................. 916
Configuring logical network connections between two devices ........................................... 917
PLC-to-PLC communication ................................................................................................ 918
Configuring logical network connections between two devices ........................................... 919
Configuring the Local/Partner connection path between two devices ................................. 919
Configuring transmit (send) and receive parameters........................................................... 919
Configuring a CPU and PROFINET IO device .................................................................... 922
Adding a PROFINET IO device ........................................................................................... 922
Assigning CPUs and device names ..................................................................................... 923
Assigning Internet Protocol (IP) addresses ......................................................................... 924
Configuring the IO cycle time ............................................................................................... 924
Configuring a CPU and PROFINET I-device ....................................................................... 926
I-device functionality ............................................................................................................ 926
Properties and advantages of the I-device .......................................................................... 927
Characteristics of an I-device............................................................................................... 928
Data exchange between higher- and lower-level IO system ............................................... 931
Configuring the I-device ....................................................................................................... 933
Shared devices .................................................................................................................... 936
Shared device functionality .................................................................................................. 936
Example: Configuring a shared device (GSD configuration) ............................................... 939
Example: Configuring an I-device as a shared device ........................................................ 945
Media Redundancy Protocol (MRP) .................................................................................... 954
Media redundancy with ring topologies ............................................................................... 954
Using Media Redundancy Protocol (MRP) .......................................................................... 956
Configuring media redundancy ............................................................................................ 959

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

11.2.16
11.2.16.1
11.2.16.2
11.2.17
11.2.17.1
11.2.18
11.2.19
11.2.20
11.2.21

S7 routing ..............................................................................................................................962
S7 routing between CPU and CP interfaces ........................................................................963
S7 routing between two CP interfaces..................................................................................963
Disabling SNMP ....................................................................................................................964
Disabling SNMP ....................................................................................................................965
Diagnostics ...........................................................................................................................967
Distributed I/O instructions ....................................................................................................967
Diagnostic instructions ..........................................................................................................967
Diagnostic events for distributed I/O .....................................................................................967

11.3
11.3.1
11.3.2
11.3.3
11.3.3.1
11.3.3.2
11.3.3.3
11.3.4
11.3.5
11.3.6

PROFIBUS ............................................................................................................................968
Communications services of the PROFIBUS CMs ...............................................................970
Reference to the PROFIBUS CM user manuals ..................................................................971
Configuring a DP master and slave device...........................................................................971
Adding the CM 1243-5 (DP master) module and a DP slave ...............................................971
Configuring logical network connections between two PROFIBUS devices ........................972
Assigning PROFIBUS addresses to the CM 1243-5 module and DP slave .........................972
Distributed I/O instructions ....................................................................................................974
Diagnostic instructions ..........................................................................................................974
Diagnostic events for distributed ...........................................................................................974

11.4
11.4.1
11.4.1.1
11.4.1.2
11.4.1.3
11.4.1.4
11.4.2
11.4.2.1
11.4.2.2
11.4.3
11.4.4

AS-i .......................................................................................................................................975
Configuring an AS-i master and slave device .......................................................................976
Adding the AS-i master CM 1243-2 and AS-i slave ..............................................................976
Configuring logical network connections between two AS-i devices ....................................977
Configuring the properties of the AS-i master CM1243-2.....................................................977
Assigning an AS-i address to an AS-i slave .........................................................................978
Exchanging data between the user program and AS-i slaves ..............................................981
STEP 7 basic configuration ..................................................................................................981
Configuring slaves with STEP 7 ...........................................................................................982
Distributed I/O instructions ....................................................................................................984
Working with AS-i online tools ..............................................................................................984

11.5
11.5.1
11.5.2
11.5.3
11.5.4
11.5.4.1
11.5.4.2

S7 communication ................................................................................................................986
GET and PUT (Read and write from a remote CPU) ...........................................................986
Creating an S7 connection ...................................................................................................991
Configuring the Local/Partner connection path between two devices ..................................992
GET/PUT connection parameter assignment .......................................................................992
Connection parameters.........................................................................................................993
Configuring a CPU-to-CPU S7 connection ...........................................................................995

Web server ........................................................................................................................................1001
12.1

Enabling the Web server ....................................................................................................1003

12.2

Configuring Web server users ............................................................................................1005

12.3

Accessing the Web pages from a PC .................................................................................1007

12.4

Accessing the Web pages from a mobile device ................................................................1009

12.5

Using a CP module to access Web pages .........................................................................1010

12.6
12.6.1
12.6.2
12.6.3

Standard Web pages ..........................................................................................................1011
Layout of the standard Web pages .....................................................................................1011
Basic pages ........................................................................................................................1012
Logging in and user privileges ............................................................................................1013

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

12.6.4
12.6.5
12.6.6
12.6.7
12.6.8
12.6.9
12.6.10
12.6.11
12.6.12
12.6.13

Introduction ........................................................................................................................ 1017
Start .................................................................................................................................... 1018
Diagnostics ......................................................................................................................... 1019
Diagnostic Buffer ................................................................................................................ 1022
Module Information ............................................................................................................ 1023
Communication .................................................................................................................. 1027
Tag status .......................................................................................................................... 1031
Watch tables ...................................................................................................................... 1033
Online backup .................................................................................................................... 1035
File Browser ....................................................................................................................... 1037

12.7
12.7.1
12.7.2
12.7.2.1
12.7.2.2
12.7.2.3
12.7.2.4
12.7.2.5
12.7.2.6
12.7.2.7
12.7.2.8
12.7.2.9
12.7.2.10
12.7.2.11
12.7.3
12.7.4
12.7.5
12.7.6
12.7.7
12.7.8
12.7.9
12.7.9.1
12.7.9.2
12.7.9.3
12.7.9.4
12.7.9.5
12.7.9.6
12.7.9.7
12.7.10
12.7.10.1
12.7.10.2
12.7.10.3
12.7.11

User-defined Web pages ................................................................................................... 1040
Creating HTML pages ........................................................................................................ 1041
AWP commands supported by the S7-1200 Web server .................................................. 1042
Reading variables .............................................................................................................. 1044
Writing variables................................................................................................................. 1045
Reading special variables .................................................................................................. 1047
Writing special variables .................................................................................................... 1048
Using an alias for a variable reference .............................................................................. 1049
Defining enum types .......................................................................................................... 1050
Referencing CPU variables with an enum type ................................................................. 1051
Creating fragments ............................................................................................................ 1052
Importing fragments ........................................................................................................... 1053
Combining definitions ......................................................................................................... 1054
Handling tag names that contain special characters ......................................................... 1055
Configuring use of user-defined Web pages ..................................................................... 1057
Configuring the entry page ................................................................................................. 1058
Programming the WWW instruction for user-defined web pages ...................................... 1059
Downloading the program blocks to the CPU .................................................................... 1060
Accessing the user-defined Web pages ............................................................................ 1061
Constraints specific to user-defined Web pages ............................................................... 1062
Example of a user-defined web page ................................................................................ 1063
Web page for monitoring and controlling a wind turbine.................................................... 1063
Reading and displaying controller data .............................................................................. 1065
Using an enum type ........................................................................................................... 1066
Writing user input to the controller ..................................................................................... 1067
Writing a special variable ................................................................................................... 1068
Reference: HTML listing of remote wind turbine monitor Web page ................................. 1068
Configuration in STEP 7 of the example Web page .......................................................... 1073
Setting up user-defined Web pages in multiple languages ............................................... 1074
Creating the folder structure .............................................................................................. 1074
Programming the language switch..................................................................................... 1075
Configuring STEP 7 to use a multi-language page structure ............................................ 1078
Advanced user-defined Web page control ......................................................................... 1078

12.8
12.8.1
12.8.2
12.8.3
12.8.4
12.8.5

Constraints ......................................................................................................................... 1082
Use of JavaScript ............................................................................................................... 1083
Feature restrictions when the Internet options do not allow cookies ................................. 1083
Rules for entering tag names and values .......................................................................... 1084
Importing the Siemens security certificate ......................................................................... 1085
Importing CSV format data logs to non-USA/UK versions of Microsoft Excel ................... 1086

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

Communication processor and Modbus TCP ......................................................................................1087
13.1

Using the serial communication interfaces .........................................................................1087

13.2

Biasing and terminating an RS485 network connector .......................................................1088

13.3
13.3.1
13.3.2
13.3.3
13.3.3.1
13.3.3.2
13.3.3.3
13.3.4
13.3.4.1
13.3.4.2
13.3.5
13.3.5.1
13.3.5.2
13.3.5.3
13.3.5.4
13.3.5.5
13.3.5.6
13.3.5.7
13.3.5.8
13.3.5.9
13.3.5.10
13.3.5.11
13.3.5.12
13.3.6
13.3.6.1
13.3.7
13.3.7.1
13.3.7.2
13.3.7.3
13.3.7.4
13.3.7.5

Point-to-point (PtP) communication ....................................................................................1090
PtP, Freeport communication .............................................................................................1090
3964(R) communication ......................................................................................................1092
Configuring the PtP Freeport communication .....................................................................1093
Managing flow control .........................................................................................................1095
Configuring transmit (send) parameters .............................................................................1096
Configuring receive parameters ..........................................................................................1097
Configuring 3964(R) communication ..................................................................................1105
Configuring the 3964(R) communication ports ...................................................................1105
Configuring the 3964(R) priority and protocol parameters .................................................1106
Point-to-point instructions ...................................................................................................1108
Common parameters for Point-to-Point instructions ...........................................................1108
Port_Config (Configure communication parameters dynamically) .....................................1110
Send_Config (Configure serial transmission parameters dynamically) ..............................1112
Receive_Config (Configure serial receive parameters dynamically) ..................................1115
P3964_Config (Configuring the 3964(R) protocol) .............................................................1120
Send_P2P (Transmit send buffer data) ..............................................................................1122
Receive_P2P (Enable receive messages)..........................................................................1126
Receive_Reset (Delete receive buffer) ...............................................................................1128
Signal_Get (Query RS-232 signals)....................................................................................1129
Signal_Set (Set RS-232 signals) ........................................................................................1130
Get_Features ......................................................................................................................1131
Set_Features .......................................................................................................................1132
Programming the PtP communications ..............................................................................1134
Polling architecture .............................................................................................................1135
Example: Point-to-Point communication .............................................................................1136
Configuring the communication module .............................................................................1137
RS422 and RS485 operating modes ..................................................................................1140
Programming the STEP 7 program ....................................................................................1143
Configuring the terminal emulator .......................................................................................1145
Running the example program ...........................................................................................1145

13.4
13.4.1
13.4.2
13.4.3
13.4.3.1
13.4.3.2
13.4.3.3
13.4.3.4
13.4.4
13.4.5
13.4.6

Universal serial interface (USS) communication ................................................................1146
Selecting the version of the USS instructions .....................................................................1149
Requirements for using the USS protocol ..........................................................................1150
USS instructions .................................................................................................................1153
USS_Port_Scan (Edit communication using USS network) ...............................................1153
USS_Drive_Control (Swap data with drive) ........................................................................1154
USS_Read_Param (Readout parameters from the drive) ..................................................1157
USS_Write_Param (Change parameters in the drive) ........................................................1158
USS status codes ...............................................................................................................1160
USS general drive setup requirements ...............................................................................1162
Example: USS general drive connection and setup ...........................................................1162

13.5
13.5.1
13.5.2
13.5.2.1
13.5.2.2

Modbus communication ......................................................................................................1166
Overview of Modbus RTU and Modbus TCP communication ............................................1166
Modbus TCP .......................................................................................................................1169
Overview .............................................................................................................................1169
Selecting the version of the Modbus TCP instructions .......................................................1170

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

13.5.2.3
13.5.2.4
13.5.3
13.5.3.1
13.5.3.2
13.5.3.3
13.5.3.4
13.5.3.5

Modbus TCP instructions ................................................................................................... 1171
Modbus TCP examples ...................................................................................................... 1185
Modbus RTU ...................................................................................................................... 1191
Overview ............................................................................................................................ 1191
Selecting the version of the Modbus RTU instructions ...................................................... 1193
Maximum number of supported Modbus slaves ................................................................ 1193
Modbus RTU instructions ................................................................................................... 1194
Modbus RTU examples ..................................................................................................... 1213

13.6
13.6.1
13.6.1.1
13.6.1.2
13.6.1.3
13.6.1.4
13.6.1.5
13.6.1.6
13.6.1.7
13.6.1.8

Legacy PtP communication (CM/CB 1241 only) ................................................................ 1217
Legacy point-to-point instructions ...................................................................................... 1218
PORT_CFG (Configure communication parameters dynamically) .................................... 1218
SEND_CFG (Configure serial transmission parameters dynamically) .............................. 1220
RCV_CFG (Configure serial receive parameters dynamically) ......................................... 1221
SEND_PTP (Transmit send buffer data) ............................................................................ 1226
RCV_PTP (Enable receive messages) .............................................................................. 1229
RCV_RST (Delete receive buffer) ...................................................................................... 1231
SGN_GET (Query RS-232 signals) ................................................................................... 1232
SGN_SET (Set RS-232 signals) ........................................................................................ 1233

13.7
13.7.1
13.7.2
13.7.3
13.7.3.1
13.7.3.2
13.7.3.3
13.7.3.4
13.7.4
13.7.5

Legacy USS communication (CM/CB 1241 only) .............................................................. 1234
Selecting the version of the USS instructions .................................................................... 1235
Requirements for using the USS protocol ......................................................................... 1236
Legacy USS instructions .................................................................................................... 1239
USS_PORT (Edit communication using USS network) instruction .................................... 1239
USS_DRV (Swap data with drive) instruction .................................................................... 1240
USS_RPM (Readout parameters from the drive) instruction ............................................. 1243
USS_WPM (Change parameters in the drive) instruction.................................................. 1244
Legacy USS status codes .................................................................................................. 1246
Legacy USS general drive setup requirements ................................................................. 1248

13.8
13.8.1
13.8.2
13.8.3
13.8.3.1
13.8.3.2
13.8.4
13.8.4.1
13.8.4.2
13.8.4.3
13.8.4.4
13.8.4.5

Legacy Modbus TCP communication ................................................................................ 1249
Overview ............................................................................................................................ 1249
Selecting the version of the Modbus TCP instructions ...................................................... 1249
Legacy Modbus TCP instructions ...................................................................................... 1250
MB_CLIENT (Communicate using PROFINET as Modbus TCP client) ............................ 1250
MB_SERVER (Communicate using PROFINET as Modbus TCP server) ........................ 1257
Legacy Modbus TCP examples ......................................................................................... 1264
Example: Legacy MB_SERVER Multiple TCP connections .............................................. 1264
Example: Legacy MB_CLIENT 1: Multiple requests with common TCP connection ......... 1265
Example: Legacy MB_CLIENT 2: Multiple requests with different TCP connections ........ 1266
Example: Legacy MB_CLIENT 3: Output image write request .......................................... 1267
Example: Legacy MB_CLIENT 4: Coordinating multiple requests .................................... 1268

13.9
13.9.1
13.9.2
13.9.3
13.9.3.1
13.9.3.2
13.9.3.3
13.9.4
13.9.4.1
13.9.4.2

Legacy Modbus RTU communication (CM/CB 1241 only) ................................................ 1269
Overview ............................................................................................................................ 1269
Selecting the version of the Modbus RTU instructions ...................................................... 1269
Legacy Modbus RTU instructions ...................................................................................... 1270
MB_COMM_LOAD (Configure port on the PtP module for Modbus RTU) ........................ 1270
MB_MASTER (Communicate using the PtP port as Modbus RTU master) ...................... 1272
MB_SLAVE (Communicate using the PtP port as Modbus RTU slave) ............................ 1278
Legacy Modbus RTU examples ......................................................................................... 1285
Example: Legacy Modbus RTU master program............................................................... 1285
Example: Legacy Modbus RTU slave program ................................................................. 1287

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

13.10
13.10.1
13.10.2
13.10.3
13.10.4
13.10.5
13.10.6
13.10.7
14

TeleService communication (SMTP email) .........................................................................................1301
14.1

Industrial Remote Communication (IRC) ............................................................................1288
Telecontrol CPs overview ...................................................................................................1288
Connection to a GSM network ............................................................................................1291
Applications of the CP 1242-7 ............................................................................................1293
Other properties of the CP 1242-7......................................................................................1294
Further information..............................................................................................................1294
Accessories .........................................................................................................................1295
Configuration examples for telecontrol ...............................................................................1296
TM_Mail (Send email) instruction .......................................................................................1301

Online and diagnostic tools ................................................................................................................1309
15.1

Status LEDs ........................................................................................................................1309

15.2

Going online and connecting to a CPU...............................................................................1313

15.3

Assigning a name to a PROFINET IO device online ..........................................................1314

15.4

Setting the IP address and time of day ...............................................................................1316

15.5

Resetting to factory settings ...............................................................................................1317

15.6

Updating firmware ...............................................................................................................1318

15.7

Formatting a SIMATIC memory card from STEP 7 ............................................................1320

15.8

CPU operator panel for the online CPU..............................................................................1321

15.9

Monitoring the cycle time and memory usage ....................................................................1321

15.10

Displaying diagnostic events in the CPU ............................................................................1322

15.11

Comparing offline and online CPUs ....................................................................................1323

15.12

Performing an online/offline topology comparison ..............................................................1324

15.13
15.13.1
15.13.2
15.13.3
15.13.4
15.13.4.1
15.13.4.2
15.13.5
15.13.5.1
15.13.5.2

Monitoring and modifying values in the CPU ......................................................................1325
Going online to monitor the values in the CPU ...................................................................1326
Displaying status in the program editor ..............................................................................1327
Capturing a snapshot of the online values of a DB for restoring values.............................1327
Using a watch table to monitor and modify values in the CPU ...........................................1329
Using a trigger when monitoring or modifying PLC tags ....................................................1330
Enabling outputs in STOP mode ........................................................................................1331
Forcing values in the CPU ..................................................................................................1332
Using the force table ...........................................................................................................1332
Operation of the Force function ..........................................................................................1333

15.14
15.14.1
15.14.2
15.14.3
15.14.4
15.14.5
15.14.6
15.14.7

Downloading in RUN mode ................................................................................................1335
Prerequisites for "Download in RUN mode" .......................................................................1336
Changing your program in RUN mode ...............................................................................1337
Downloading selected blocks .............................................................................................1338
Downloading a single selected block with a compile error in another block.......................1340
Modifying and downloading existing blocks in RUN mode .................................................1341
System reaction if the download process fails ....................................................................1344
Considerations when downloading in RUN mode ..............................................................1345

15.15

Tracing and recording CPU data on trigger conditions .......................................................1347

15.16

Determining the type of wire break condition from an SM 1231 module ............................1349

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

15.17
15.17.1
15.17.2
15.17.3
A

Backing up and restoring a CPU........................................................................................ 1352
Backup and restore options ............................................................................................... 1352
Backing up an online CPU ................................................................................................. 1354
Restoring a CPU ................................................................................................................ 1356

Technical specifications ..................................................................................................................... 1359
A.1

Siemens Online Support website ....................................................................................... 1359

A.2

General technical specifications ........................................................................................ 1359

A.3

PROFINET interface X1 port pinouts ................................................................................. 1369

A.4
A.4.1
A.4.2
A.4.3
A.4.4
A.4.4.1
A.4.4.2
A.4.4.3
A.4.5

CPU 1211C ........................................................................................................................ 1370
General specifications and features................................................................................... 1370
Timers, counters, and code blocks supported by CPU 1211C .......................................... 1372
Digital inputs and outputs ................................................................................................... 1376
Analog inputs ..................................................................................................................... 1377
Step response of the built-in analog inputs of the CPU ..................................................... 1378
Sample time for the built-in analog ports of the CPU......................................................... 1378
Measurement ranges of the analog inputs for voltage (CPUs) .......................................... 1378
CPU 1211C wiring diagrams.............................................................................................. 1379

A.5
A.5.1
A.5.2
A.5.3
A.5.4
A.5.4.1
A.5.4.2
A.5.4.3
A.5.5

CPU 1212C ........................................................................................................................ 1382
General specifications and features................................................................................... 1382
Timers, counters, and code blocks supported by CPU 1212C .......................................... 1384
Digital inputs and outputs ................................................................................................... 1388
Analog inputs ..................................................................................................................... 1390
Step response of the built-in analog inputs of the CPU ..................................................... 1390
Sample time for the built-in analog ports of the CPU......................................................... 1391
Measurement ranges of the analog inputs for voltage (CPUs) .......................................... 1391
CPU 1212C wiring diagrams.............................................................................................. 1392

A.6
A.6.1
A.6.2
A.6.3
A.6.4
A.6.4.1
A.6.4.2
A.6.4.3
A.6.5

CPU 1214C ........................................................................................................................ 1395
General specifications and features................................................................................... 1395
Timers, counters and code blocks supported by CPU 1214C ........................................... 1397
Digital inputs and outputs ................................................................................................... 1401
Analog inputs ..................................................................................................................... 1403
Step response of the built-in analog inputs of the CPU ..................................................... 1403
Sample time for the built-in analog ports of the CPU......................................................... 1404
Measurement ranges of the analog inputs for voltage (CPUs) .......................................... 1404
CPU 1214C wiring diagrams.............................................................................................. 1405

A.7
A.7.1
A.7.2
A.7.3
A.7.4
A.7.4.1
A.7.4.2
A.7.4.3
A.7.4.4
A.7.5

CPU 1215C ........................................................................................................................ 1409
General specifications and features................................................................................... 1409
Timers, counters and code blocks supported by CPU 1215C ........................................... 1411
Digital inputs and outputs ................................................................................................... 1415
Analog inputs and outputs ................................................................................................. 1417
Step response of built-in analog inputs of the CPU ........................................................... 1417
Sample time for the built-in analog ports of the CPU......................................................... 1418
Measurement ranges of the analog inputs for voltage (CPUs) .......................................... 1418
Analog output specifications .............................................................................................. 1419
CPU 1215C wiring diagrams.............................................................................................. 1420

A.8
A.8.1
A.8.2

CPU 1217C ........................................................................................................................ 1425
General specifications and features................................................................................... 1425
Timers, counters and code blocks supported by CPU 1217C ........................................... 1427
S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

A.8.3
A.8.4
A.8.4.1
A.8.4.2
A.8.4.3
A.8.4.4
A.8.4.5
A.8.5
A.8.6
A.8.7

Digital inputs and outputs ...................................................................................................1430
Analog inputs and outputs ..................................................................................................1435
Analog input specifications .................................................................................................1435
Step response of built-in analog inputs of the CPU ............................................................1435
Sample time for the built-in analog ports of the CPU .........................................................1436
Measurement ranges of the analog inputs for voltage (CPUs)...........................................1436
Analog output specifications ...............................................................................................1436
CPU 1217C wiring diagrams ..............................................................................................1438
CPU 1217C Differential Input (DI) detail and application example .....................................1440
CPU 1217C Differential Output (DQ) detail and application example ................................1441

A.9
A.9.1
A.9.2
A.9.3
A.9.4
A.9.5

Digital signal modules (SMs) ..............................................................................................1442
SM 1221 digital input specifications ....................................................................................1442
SM 1222 8-point digital output specifications .....................................................................1444
SM 1222 16-point digital output specifications ...................................................................1446
SM 1223 digital input/output V DC specifications ...............................................................1451
SM 1223 digital input/output V AC specifications ...............................................................1456

A.10
A.10.1
A.10.2
A.10.3
A.10.4
A.10.5
A.10.6
A.10.7

Analog signal modules (SMs) .............................................................................................1459
SM 1231 analog input module specifications .....................................................................1459
SM 1232 analog output module specifications ...................................................................1464
SM 1234 analog input/output module specifications ..........................................................1466
Step response of the analog inputs ....................................................................................1470
Sample time and update times for the analog inputs .........................................................1470
Measurement ranges of the analog inputs for voltage and current (SB and SM) ..............1471
Measurement ranges of the analog outputs for voltage and current (SB and SM) ............1472

A.11
A.11.1
A.11.1.1
A.11.1.2
A.11.2
A.11.2.1

Thermocouple and RTD signal modules (SMs) ..................................................................1473
SM 1231 Thermocouple......................................................................................................1473
Basic operation for a thermocouple ....................................................................................1476
Selection tables for the SM 1231 thermocouple .................................................................1477
SM 1231 RTD .....................................................................................................................1479
Selection tables for the SM 1231 RTD ...............................................................................1482

A.12
A.12.1
A.12.1.1
A.12.1.2
A.12.1.3
A.12.1.4

Technology modules ...........................................................................................................1485
SM 1278 4xIO-Link Master SM ...........................................................................................1485
SM 1278 4xIO-Link Master overview ..................................................................................1488
Connecting ..........................................................................................................................1491
Parameters/address space .................................................................................................1493
Interrupt, error, and system alarms .....................................................................................1496

A.13
A.13.1
A.13.2
A.13.3
A.13.4

Digital signal boards (SBs) .................................................................................................1500
SB 1221 200 kHz digital input specifications ......................................................................1500
SB 1222 200 kHz digital output specifications ....................................................................1502
SB 1223 200 kHz digital input / output specifications .........................................................1505
SB 1223 2 X 24 V DC input / 2 X 24 V DC output specifications .......................................1508

A.14
A.14.1
A.14.2
A.14.3
A.14.3.1
A.14.3.2
A.14.3.3
A.14.3.4

Analog signal boards (SBs) ................................................................................................1511
SB 1231 1 analog input specifications ................................................................................1511
SB 1232 1 analog output specifications..............................................................................1514
Measurement ranges for analog inputs and outputs ..........................................................1516
Step response of the analog inputs ....................................................................................1516
Sample time and update times for the analog inputs .........................................................1516
Measurement ranges of the analog inputs for voltage and current (SB and SM) ..............1516
Measurement ranges of the analog outputs for voltage and current (SB and SM) ............1517

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

A.14.4
A.14.4.1
A.14.4.2
A.14.5
A.14.5.1
A.14.5.2

Thermocouple signal boards (SBs).................................................................................... 1519
SB 1231 1 analog thermocouple input specifications ........................................................ 1519
Basic operation for a thermocouple ................................................................................... 1520
RTD signal boards (SBs) ................................................................................................... 1523
SB 1231 1 analog RTD input specifications ...................................................................... 1523
Selection tables for the SB 1231 RTD ............................................................................... 1526

A.15

BB 1297 Battery board ....................................................................................................... 1528

A.16
A.16.1
A.16.1.1
A.16.1.2
A.16.1.3
A.16.1.4
A.16.2
A.16.2.1
A.16.2.2
A.16.2.3
A.16.3
A.16.3.1
A.16.3.2
A.16.4
A.16.4.1
A.16.4.2
A.16.4.3

Communication interfaces ................................................................................................. 1530
PROFIBUS ......................................................................................................................... 1530
CM 1242-5 PROFIBUS DP SLAVE ................................................................................... 1530
Pinout of the D-sub socket of the CM 1242-5 .................................................................... 1531
CM 1243-5 PROFIBUS DP Master .................................................................................... 1532
Pinout of the D-sub socket of the CM 1243-5 .................................................................... 1533
CP 1242-7 .......................................................................................................................... 1534
CP 1242-7 GPRS ............................................................................................................... 1534
GSM/GPRS antenna ANT794-4MR................................................................................... 1536
Flat antenna ANT794-3M ................................................................................................... 1537
CM 1243-2 AS-i master ..................................................................................................... 1538
Technical data for the AS-i master CM 1243-2 .................................................................. 1538
Electrical connections of the AS-i master .......................................................................... 1539
RS232, RS422, and RS485 ............................................................................................... 1541
CB 1241 RS485 specifications .......................................................................................... 1541
CM 1241 RS232 specifications .......................................................................................... 1543
CM 1241 RS422/485 specifications ................................................................................... 1544

A.17

TeleService (TS Adapter and TS Adapter modular) .......................................................... 1546

A.18

SIMATIC memory cards ..................................................................................................... 1546

A.19

Input simulators .................................................................................................................. 1547

A.20

S7-1200 Potentiometer module ......................................................................................... 1549

A.21

I/O expansion cable ........................................................................................................... 1550

A.22
A.22.1
A.22.2
A.22.3
A.22.4
A.22.5
A.22.6

Companion products .......................................................................................................... 1551
PM 1207 power module ..................................................................................................... 1551
CSM 1277 compact switch module.................................................................................... 1551
CM CANopen module ........................................................................................................ 1552
RF120C communications module ...................................................................................... 1552
SM 1238 Energy meter module ......................................................................................... 1553
SIWAREX electronic weighing systems ............................................................................ 1553

Calculating a power budget ................................................................................................................ 1555

Ordering Information .......................................................................................................................... 1559
C.1

CPU modules ..................................................................................................................... 1559

C.2

Signal modules (SMs), signal boards (SBs), and battery boards (BBs) ............................ 1560

C.3

Communication .................................................................................................................. 1561

C.4

Fail-Safe CPUs and signal modules .................................................................................. 1563

C.5

Other modules.................................................................................................................... 1563

C.6

Memory cards .................................................................................................................... 1563

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

C.7

Basic HMI devices ..............................................................................................................1564

C.8

Spare parts and other hardware .........................................................................................1564

C.9

Programming software ........................................................................................................1569

Device exchange and spare parts compatibility ..................................................................................1571
D.1

Exchanging a V3.0 CPU for a V4.2 CPU ............................................................................1571

D.2

S7-1200 V3.0 and earlier terminal block spare kits ............................................................1578

Index..................................................................................................................................................1581

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Table of contents

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Product overview
1.1

Introducing the S7-1200 PLC
The S7-1200 controller provides the flexibility and power to control a wide variety of devices
in support of your automation needs. The compact design, flexible configuration, and
powerful instruction set combine to make the S7-1200 a perfect solution for controlling a
wide variety of applications.
The CPU combines a microprocessor, an integrated power supply, input and output circuits,
built-in PROFINET, high-speed motion control I/O, and on-board analog inputs in a compact
housing to create a powerful controller. After you download your program, the CPU contains
the logic required to monitor and control the devices in your application. The CPU monitors
the inputs and changes the outputs according to the logic of your user program, which can
include Boolean logic, counting, timing, complex math operations, motion control, and
communications with other intelligent devices.
The CPU provides a PROFINET port for communication over a PROFINET network.
Additional modules are available for communicating over PROFIBUS, GPRS, RS485,
RS232, RS422, IEC, DNP3, and WDC (Wideband Data Communication) networks.

① Power connector
② Memory card slot under top
door

③ Removable user wiring connectors (behind the doors)

④ Status LEDs for the onboard I/O

⑤ PROFINET connector (on
the bottom of the CPU)

Several security features help protect access to both the CPU and the control program:
● Every CPU provides password protection (Page 210) that allows you to configure access
to the CPU functions.
● You can use "know-how protection" (Page 213) to hide the code within a specific block.
● You can use copy protection (Page 214) to bind your program to a specific memory card
or CPU.

S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK

Product overview
1.1 Introducing the S7-1200 PLC
Table 1- 1

Comparing the CPU models

Feature

CPU 1211C

Physical size (mm)
User memory

Local on-board I/O

CPU 1212C

CPU 1214C

90 x 100 x 75

CPU 1215C

CPU 1217C

110 x 100 x 75

130 x 100 x 75

150 x 100 x 75

Work

50 Kbytes

75 Kbytes

100 Kbytes

125 Kbytes

150 Kbytes

Load

1 Mbyte

2 Mbytes

4 Mbytes

Retentive

10 Kbytes

Digital

6 inputs/
4 outputs

8 inputs/
6 outputs

14 inputs/
10 output

Analog

2 inputs

Process image size Inputs (I)

2 inputs/2 output

1024 bytes

Outputs (Q) 1024 bytes
Bit memory (M)

4096 bytes

8192 bytes

Signal module (SM) expansion

None

Signal board (SB), Battery board
(BB), or communication board
(CB)

Communication module (CM)
(left-side expansion)

High-speed counters

Total

Up to 6 configured to use any built-in or SB inputs

1 MHz

100/180
kHz

Ia.0 to Ia.5

30/120 kHz

Ib.2 to Ib.5

Ia.6 to Ia.7

Ia.6 to Ib.5

Ia.6 to Ib.1

200 kHz3
Pulse outputs2

Total

Up to 4 configured to use any built-in or SB outputs

1 MHz

Qa.0 to Qa.3

100 kHz

Qa.0 to Qa.3

Qa.4 to Qb.1

20 kHz

Memory card
Data logs

Qa.4 to Qa.5

Qa.4 to Qb.1

SIMATIC memory card (optional)
Number

Maximum 8 open at one time

Size

500 MB per data log or as limited by maximum available load memory

Real time clock retention time

20 days, typ./12 day min. at 40 degrees C (maintenance-free Super Capacitor)

PROFINET
Ethernet communication port

Real math execution speed

2.3 μs/instruction

Boolean execution speed

0.08 μs/instruction

The slower speed is applicable when the HSC is configured for quadrature mode of operation.

For CPU models with relay outputs, you must install a digital signal (SB) to use the pulse outputs.

Up to 200 kHz are available with the SB 1221 DI x 24 V DC 200 kHz and SB 1221 DI 4 x 5 V DC 200 kHz.

The different CPU models provide a diversity of features and capabilities that help you create
effective solutions for your varied applications. For detailed information about a specific
CPU, see the technical specifications (Page 1359).

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Product overview
1.1 Introducing the S7-1200 PLC
Table 1- 2

Blocks, timers, and counters supported by S7-1200

Element
Blocks

Description
Type
Size

OB, FB, FC, DB
CPU Model

CPU 1211C CPU 1212C CPU 1214C CPU 1215C CPU 1217C

Code blocks

50KB

64KB

Linked1 data blocks

50KB

75KB

100KB

125KB

150KB

Unlinked2 data blocks

256KB

Quantity

Up to 1024 blocks total (OBs + FBs + FCs + DBs)

Nesting depth

16 from the program cycle or startup OB;
6 from any interrupt event OB

OBs

Timers

Counters

Monitoring

Status of 2 code blocks can be monitored simultaneously

Program cycle

Multiple

Startup

Multiple

Time-delay interrupts

4 (1 per event)

Cyclic interrupts

4 (1 per event)

Hardware interrupts

50 (1 per event)

Time error interrupts

Diagnostic error interrupts

Pull or plug of modules

Rack or station failure

Time of day

Multiple

Status

Update

Profile

Type

IEC

Quantity

Limited only by memory size

Storage

Structure in DB, 16 bytes per timer

Type

IEC

Quantity

Limited only by memory size

Storage

Structure in DB, size dependent upon count type

Stored in work memory and load memory

Stored only in load memory

•

SInt, USInt: 3 bytes

•

Int, UInt: 6 bytes

•

DInt, UDInt: 12 bytes

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Product overview
1.2 Expansion capability of the CPU

1.2

Expansion capability of the CPU
The S7-1200 family provides a variety of modules and plug-in boards for expanding the
capabilities of the CPU with additional I/O or other communication protocols. For detailed
information about a specific module, see the technical specifications (Page 1359).

①
②
③
④

Communication module (CM) or communication processor (CP) (Page 1530)
CPU (CPU 1211C (Page 1370), CPU 1212C (Page 1382), CPU 1214C (Page 1395),
CPU 1215C (Page 1409), CPU 1217C (Page 1425))
Signal board (SB) (digital SB (Page 1500), analog SB (Page 1511)), communication board
(CB) (Page 1541), or Battery Board (BB) CPU (CPU 1211C, CPU 1212C, CPU 1214C, CPU
1215C, CPU 1217C) (Page 1528)
Signal module (SM) (digital SM (Page 1442), analog SM (Page 1459), thermocouple SM
(Page 1473), RTD SM (Page 1479), technology SM) (Page 1485)

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Product overview
1.2 Expansion capability of the CPU
Table 1- 3

S7-1200 expansion modules

Type of module

Description

The CPU supports one plug-in expansion
board:
•

A signal board (SB) provides additional
I/O for your CPU. The SB connects on
the front of the CPU.

•

A communication board (CB) allows
you to add another communication port
to your CPU.

•

A battery board (BB) allows you to
provide long term backup of the
realtime clock.

① Status LEDs on the SB
② Removable user wiring connector
Signal modules (SMs) add additional functionality to the CPU. SMs connect to the
right side of the CPU.
•

Digital I/O

•

Analog I/O

•

RTD and thermocouple

•

SM 1278 IO-Link Master

•

SM 1238 Energy Meter
(https://support.industry.siemens.com/
cs/ww/en/view/109483435)

① Status LEDs
② Bus connector slide tab
③ Removable user wiring connector
Communication modules (CMs) and
communications processors (CPs) add
communication options to the CPU, such
as for PROFIBUS or RS232/RS485 connectivity (for PtP, Modbus or USS), or the
AS-i master.
A CP provides capabilities for other types
of communication, such as connecting to
the CPU over a GPRS, LTE, IEC, DNP3,
or WDC network.
•

The CPU supports up to three CMs or
CPs

•

Each CM or CP connects to the left
side of the CPU (or to the left side of
another CM or CP)

① Status LEDs
② Communication connector

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Product overview
1.3 Basic HMI panels

1.3

Basic HMI panels
The SIMATIC HMI Basic Panels provide touch-screen devices for basic operator control and
monitoring tasks. All panels have a protection rating for IP65 and have CE, UL, cULus, and
NEMA 4x certification.
The available Basic HMI panels (Page 1564)are described below:
● KTP400 Basic: 4" Touch screen with 4 configurable keys, a resolution of 480 x 272 and
800 tags
● KTP700 Basic: 7" Touch screen with 8 configurable keys, a resolution of 800 x 480 and
800 tags
● KTP700 Basic DP: 7" Touch screen with 8 configurable keys, a resolution of 800 x 480
and 800 tags
● KTP900 Basic: 9" Touch screen with 8 configurable keys, a resolution of 800 x 480 and
800 tags
● KTP1200 Basic: 12" Touch screen with 10 configurable keys, a resolution of 800 x 480
and 800 tags
● KTP 1200 Basic DP: 12" Touch screen with 10 configurable keys, a resolution of 800 x
400 and 800 tags

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New features
The following features are new in the V4.2 release:
● Enhancements to the Web server (Page 1001):
– More shared functionality with the S7-1500 Web server
– Ability to define user-defined Web page as start page
– New or improved standard Web pages:
Watch tables (Page 1033)
Online backup (Page 1035)
Communication (Page 1027): inclusion of communication statistics
● New programming instructions:
– Basic instructions:
LOWER_BOUND: (Read out ARRAY low limit) (Page 277)
UPPER_BOUND: (Read out ARRAY high limit) (Page 279)
– Extended instructions
GetSymbolName (Read out a tag on the input parameter) (Page 370)

GetSymbolPath (Query composite global name of the input parameter assignment)
(Page 373)
GetInstanceName (Read out name of the block instance) (Page 376)
GetInstancePath (Query composite global name of the block instance) (Page 379)
GetBlockName (Read out name of the block) (Page 381)
GETIO (Read process image) (Page 388)
SETIO (Transfer process image) (Page 389)
GETIO_PART (Read process image area) (Page 390)
SETIO_PART (Transfer process image area) (Page 392)
D_ACT_DP (Enable/disable PROFINET IO devices) (Page 398)
RCVREC (I-device/I-slave receive data record) (Page 411)
PRVREC (I-device/I-slave make data record available) (Page 413)
PROFIenergy (Page 419) instructions for energy management
Gen_UsrMsg (Generate user diagnostic alarms) (Page 436)
RD_SINFO (Read current OB start information) (Page 440)

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New features

Get_Name (Read the name of a PROFINET IO device) (Page 453)
GetStationInfo (Read the IP or MAC address of a PROFINET IO device) (Page 460)
CTRL_PTO (Pulse train output) (Page 488)
DataLogClear (Empty data log) (Page 518)
DataLogDelete (Delete data log) (Page 520)
CREATE_DB (Create data block) (Page 534)
ATTR_DB (Read data block attribute) (Page 541)
DELETE_DB (Delete data block) (Page 542)
● New communication capabilities:
– Time synchronization (Page 181)
– Media Redundancy Protocol (MRP) (Page 954) (client-only)
– S7-routing (Page 962)
– Autonegotiation (Page 814)
– PROFINET interface X1 port pinouts (Page 1369)
● New High-Speed Counter (HSC) capabilities:
– Added support to the CTRL_HSC_EXT (Control high-speed counter) instruction for
Count and Frequency mode (Page 556)
– Enable and disable the HSC with the Gate input (Page 567)
– Capture the HSC’s count value with Capture input (Page 569)
– Generate an output pulse on HSC events with the Compare output (Page 570)
– Ability to change HSC counting limits and an additional reference value (Page 578)
– Improved accuracy of frequency measurement (Page 573)
● New motion control capabilities:
– Speed controlled operation (Page 681)
– Telegram 4 support (Page 684)
– Simulation axis (Page 689)
– Data adaptation (Page 691)
– Axis control using the TM Pulse module (Page 702)
– Homing reference point switch level (Page 726)
– Hardware limit switch edge detection configuration on address change (Page 716)
● Backup and restore of an online S7-1200 CPU from STEP 7 (Page 1352)
● Enhancements to capturing and loading an online DB snapshot (Page 1327)
● Opportunity to synchronize the online CPU with the offline project (Page 219) under
certain conditions
● Reduction of repeated security event entries in the Diagnostics Buffer (Page 114)
● Ability to format a SIMATIC memory card from STEP 7 (Page 1320)
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New features

● Ability to prevent copies from internal load memory to external load memory (SIMATIC
memory card) (Page 212)
● Support for the 3964R protocol (Page 1092) in point-to-point communications
● Ability to declare a tag in I or Q memory using a PLC data type (Page 133) (user-defined
data type or UDT)
● Ability to save trace job measurements (Page 1347) to external load memory
● Maximum size of 256KB for unlinked (load memory) data blocks, regardless of CPU
model (Page 27)

New modules for the S7-1200
New modules expand the power of the S7-1200 CPU and provide the flexibility to meet your
automation needs:
● New Fail-safe CPUs (https://support.industry.siemens.com/cs/ww/en/view/104547552):
There are two new fail-safe CPUs in conjunction with the S7-1200 V4.2 or later release:
– CPU 1212FC DC/DC/DC (6ES7212-1AF40-0XB0)
– CPU 1212FC DC/DC/Rly (6ES7212-1HF40-0XB0)
● The SM 1238 Energy Meter 480 V AC (6ES7238-5XA32-0XB0)
(https://support.industry.siemens.com/cs/ww/en/view/109483435) supports machine-level
deployment with an S7-1200 CPU V4.1 or later, including the Fail-safe CPUs. It records
over 200 different electrical measurement and energy values and lets you create
transparency about the energy requirements of individual components of a production
plant down to the machine level. Using the measured values provided by the SM 1238
Energy meter module, you can determine energy consumption and power demand.

Exchanging your V3.0 CPU for a V4.2 CPU
If you are replacing an S7-1200 V3.0 CPU with an S7-1200 V4.2 CPU, take note of the
documented differences (Page 1571) in the versions and the required user actions.

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New features

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STEP 7 programming software

STEP 7 provides a user-friendly environment to develop, edit, and monitor the logic needed
to control your application, including the tools for managing and configuring all of the devices
in your project, such as controllers and HMI devices. To help you find the information you
need, STEP 7 provides an extensive online help system.
STEP 7 provides standard programming languages for convenience and efficiency in
developing the control program for your application.
● LAD (ladder logic) (Page 199) is a graphical programming language. The representation
is based on circuit diagrams.
● FBD (Function Block Diagram) (Page 200) is a programming language that is based on
the graphical logic symbols used in Boolean algebra.
● SCL (structured control language) (Page 201) is a text-based, high-level programming
language.
When you create a code block, you select the programming language to be used by that
block. Your user program can utilize code blocks created in any or all of the programming
languages.
Note
STEP 7 is the programming and configuration software component of the TIA Portal. The
TIA Portal, in addition to STEP 7, also includes WinCC for designing and executing runtime
process visualization, and includes online help for WinCC as well as STEP 7.

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STEP 7 programming software
3.1 System requirements

3.1

System requirements
You must install STEP 7 with Administrator privileges.
Table 3- 1

System requirements

Hardware/software

Requirements

Processor type

Intel® Core™ i5-3320M 3.3 GHz or better

RAM

8 GB

Available hard disk space

2 GB on system drive C:\

Operating systems

You can use STEP 7 with the following operating systems (64bit only):
•

Microsoft Windows 7 Home Premium SP1 or higher (STEP 7
Basic only, not supported for STEP 7 Professional)

•

Microsoft Windows 7 or higher (Professional SP1, Enterprise
SP1, Ultimate SP1)

•

Microsoft Windows 8.1 (STEP 7 Basic only, not supported
for STEP 7 Professional)

•

Microsoft Windows 8.1 (Professional, Enterprise)

•

Microsoft Server 2008 R2 StdE SP1 (STEP 7 Professional
only)

•

Microsoft Server 2012 R2 StdE

Graphics card

32 MB RAM
24-bit color depth

Screen resolution

1920 x 1080 (recommended)

Network

10 Mbit/s Ethernet or faster, for communication between STEP 7
and the CPU

Optical drive

DVD-ROM

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STEP 7 programming software
3.2 Different views to make the work easier

3.2

Different views to make the work easier
STEP 7 provides a user-friendly environment to develop controller logic, configure HMI
visualization, and setup network communication. To help increase your productivity, STEP 7
provides two different views of the project: a task-oriented set of portals that are organized
on the functionality of the tools (Portal view), or a project-oriented view of the elements within
the project (Project view). Choose which view helps you work most efficiently. With a single
click, you can toggle between the Portal view and the Project view.
Portal view

① Portals for the different tasks
② Tasks for the selected portal
③ Selection panel for the selected
action

④ Changes to the Project view

Project view

① Menus and toolbar
② Project navigator
③ Work area
④ Task cards
⑤ Inspector window
⑥ Changes to the Portal view
⑦ Editor bar

With all of these components in one place, you have easy access to every aspect of your
project. The work area consists of three tabbed views:
● Device view: Displays the device that you have added or selected and its associated
modules
● Network view: Displays the CPUs and network connections in your network
● Topology view: Displays the PROFINET topology of the network including devices,
passive components, ports, interconnections, and port diagnostics

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STEP 7 programming software
3.2 Different views to make the work easier
Each view also enables you to perform configuration tasks. The inspector window shows the
properties and information for the object that you have selected in the work area. As you
select different objects, the inspector window displays the properties that you can configure.
The inspector window includes tabs that allow you to see diagnostic information and other
messages.
By showing all of the editors that are open, the editor bar helps you work more quickly and
efficiently. To toggle between the open editors, simply click the different editor. You can also
arrange two editors to appear together, arranged either vertically or horizontally. This feature
allows you to drag and drop between editors.
The STEP 7 Information System provides extensive online help for all of the configuration,
programming, and monitoring tools of STEP 7. You can refer to it for detailed explanations
beyond what this manual provides.

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STEP 7 programming software
3.3 Easy-to-use tools

3.3

Easy-to-use tools

3.3.1

Inserting instructions into your user program
STEP 7 provides task cards that contain the instructions for your
program. The instructions are grouped according to function.

To create your program, you drag instructions from the task card
onto a network.

3.3.2

Accessing instructions from the "Favorites" toolbar
STEP 7 provides a "Favorites" toolbar to give you quick access to the instructions that you
frequently use. Simply click the icon for the instruction to insert it into your network!
(For the "Favorites" in the instruction tree, doubleclick the icon.)
You can easily customize the
"Favorites" by adding new instructions.
Simply drag and drop an instruction to the "Favorites".
The instruction is now just a click
away!

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.3

Creating a complex equation with a simple instruction
The Calculate instruction (Page 255) lets you create a math function that operates on multiple input parameters to produce the result, according to the equation that you define.
In the Basic instruction tree, expand the Math functions folder.
Double-click the Calculate instruction to insert the instruction
into your user program.

The unconfigured Calculate instruction provides two input parameters
and an output parameter.

Click the "???" and select the data types for the input and output parameters. (The input and output parameters must all be the same data
type.)
For this example, select the "Real" data type.

Click the "Edit equation" icon to enter the equation.

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3.3 Easy-to-use tools
For this example, enter the following equation for scaling a raw analog value. (The "In" and
"Out" designations correspond to the parameters of the Calculate instruction.)
Out value = ((Out high - Out low) / (In high - In low)) * (In value - In low) + Out low
Out
Where:

= ((in4 - in5) / (in2 - in3)) * (in1 - in3) + in5
Out value

(Out)

Scaled output value

In value

(in1)

Analog input value

In high

(in2)

Upper limit for the scaled input value

In low

(in3)

Lower limit for the scaled input value

Out high

(in4)

Upper limit for the scaled output value

Out low

(in5)

Lower limit for the scaled output value

In the "Edit Calculate" box, enter the equation with the parameter names:
OUT = ((in4 - in5) / (in2 - in3)) * (in1 - in3) + in5

When you click "OK", the Calculate
instruction creates the inputs required for the instruction.

Enter the tag names for the values
that correspond to the parameters.

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.4

Adding inputs or outputs to a LAD or FBD instruction
Some of the instructions allow you to create additional inputs or outputs.
● To add an input or output, click the "Create" icon or right-click on an input stub for one of
the existing IN or OUT parameters and select the "Insert input" command.
● To remove an input or output, right-click on the stub for one of the existing IN or OUT
parameters (when there are more than the original two inputs) and select the "Delete"
command.

3.3.5

Expandable instructions
Some of the more complex instructions are expandable, displaying only the key inputs and
outputs. To display all the inputs and outputs, click the arrow at the bottom of the instruction.

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3.3 Easy-to-use tools

3.3.6

Selecting a version for an instruction
The development and release cycles for certain sets of instructions (such as Modbus, PID
and motion) have created multiple released versions for these instructions. To help ensure
compatibility and migration with older projects, STEP 7 allows you to choose which version
of instruction to insert into your user program.
Click the icon on the instruction tree task card
to enable the headers and columns of the
instruction tree.
To change the version of the instruction, select the appropriate version from the dropdown list.

3.3.7

Modifying the appearance and configuration of STEP 7
You can select a variety of settings, such as the appearance of the interface, language, or
the folder for saving your work.
Select the "Settings" command from the "Options" menu to change these settings.

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.8

Dragging and dropping between editors
To help you perform tasks quickly and easily,
STEP 7 allows you to drag and drop elements
from one editor to another. For example, you
can drag an input from the CPU to the address
of an instruction in your user program.
You must zoom in at least 200% to select the
inputs or outputs of the CPU.
Notice that the tag names are displayed not
only in the PLC tag table, but also are displayed on the CPU.

To display two editors at one time, use the
"Split editor" menu commands or buttons in
the toolbar.

To toggle between the editors that have been opened, click the icons in the editor bar.

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.9

Changing the operating mode of the CPU
The CPU does not have a physical switch for changing the operating mode (STOP or RUN).
Use the "Start CPU" and "Stop CPU" toolbar buttons to change the operating
mode of the CPU.
When you configure the CPU in the device configuration (Page 153), you configure the startup behavior in the properties of the CPU (Page 170).
The "Online and diagnostics" portal also provides an operator panel for changing the
operating mode of the online CPU. To use the CPU operator panel, you must be connected
online to the CPU. The "Online tools" task card displays an operator panel that shows the
operating mode of the online CPU. The operator panel also allows you to change the
operating mode of the online CPU.
Use the button on the operator panel to change the operating mode
(STOP or RUN). The operator panel also provides an MRES button for
resetting the memory.

The color of the RUN/STOP indicator shows the current operating mode of the CPU. Yellow
indicates STOP mode, and green indicates RUN mode.
From the device configuration in STEP 7 (Page 153) you can also configure the default
operating mode on power up of the CPU (Page 87).
Note
You can also change the operating mode of the CPU from the Web server (Page 1001) or
the SIMATIC Automation Tool
(https://support.industry.siemens.com/cs/ww/en/view/98161300).

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.10

Changing the call type for a DB
STEP 7 allows you to easily create or change the association of a DB for an instruction or an FB that is in an FB.
• You can switch the association between different DBs.
• You can switch the association between a singleinstance DB and a multi-instance DB.
• You can create an instance DB (if an instance DB is
missing or not available).
You can access the "Change call type" command either
by right-clicking the instruction or FB in the program editor or by selecting the "Block call" command from the
"Options" menu.

The "Call options" dialog allows
you to select a single-instance
or multi-instance DB. You can
also select specific DBs from a
drop-down list of available DBs.

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.11

Temporarily disconnecting devices from a network
From the network view, you can disconnect individual network devices from the subnet.
Because the configuration of the device is not removed from the project, you can easily
restore the connection to the device.

Right-click the interface port of the network
device and select the "Disconnect from subnet" command from the context menu.

STEP 7 reconfigures the network connections, but does not remove the disconnected device
from the project. While the network connection is deleted, the interface addresses are not
changed.

When you download the new network connections, the CPU must be set to STOP mode.
To reconnect the device, simply create a new network connection to the port of the device.

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STEP 7 programming software
3.3 Easy-to-use tools

3.3.12

Virtual unplugging of devices from the configuration
STEP 7 provides a storage area for "unplugged" modules. You can drag a module
from the rack to save the configuration of
that module. These unplugged modules
are saved with your project, allowing you
to reinsert the module in the future without
having to reconfigure the parameters.
One use of this feature is for temporary
maintenance. Consider a scenario where
you might be waiting for a replacement
module and plan to temporarily use a different module as a short-term replacement. You could drag the configured
module from the rack to the "Unplugged
modules" and then insert the temporary
module.

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STEP 7 programming software
3.4 Backward compatibility

3.4

Backward compatibility
STEP 7 V14 supports configuration and programming of the S7-1200 V4.2 CPU and
provides for all of the new features (Page 33).
You can download projects for S7-1200 V4.0 and V4.1 CPUs from STEP 7 (V12 or later) to
an S7-1200 V4.2 CPU. Your configuration and program will be limited to the set of features
and instructions that the previous version of the S7-1200 CPU and your version of STEP 7
supported.
This backwards compatibility makes it possible for you to run programs on the new
S7-1200 V4.2 CPU models that you have previously designed and programmed for older
versions.
WARNING
Risks with copying and pasting program logic from older versions of STEP 7
Copying program logic from an older version of STEP 7 such as STEP 7 V12 into STEP 7
V14 can cause unpredictable behavior in program execution or failures to compile. Different
versions of STEP 7 implement program elements differently. The compiler does not always
detect the differences if you made the changes by pasting from an older version into
STEP 7 V14. Executing unpredictable program logic could result in death or severe
personal injury if you do not correct the program.
When using program logic from a release of STEP 7 earlier than STEP 7 V14, always
upgrade the entire project to STEP 7 14. Then you can copy, cut, paste, and edit program
logic as necessary. In STEP 7 V14, you can open a project from STEP 7 V13 SP1 or later.
STEP 7 then performs the necessary compatibility conversions and upgrades the program
correctly. Such upgrade conversions and corrections are necessary for proper program
compilation and execution. If your project is older than STEP 7 V13 SP1, you must upgrade
the project incrementally to STEP 7 V14 (Page 1571).
You cannot download projects for V1.0, V2.0, or V3.0 S7-1200 CPUs to an S7-1200 V4.2
CPU. See the Device exchange and spare parts compatibility (Page 1571) topic for
guidelines on upgrading older projects to a project that you can download.
Note
Projects with S7-1200 V1.x CPU versions
You cannot open a STEP 7 project that contains S7-1200 V1.x CPUs in STEP 7 V14. In
order to use your existing project, you must use STEP 7 V13 SP1 (with any update) to open
your project and convert the S7-1200 V1.x CPUs to V2.0 or later. You can then use STEP 7
V14 to open the saved project with the converted CPUs.

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3.4 Backward compatibility

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Installation
4.1

Guidelines for installing S7-1200 devices
The S7-1200 equipment is designed to be easy to install. You can install an S7-1200 either
on a panel or on a standard rail, and you can orient the S7-1200 either horizontally or
vertically. The small size of the S7-1200 allows you to make efficient use of space.
Electrical equipment standards classify the SIMATIC S7-1200 system as Open Equipment.
You must install the S7-1200 in a housing, cabinet, or electric control room. You should limit
entry to the housing, cabinet, or electric control room to authorized personnel.
The installation should provide a dry environment for the S7-1200. SELV/PELV circuits are
considered to provide protection against electric shock in dry locations.
The installation should provide the appropriate mechanical strength, flammability protection,
and stability protection that is approved for open equipment in your particular location
category according to applicable electrical and building codes.
Conductive contamination due to dust, moisture, and airborne pollution can cause
operational and electrical faults in the PLC.
If you locate the PLC in an area where conductive contamination may be present, the PLC
must be protected by an enclosure with appropriate protection rating. IP54 is one rating that
is generally used for electronic equipment enclosures in dirty environments and may be
appropriate for your application.
WARNING
Improper installation of the S7-1200 can result in electrical faults or unexpected operation
of machinery.
Electrical faults or unexpected machine operation can result in death, severe personal
injury, and/or property damage.
All instructions for installation and maintenance of a proper operating environment must be
followed to ensure the equipment operates safely.

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Installation
4.1 Guidelines for installing S7-1200 devices

Separate the S7-1200 devices from heat, high voltage, and electrical noise
As a general rule for laying out the devices of your system, always separate the devices that
generate high voltage and high electrical noise from the low-voltage, logic-type devices such
as the S7-1200.
When configuring the layout of the S7-1200 inside your panel, consider the heat-generating
devices and locate the electronic-type devices in the cooler areas of your cabinet. Reducing
the exposure to a high-temperature environment will extend the operating life of any
electronic device.
Consider also the routing of the wiring for the devices in the panel. Avoid placing low-voltage
signal wires and communications cables in the same tray with AC power wiring and highenergy, rapidly-switched DC wiring.

Provide adequate clearance for cooling and wiring
S7-1200 devices are designed for natural convection cooling. For proper cooling, you must
provide a clearance of at least 25 mm above and below the devices. Also, allow at least 25
mm of depth between the front of the modules and the inside of the enclosure.
CAUTION
For vertical mounting, the maximum allowable ambient temperature is reduced by 10
degrees C.
Orient a vertically mounted S7-1200 system as shown in the following figure.
Ensure that the S7-1200 system is mounted correctly.

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Installation
4.1 Guidelines for installing S7-1200 devices
When planning your layout for the S7-1200 system, allow enough clearance for the wiring
and communications cable connections.

①
②

Side view
Horizontal installation

③
④

Vertical installation
Clearance area

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Installation
4.2 Power budget

4.2

Power budget
Your CPU has an internal power supply that provides power for the CPU, the signal
modules, signal board and communication modules and for other 24 V DC user power
requirements.
Refer to the technical specifications (Page 1359) for information about the 5 V DC logic
budget supplied by your CPU and the 5 V DC power requirements of the signal modules,
signal boards, and communication modules. Refer to "Calculating a power budget"
(Page 1555) to determine how much power (or current) the CPU can provide for your
configuration.
The CPU provides a 24 V DC sensor supply that can supply 24 V DC for input points, for
relay coil power on the signal modules, or for other requirements. If your 24 V DC power
requirements exceed the budget of the sensor supply, then you must add an external 24 V
DC power supply to your system. Refer to the technical specifications (Page 1359) for the
24 V DC sensor supply power budget for your particular CPU.
If you require an external 24 V DC power supply, ensure that the power supply is not
connected in parallel with the sensor supply of the CPU. For improved electrical noise
protection, it is recommended that the commons (M) of the different power supplies be
connected.
WARNING
Connecting an external 24 V DC power supply in parallel with the 24 V DC sensor supply
can result in a conflict between the two supplies as each seeks to establish its own
preferred output voltage level
The result of this conflict can be shortened lifetime or immediate failure of one or both
power supplies, with consequent unpredictable operation of the PLC system. Unpredictable
operation could result in death, severe personal injury and/or property damage.
The DC sensor supply and any external power supply should provide power to different
points.
Some of the 24 V DC power input ports in the S7-1200 system are interconnected, with a
common logic circuit connecting multiple M terminals. For example, the following circuits are
interconnected when designated as "not isolated" in the data sheets: the 24 V DC power
supply of the CPU, the power input for the relay coil of an SM, or the power supply for a nonisolated analog input. All non-isolated M terminals must connect to the same external
reference potential.
WARNING
Connecting non-isolated M terminals to different reference potentials will cause unintended
current flows that may cause damage or unpredictable operation in the PLC and any
connected equipment.
Failure to comply with these guidelines could cause damage or unpredictable operation
which could result in death or severe personal injury and/or property damage.
Always ensure that all non-isolated M terminals in an S7-1200 system are connected to the
same reference potential.

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4.3 Installation and removal procedures

4.3

Installation and removal procedures

4.3.1

Mounting dimensions for the S7-1200 devices

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4.3 Installation and removal procedures
Table 4- 1

Mounting dimensions (mm)

S7-1200 Devices
CPU

Signal modules

Width A
(mm)

Width B
(mm)

Width C
(mm)

CPU 1211C and CPU 1212C

CPU 1214C

110

CPU 1215C

130

65 (top)

Bottom:
C1: 32.5
C2: 65
C3: 32.5

CPU 1217C

150

Bottom:
C1: 37.5
C2: 75
C3: 37.5

Digital 8 and 16 point

22.5

Digital DQ 8 x Relay (Changeover)

Analog 16 point

SM 1238 Energy Meter module

22.5

CM 1241 RS232, and
CM 1241 RS422/485

TS Adapter

TS Module

Analog 2, 4, and 8 point
Thermocouple 4 and 8 point
RTD 4 point
SM 1278 IO Link-Master

RTD 8 point
Communication
interfaces

CM 1243-5 PROFIBUS master and
CM 1242-5 PROFIBUS slave
CM 1242-2 AS-i Master
CP 1242-7 GPRS V2
CP 1243-7 LTE-EU
CP 1243-1 DNP3
CP 1243-1 IEC
CP 1243-1
CP1243-1 PCC
CP 1243-8 IRC
RF120C
TS (TeleService) Adapter IE Advanced 1
TS (Teleservice) Adapter IE Basic 1

Before installing the TS (TeleService) Adapter IE Advanced or IE Basic, you must first connect the
TS Adapter and a TS module. The total width ("width A") is 60 mm.

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4.3 Installation and removal procedures
Each CPU, SM, CM, and CP supports mounting on either a DIN rail or on a panel. Use the
DIN rail clips on the module to secure the device on the rail. These clips also snap into an
extended position to provide screw mounting positions to mount the unit directly on a panel.
The interior dimension of the hole for the DIN clips on the device is 4.3 mm.
A 25 mm thermal zone must be provided above and below the unit for free air circulation.

Installing and removing the S7-1200 devices
The CPU can be easily installed on a standard DIN rail or on a panel. DIN rail clips are
provided to secure the device on the DIN rail. The clips also snap into an extended position
to provide a screw mounting position for panel-mounting the unit.

①
②

DIN rail installation
DIN rail clip in latched position

③
④

Panel installation
Clip in extended position for panel mounting

Before you install or remove any electrical device, ensure that the power to that equipment
has been turned off. Also, ensure that the power to any related equipment has been turned
off.
WARNING
Installation or removal of S7-1200 or related equipment with the power applied could cause
electric shock or unexpected operation of equipment.
Failure to disable all power to the S7-1200 and related equipment during installation or
removal procedures could result in death, severe personal injury and/or property damage
due to electric shock or unexpected equipment operation.
Always follow appropriate safety precautions and ensure that power to the S7-1200 is
disabled before attempting to install or remove S7-1200 CPUs or related equipment.

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4.3 Installation and removal procedures
Always ensure that whenever you replace or install an S7-1200 device you use the correct
module or equivalent device.
WARNING
Incorrect installation of an S7-1200 module may cause the program in the S7-1200 to
function unpredictably.
Failure to replace an S7-1200 device with the same model, orientation, or order could result
in death, severe personal injury and/or property damage due to unexpected equipment
operation.
Replace an S7-1200 device with the same model, and be sure to orient and position it
correctly.
WARNING
Do not disconnect equipment when a flammable or combustible atmosphere is present.
Disconnection of equipment when a flammable or combustible atmosphere is present may
cause a fire or explosion which could result in death, serious injury and/or property
damage.
Always follow appropriate safety precautions when a flammable or combustible atmosphere
is present.
Note
Electrostatic discharge can damage the device or the receptacle on the CPU.
Make contact with a grounded conductive pad and/or wear a grounded wrist strap whenever
you handle the device.

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4.3 Installation and removal procedures

4.3.2

Installing and removing the CPU
You can install the CPU on a panel or on a DIN rail.
Note
Attach any communication modules to the CPU and install the assembly as a unit. Install
signal modules separately after the CPU has been installed.
Consider the following when installing the units on the DIN rail or on a panel:
● For DIN rail mounting, make sure the upper DIN rail clip is in the latched (inner) position
and that the lower DIN rail clip is in the extended position for the CPU and attached CMs.
● After installing the devices on the DIN rail, move the lower DIN rail clips to the latched
position to lock the devices on the DIN rail.
● For panel mounting, make sure the DIN rail clips are pushed to the extended position.
To install the CPU on a panel, follow these steps:
1. Locate, drill, and tap the mounting holes (M4), using the dimensions shown in table,
Mounting dimensions (mm) (Page 57).
2. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical power.
3. Extend the mounting clips from the module. Make sure the DIN rail clips on the top and
bottom of the CPU are in the extended position.
4. Secure the module to the panel, using a Pan Head M4 screw with spring and flat washer.
Do not use a flat head screw.
Note
The type of screw will be determined by the material upon which it is mounted. You
should apply appropriate torque until the spring washer becomes flat. Avoid applying
excessive torque to the mounting screws. Do not use a flat head screw.
Note
Using DIN rail stops could be helpful if your CPU is in an environment with high vibration
potential or if the CPU has been installed vertically. Use an end bracket (8WA1808 or
8WA1805) on the DIN rail to ensure that the modules remain connected. If your system is
in a high-vibration environment, then panel-mounting the CPU will provide a greater level
of vibration protection.

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4.3 Installation and removal procedures
Table 4- 2
Task

Installing the CPU on a DIN rail
Procedure
1. Install the DIN rail. Secure the rail to the mounting panel every 75 mm.
2. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical
power.
3. Hook the CPU over the top of the DIN rail.
4. Pull out the DIN rail clip on the bottom of the CPU to allow the CPU to fit over the rail.
5. Rotate the CPU down into position on the rail.
6. Push in the clips to latch the CPU to the rail.

Table 4- 3
Task

Removing the CPU from a DIN rail
Procedure
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical power.
2. Disconnect the I/O connectors, wiring, and cables from the
CPU (Page 68).
3. Remove the CPU and any attached communication modules
as a unit. All signal modules should remain installed.
4. If an SM is connected to the CPU, retract the bus connector:
–

Place a screwdriver beside the tab on the top of the signal module.

–

Press down to disengage the connector from the CPU.

–

Slide the tab fully to the right.

5. Remove the CPU:
–

Pull out the DIN rail clip to release the CPU from the rail.

–

Rotate the CPU up and off the rail, and remove the CPU
from the system.

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4.3 Installation and removal procedures

4.3.3
Table 4- 4

Installing and removing an SB, CB, or BB
Installing an SB, CB, or BB 1297

Task

Procedure
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical power.
2. Remove the top and bottom terminal block covers from the CPU.
3. Place a screwdriver into the slot on top of the CPU at the rear of
the cover.
4. Gently pry the cover straight up and remove it from the CPU.
5. Place the module straight down into its mounting position in the
top of the CPU.
6. Firmly press the module into position until it snaps into place.
7. Replace the terminal block covers.

Table 4- 5

Removing an SB, CB or BB 1297

Task

Procedure
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical power.
2. Remove the top and bottom terminal block covers from the CPU.
3. Remove the signal board connector (if installed) by gently disengaging with a screwdriver.
4. Place a screwdriver into the slot on top of the module.
5. Gently pry the module up to disengage it from the CPU.
6. Without using a screwdriver, remove the module straight up from
its mounting position in the top of the CPU.
7. Replace the cover onto the CPU.
8. Replace the terminal block covers.

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Installation
4.3 Installation and removal procedures

Installing or replacing the battery in the BB 1297 battery board
The BB 1297 requires battery type CR1025. The battery is not included with the BB 1297
and must be purchased. To install or replace the battery, follow these steps:
1. In the BB 1297, install a new battery with the positive side of the battery on top, and the
negative side next to the printed wiring board.
2. The BB 1297 is ready to be installed in the CPU. Follow the installation directions above
to install the BB 1297.
To replace the battery in the BB 1297:
1. Remove the BB 1297 from the CPU following the removal directions above.
2. Carefully remove the old battery using a small screwdriver. Push the battery out from
under the clip.
3. Install a new CR1025 replacement battery with the positive side of the battery on top and
the negative side next to the printed wiring board.
4. Re-install the BB 1297 battery board following the installation directions above.
WARNING
Installing an unspecified battery in the BB 1297, or otherwise connecting an unspecified
battery to the circuit can result in fire or component damage and unpredictable operation of
machinery.
Fire or unpredictable operation of machinery can result in death, severe personal injury, or
property damage.
Use only the specified CR1025 battery for backup of the Real-time clock.

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Installation
4.3 Installation and removal procedures

4.3.4
Table 4- 6

Installing and removing an SM
Installing an SM

Task

Procedure
Install your SM after installing the CPU.
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical power.
2. Remove the cover for the connector from the right side of the
CPU:
–

Insert a screwdriver into the slot above the cover.

–

Gently pry the cover out at its top and remove the cover.

3. Retain the cover for reuse.
Connect the SM to the CPU:
1. Position the SM beside the CPU.
2. Hook the SM over the top of the DIN rail.
3. Pull out the bottom DIN rail clip to allow the SM to fit over the
rail.
4. Rotate the SM down into position beside the CPU and push
the bottom clip in to latch the SM onto the rail.
Extending the bus connector makes both mechanical and electrical connections for the SM.
1. Place a screwdriver beside the tab on the top of the SM.
2. Slide the tab fully to the left to extend the bus connector into
the CPU.
Follow the same procedure to install a signal module to a signal
module.

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4.3 Installation and removal procedures
Table 4- 7
Task

Removing an SM
Procedure
You can remove any SM without removing the CPU or other SMs in place.
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical power.
2. Remove the I/O connectors and wiring from the SM (Page 68).
3. Retract the bus connector.
–

Place a screwdriver beside the tab on the top of the SM.

–

Press down to disengage the connector from the CPU.

– Slide the tab fully to the right.
If there is another SM to the right, repeat this procedure for that SM.

Remove the SM:
1. Pull out the bottom DIN rail clip to release the SM from the rail.
2. Rotate the SM up and off the rail. Remove the SM from the system.
3. If required, cover the bus connector on the CPU to avoid contamination.
Follow the same procedure to remove a signal module from a signal module.

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Installation
4.3 Installation and removal procedures

4.3.5

Installing and removing a CM or CP
Attach any communication modules to the CPU and install the assembly as a unit, as shown
in Installing and removing the CPU (Page 61).

Table 4- 8

Installing a CM or CP

Task

Procedure
1. Ensure that the CPU and all S7-1200 equipment are
disconnected from electrical power.
2. Attach the CM to the CPU before installing the assembly
as a unit to the DIN rail or panel.
3. Remove the bus cover from the left side of the CPU:
–

Insert a screwdriver into the slot above the bus cover.

–

Gently pry out the cover at its top.

4. Remove the bus cover. Retain the cover for reuse.
5. Connect the CM or CP to the CPU:
–

Align the bus connector and the posts of the CM with
the holes of the CPU

–

Firmly press the units together until the posts snap into place.

6. Install the CPU and CP on a DIN rail or panel.

Table 4- 9

Removing a CM or CP

Task

Procedure
Remove the CPU and CM as a unit from the DIN rail or panel.
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical
power.
2. Remove the I/O connectors and all wiring and cables from the CPU and CMs.
3. For DIN rail mounting, move the lower DIN rail clips on the CPU and CMs to the
extended position.
4. Remove the CPU and CMs from the DIN rail or panel.
5. Grasp the CPU and CMs firmly and pull apart.

NOTICE
Separate modules without using a tool.
Do not use a tool to separate the modules because this can damage the units.

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Installation
4.3 Installation and removal procedures

4.3.6

Removing and reinstalling the S7-1200 terminal block connector
The CPU, SB and SM modules provide removable connectors to make connecting the wiring
easy.

Table 4- 10
Task

Removing the connector
Procedure
Prepare the system for terminal block connector removal by removing the power from
the CPU and opening the cover above the connector.
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical
power.
2. Inspect the top of the connector and locate the slot for the tip of the screwdriver.
3. Insert a screwdriver into the slot.
4. Gently pry the top of the connector away from the CPU. The connector will release
with a snap.
5. Grasp the connector and remove it from the CPU.

Table 4- 11
Task

Installing the connector
Procedure
Prepare the components for terminal block installation by removing power from the
CPU and opening the cover for connector.
1. Ensure that the CPU and all S7-1200 equipment are disconnected from electrical
power.
2. Align the connector with the pins on the unit.
3. Align the wiring edge of the connector inside the rim of the connector base.
4. Press firmly down and rotate the connector until it snaps into place.
Check carefully to ensure that the connector is properly aligned and fully engaged.

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Installation
4.3 Installation and removal procedures

4.3.7

Installing and removing the expansion cable
The S7-1200 expansion cable provides additional flexibility in configuring the layout of your
S7-1200 system. Only one expansion cable is allowed per CPU system. You install the
expansion cable either between the CPU and the first SM, or between any two SMs.

Table 4- 12

Installing and removing the male connector of the expansion cable

Task

Procedure
To install the male connector:
1. Ensure that the CPU and all S7-1200 equipment are
disconnected from electrical power.
2. Push the connector into the bus connector on the right
side of the signal module or CPU.
To remove the male connector:
1. Ensure that the CPU and all S7-1200 equipment are
disconnected from electrical power.
2. Pull out the male connector to release it from the signal
module or CPU.

Table 4- 13

Installing the female connector of the expansion cable

Task

Procedure
1. Ensure that the CPU and all S7-1200 equipment are
disconnected from electrical power.
2. Place the female connector to the bus connector on the
left side of the signal module.
3. Slip the hook extension of the female connector into the
housing at the bus connector and press down slightly
to engage the hook.
4. Lock the connector into place:
–

Place a screwdriver beside the tab on the top of the
signal module.

– Slide the tab fully to the left.
To engage the connector, you must slide the connector tab
all the way to the left. The connector tab must be locked
into place.

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4.3 Installation and removal procedures

Table 4- 14

Removing the female connector of the expansion cable

Task

Procedure
1. Ensure that the CPU and all S7-1200 equipment are
disconnected from electrical power.
2. Unlock the connector:
–

Place a screwdriver beside the tab on the top of the
signal module.

–

Press down slightly and slide the tab fully to the
right.

3. Lift the connector up slightly to disengage the hook
extension.
4. Remove the female connector.

Note
Installing the expansion cable in a vibration environment
If the expansion cable is connected to modules that move, or are not firmly fixed, the cable
male end snap-on connection can gradually become loose.
Use a cable tie to fix the male end cable on the DIN-rail (or other place) to provide extra
strain relief.
Avoid using excessive force when you pull the cable during installation. Ensure the cablemodule connection is in the correct position once installation is complete.

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Installation
4.3 Installation and removal procedures

4.3.8

TS (TeleService) adapter

4.3.8.1

Connecting the TeleService adapter
Before installing the TS (TeleService) Adapter IE Basic or TS (TeleService) Adapter IE
Advanced, you must first connect the TS Adapter and a TS module.
Available TS modules:
● TS module RS232
● TS module Modem
● TS module GSM
● TS module ISDN

Note

The TS module can be damaged if you touch the contacts of the plug connector ④ of the
TS module.
Follow ESD guidelines in order to avoid damaging the TS module through electrostatic
discharge. Before connecting a TS module and TS Adapter, make sure that both are in an
idle state.

①
②
③

TS module
TS Adapter
Elements

④
⑤
⑥

Plug connector from the TS module
Cannot be opened
Ethernet port

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4.3 Installation and removal procedures

Note

Before connecting a TS module and TS adapter basic unit, ensure that the contact pins ④
are not bent.
When connecting, ensure that the male connector and guide pins are positioned correctly.
Only connect a TS module into the TS adapter. Do not force a connection of the TS adapter
to a different device, such as an S7-1200 CPU. Do not change the mechanical construction
of the connector, and do not remove or damage the guide pins.

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Installation
4.3 Installation and removal procedures

4.3.8.2

Installing the SIM card
Locate the SIM card slot on the underside of the TS module GSM.
Note
The SIM card may only be removed or inserted if the TS module GSM is de-energized.

Table 4- 15

Installing the SIM card

Task

Procedure
Use a sharp object to press the eject
button of the SIM card tray (in the
direction of the arrow) and remove the
SIM card tray.

Place the SIM card in the SIM card
tray as shown and put the SIM card
tray back into its slot.

① TS Module GSM
② SIM card
③ SIM card tray

Note
Ensure that the SIM card is correctly oriented in the card tray. Otherwise, the SIM card will
not make connection with the module, and the eject button may not remove the card tray.

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Installation
4.3 Installation and removal procedures

4.3.8.3

Installing the TS adapter unit on a DIN rail
Prerequisites: You must have connected the TS Adapter and a TS module together, and the
DIN rail must have been installed.
Note
If you install the TS unit vertically or in high-vibration environment, the TS module can
become disconnected from the TS Adapter. Use an end bracket 8WA1808 on the DIN rail to
ensure that the modules remain connected.

Table 4- 16

Installing and removing the TS Adapter

Task

Procedure
Installation:

1. Hook the TS Adapter with attached TS module ①
on the DIN rail ②.
2. Rotate the unit back until it engages.
3. Push in the DIN rail clip on each module to attach
each module to the rail.
Removal:
1. Remove the analog cable and Ethernet cable from
the underside of the TS Adapter.
2. Remove power from the TS Adapter.
3. Use a screwdriver to disengage the rail clips on
both modules.
4. Rotate the unit upwards to remove the unit from the
DIN rail.

WARNING
Safety requirements for installing or removing the TS Adapter.
Before you remove power from the unit, disconnect the grounding of the TS Adapter by
removing the analog cable and Ethernet cable. Failure to observe this precaution could
result in death, severe personal injury and/or property damage due to unexpected
equipment operation.
Always follow these requirements when installing or removing the TS Adapter.

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Installation
4.3 Installation and removal procedures

4.3.8.4

Installing the TS adapter on a panel
Prerequisites: You must have connected the TS Adapter and TS module.
1. Move the attachment slider ① to the backside of the TS Adapter and TS module in the
direction of the arrow until it engages.
2. Screw the TS Adapter and TS module to the position marked with ② to the designated
assembly wall.
The following illustration shows the TS Adapter from behind, with the attachment sliders ①
in both positions:

①
②

Attachment slider
Drill holes for wall mounting

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Installation
4.4 Wiring guidelines

4.4

Wiring guidelines
Proper grounding and wiring of all electrical equipment is important to help ensure the
optimum operation of your system and to provide additional electrical noise protection for
your application and the S7-1200. Refer to the technical specifications (Page 1359) for the
S7-1200 wiring diagrams.

Prerequisites
Before you ground or install wiring to any electrical device, ensure that the power to that
equipment has been turned off. Also, ensure that the power to any related equipment has
been turned off.
Ensure that you follow all applicable electrical codes when wiring the S7-1200 and related
equipment. Install and operate all equipment according to all applicable national and local
standards. Contact your local authorities to determine which codes and standards apply to
your specific case.
WARNING
Installation or wiring the S7-1200 or related equipment with power applied could cause
electric shock or unexpected operation of equipment.
Failure to disable all power to the S7-1200 and related equipment during installation or
removal procedures could result in death, severe personal injury, and/or damage due to
electric shock or unexpected equipment operation.
Always follow appropriate safety precautions and ensure that power to the S7-1200 is
disabled before attempting to install or remove the S7-1200 or related equipment.
Always take safety into consideration as you design the grounding and wiring of your S71200 system. Electronic control devices, such as the S7-1200, can fail and can cause
unexpected operation of the equipment that is being controlled or monitored. For this reason,
you should implement safeguards that are independent of the S7-1200 to protect against
possible personal injury or equipment damage.
WARNING
Control devices can fail in an unsafe condition, resulting in unexpected operation of
controlled equipment.
Such unexpected operations could result in death, severe personal injury and/or property
damage.
Use an emergency stop function, electromechanical overrides, or other redundant
safeguards that are independent of the S7-1200.

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Guidelines for isolation
S7-1200 AC power supply boundaries and I/O boundaries to AC circuits have been designed
and approved to provide safe separation between AC line voltages and low voltage circuits.
These boundaries include double or reinforced insulation, or basic plus supplementary
insulation, according to various standards. Components which cross these boundaries such
as optical couplers, capacitors, transformers, and relays have been approved as providing
safe separation. Only circuits rated for AC line voltage include safety isolation to other
circuits. Isolation boundaries between 24 V DC circuits are functional only, and you should
not depend on these boundaries for safety.
The sensor supply output, communications circuits, and internal logic circuits of an S7-1200
with included AC power supply are sourced as SELV (safety extra-low voltage) according to
EN 61131-2.
To maintain the safe character of the S7-1200 low voltage circuits, external connections to
communications ports, analog circuits, and all 24 V DC nominal power supply and I/O
circuits must be powered from approved sources that meet the requirements of SELV,
PELV, Class 2, Limited Voltage, or Limited Power according to various standards.
WARNING
Use of non-isolated or single insulation supplies to supply low voltage circuits from an AC
line can result in hazardous voltages appearing on circuits that are expected to be touch
safe, such as communications circuits and low voltage sensor wiring.
Such unexpected high voltages could cause electric shock resulting in death, severe
personal injury and/or property damage.
Only use high voltage to low voltage power converters that are approved as sources of
touch safe, limited voltage circuits.

Guidelines for grounding the S7-1200
The best way to ground your application is to ensure that all the common and ground
connections of your S7-1200 and related equipment are grounded to a single point. This
single point should be connected directly to the earth ground for your system.
All ground wires should be as short as possible and should use a large wire size, such as 2
mm2 (14 AWG).
When locating grounds, consider safety-grounding requirements and the proper operation of
protective interrupting devices.

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Guidelines for wiring the S7-1200
When designing the wiring for your S7-1200, provide a single disconnect switch that
simultaneously removes power from the S7-1200 CPU power supply, from all input circuits,
and from all output circuits. Provide over-current protection, such as a fuse or circuit breaker,
to limit fault currents on supply wiring. Consider providing additional protection by placing a
fuse or other current limit in each output circuit.
Install appropriate surge suppression devices for any wiring that could be subject to lightning
surges. For more information, see Surge immunity (Page 1359) in the General technical
specifications section.
Avoid placing low-voltage signal wires and communications cables in the same wire tray with
AC wires and high-energy, rapidly switched DC wires. Always route wires in pairs, with the
neutral or common wire paired with the hot or signal-carrying wire.
Use the shortest wire possible and ensure that the wire is sized properly to carry the required
current.
Wire and cable should have a temperature rating 30 °C higher than the ambient temperature
around the S7-1200 (for example, a minimum of 85 °C-rated conductors for 55 °C ambient
temperature). You should determine other wiring type and material requirements from the
specific electrical circuit ratings and your installation environment.
Use shielded wires for optimum protection against electrical noise. Typically, grounding the
shield at the S7-1200 gives the best results. You should ground communication cable
shields to S7-1200 communication connector shells using connectors that engage the cable
shield, or by bonding the communication cable shields to a separate ground. You should
ground other cable shields using clamps or copper tape around the shield to provide a high
surface area connection to the grounding point.
When wiring input circuits that are powered by an external power supply, include an
overcurrent protection device in that circuit. External protection is not necessary for circuits
that are powered by the 24 V DC sensor supply from the S7-1200 because the sensor
supply is already current-limited.
All S7-1200 modules have removable connectors for user wiring. To prevent loose
connections, ensure that the connector is seated securely and that the wire is installed
securely into the connector.
To help prevent unwanted current flows in your installation, the S7-1200 provides isolation
boundaries at certain points. When you plan the wiring for your system, you should consider
these isolation boundaries. Refer to the technical specifications (Page 1425) for the amount
of isolation provided and the location of the isolation boundaries. Circuits rated for AC line
voltage include safety isolation to other circuits. Isolation boundaries between 24 V DC
circuits are functional only, and you should not depend on these boundaries for safety.

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A summary of Wiring rules for the S7-1200 CPUs, SMs and SBs is shown below:
Table 4- 17

Wiring rules for S7-1200 CPUs, SMs, and SBs

Wiring rules for...

CPU and SM connector

Connectible conductor
cross-sections for standard wires

2 mm2 to 0.3 mm2 (14 AWG to 22 1.3 mm2 to 0.3 mm2 (16 AWG to 22
AWG)
AWG)

SB connector

Number of wires per connection

1 or combination of 2 wires up to
2 mm2 (total)

Wire strip length

6.4 mm

6.3 to 7 mm

Tightening torque* (maximum)

0.56 N-m (5 inch-pounds)

0.33 N-m (3 inch-pounds)

Tool

2.5 to 3.0 mm flathead screwdriver

2.0 to 2.5 mm flathead screwdriver

1 or combination of 2 wires up to 1.3
mm2 (total)

* To avoid damaging the connector, be careful that you do not over-tighten the screws.

Note
Ferrules or end sleeves on stranded conductors reduce the risk of stray strands causing
short circuits. Ferrules longer than the recommended strip length should include an
insulating collar to prevent shorts due to side movement of conductors. Cross-sectional area
limits for bare conductors also apply to ferrules.

See also
Technical specifications (Page 1359)

Guidelines for lamp loads
Lamp loads are damaging to relay contacts because of the high turn-on surge current. This
surge current will nominally be 10 to 15 times the steady state current for a Tungsten lamp.
A replaceable interposing relay or surge limiter is recommended for lamp loads that will be
switched a large number of times during the lifetime of the application.

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Guidelines for inductive loads
Use suppressor circuits with inductive loads to limit the voltage rise when a control output
turns off. Suppressor circuits protect your outputs from premature failure caused by the high
voltage transient that occurs when current flow through an inductive load is interrupted.
In addition, suppressor circuits limit the electrical noise generated when switching inductive
loads. High frequency noise from poorly suppressed inductive loads can disrupt the
operation of the PLC. Placing an external suppressor circuit so that it is electrically across
the load and physically located near the load is the most effective way to reduce electrical
noise.
S7-1200 DC outputs include internal suppressor circuits that are adequate for inductive
loads in most applications. Since S7-1200 relay output contacts can be used to switch either
a DC or an AC load, internal protection is not provided.
A good suppressor solution is to use contactors and other inductive loads for which the
manufacturer provides suppressor circuits integrated in the load device, or as an optional
accessory. However, some manufacturer provided suppressor circuits may be inadequate
for your application. An additional suppressor circuit may be necessary for optimal noise
reduction and contact life.
For AC loads, a metal oxide varistor (MOV) or other voltage clamping device may be used
with a parallel RC circuit, but is not as effective when used alone. An MOV suppressor with
no parallel RC circuit often results in significant high frequency noise up to the clamp
voltage.
A well-controlled turn-off transient will have a ring frequency of no more than 10 kHz, with
less than 1 kHz preferred. Peak voltage for AC lines should be within +/- 1200 V of ground.
Negative peak voltage for DC loads using the PLC internal suppression will be ~40 V below
the 24 V DC supply voltage. External suppression should limit the transient to within 36 V of
the supply to unload the internal suppression.
Note
The effectiveness of a suppressor circuit depends on the application and must be verified for
your particular usage. Ensure that all components are correctly rated and use an
oscilloscope to observe the turn-off transient.

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Typical suppressor circuit for DC or relay outputs that switch DC inductive loads
In most applications, the addition of a diode (A)
across a DC inductive load is suitable, but if your
application requires faster turn-off times, then the
addition of a zener diode (B) is recommended. Be
sure to size your zener diode properly for the amount
of current in your output circuit.

① 1N4001 diode or equivalent
② 8.2 V Zener (DC outputs),
36 V Zener (Relay outputs)

③ Output point
④ M, 24 V reference
Typical suppressor circuit for relay outputs that switch AC inductive loads
Ensure that the working voltage of the metal oxide
varistor (MOV) is at least 20% greater than the nominal line voltage.

① See table for C value
② See table for R value
③ Output point

Choose pulse-rated, non-inductive resistors, and
capacitors recommended for pulse applications (typically metal film). Verify the components meet average power, peak power, and peak voltage
requirements.

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If you design your own suppressor circuit, the following table suggests resistor and capacitor
values for a range of AC loads. These values are based on calculations with ideal
component parameters. I rms in the table refers to the steady-state current of the load when
fully ON.
Table 4- 18

AC suppressor circuit resistor and capacitor values
Inductive load

I rms

230 V AC

Suppressor values
120 V AC

Resistor

Capacitor

Amps

W (power rating)

0.02

4.6

2.4

15000

0.1

0.05

11.5

5600

0.25

470

0.1

2700

0.5

100

0.2

1500

150

0.5

115

560

2.5

470

230

120

270

1000

460

240

150

1500

Conditions satisfied by the table values:
Maximum turn-off transition step < 500 V
Resistor peak voltage < 500 V
Capacitor peak voltage < 1250 V
Suppressor current < 8% of load current (50 Hz)
Suppressor current < 11% of load current (60 Hz)
Capacitor dV/dt < 2 V/μs
Capacitor pulse dissipation : ∫(dv/dt)2 dt < 10000 V2/μs
Resonant frequency < 300 Hz
Resistor power for 2 Hz max switching frequency
Power factor of 0.3 assumed for typical inductive load

Guidelines for differential inputs and outputs
Differential inputs and outputs behave differently than standard inputs and outputs. There
are two pins per differential input and output. Determining whether a differential input or
output is on or off requires that you measure the voltage difference between these two pins.
See the detailed specifications for the CPU 1217C in Appendix A (Page 1425).

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Execution of the user program
The CPU supports the following types of code blocks that allow you to create an efficient
structure for your user program:
● Organization blocks (OBs) define the structure of the program. Some OBs have
predefined behavior and start events, but you can also create OBs with custom start
events.
● Functions (FCs) and function blocks (FBs) contain the program code that corresponds to
specific tasks or combinations of parameters. Each FC or FB provides a set of input and
output parameters for sharing data with the calling block. An FB also uses an associated
data block (called an instance DB) to maintain the data values for that instance of the FB
call. You can call an FB multiple times, each time with a unique instance DB. Calls to the
same FB with different instance DBs do not affect the data values in any of the other
instance DBs.
● Data blocks (DBs) store data that can be used by the program blocks.
Execution of the user program begins with one or more optional startup organization blocks
(OBs) which execute once upon entering RUN mode, followed by one or more program cycle
OBs that execute cyclically. You can also associate an OB with an interrupt event, which can
be either a standard event or an error event. These OBs execute whenever the
corresponding standard or error event occurs.
A function (FC) or a function block (FB) is a block of program code that can be called from
an OB or from another FC or FB, down to the following nesting depths:
● 16 from the program cycle or startup OB
● 6 from any interrupt event OB
FCs are not associated with any particular data block (DB). FBs are tied directly to a DB and
use the DB for passing parameters and storing interim values and results.
The size of the user program, data, and configuration is limited by the available load memory
and work memory in the CPU. There is no specific limit to the number of each individual OB,
FC, FB and DB block. However, the total number of blocks is limited to 1024.
Each cycle includes writing the outputs, reading the inputs, executing the user program
instructions, and performing background processing. The cycle is referred to as a scan cycle
or scan.

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Your S7-1200 automation solution can consist of a central rack with the S7-1200 CPU and
additional modules. The term "central rack" refers to either the rail or panel installation of the
CPU and associated modules. The modules (SM, SB, BB, CB, CM or CP) are detected and
logged in only upon powerup.
● Inserting or removing a module in the central rack under power (hot) is not supported.
Never insert or remove a module from the central rack when the CPU has power.
WARNING
Safety requirements for inserting or removing modules
Insertion or removal of a module (SM, SB, BB, CD, CM or CP) from the central rack
when the CPU has power could cause unpredictable behavior, resulting in damage to
equipment and/or injury to personnel.
Always remove power from the CPU and central rack and follow appropriate safety
precautions before inserting or removing a module from the central rack.
● You can insert or remove a SIMATIC memory card while the CPU is under power.
However, inserting or removing a memory card when the CPU is in RUN mode causes
the CPU to go to STOP mode.
NOTICE
Risks with removing memory card when CPU is in RUN mode.
Insertion or removal of a memory card when the CPU is in RUN mode causes the CPU
to go to STOP, which might result in damage to the equipment or the process being
controlled.
Whenever you insert or remove a memory card, the CPU immediately goes to STOP
mode. Before inserting or removing a memory card, always ensure that the CPU is not
actively controlling a machine or process. Always install an emergency stop circuit for
your application or process.
● If you insert or remove a module in a distributed I/O rack (AS-i, PROFINET, or
PROFIBUS) when the CPU is in RUN mode, the CPU generates an entry in the
diagnostics buffer, executes the pull or plug of modules OB if present, and by default
remains in RUN mode.

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Process image update and process image partitions
The CPU updates local digital and analog I/O points synchronously with the scan cycle using
an internal memory area called the process image. The process image contains a snapshot
of the physical inputs and outputs (the physical I/O points on the CPU, signal board, and
signal modules).
You can configure I/O points to be updated in the process image every scan cycle or when a
specific event interrupt occurs. You can also configure an I/O point to be excluded from
process image updates. For example, your process might only need certain data values
when an event such as a hardware interrupt occurs. By configuring the process image
update for these I/O points to be associated with a partition that you assign to a hardware
interrupt OB, you avoid having the CPU update data values unnecessarily every scan cycle
when your process does not need a continual update.
For I/O that is updated every scan cycle, the CPU performs the following tasks during each
scan cycle:
● The CPU writes the outputs from the process image output area to the physical outputs.
● The CPU reads the physical inputs just prior to the execution of the user program and
stores the input values in the process image input area. These values thus remain
consistent throughout the execution of the user instructions.
● The CPU executes the logic of the user instructions and updates the output values in the
process image output area instead of writing to the actual physical outputs.
This process provides consistent logic through the execution of the user instructions for a
given cycle and prevents the flickering of physical output points that might change state
multiple times in the process image output area.
For controlling whether your process updates I/O points automatically on every scan cycle,
or upon the triggering of events, the S7-1200 provides five process image partitions. The first
process image partition, PIP0, is designated for I/O that is to be automatically updated every
scan cycle, and is the default assignment. You can use the remaining four partitions, PIP1,
PIP2, PIP3, and PIP4 for assigning I/O process image updates to various interrupt events.
You assign I/O to process image partitions in Device Configuration and you assign process
image partitions to interrupt events when you create interrupt OBs (Page 188) or edit OB
properties (Page 188).
By default, when you insert a module in the device view, STEP 7 sets its I/O process image
update to "Automatic update". For I/O configured for "Automatic update", the CPU handles
the data exchange between the module and the process image area automatically during
every scan cycle.

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To assign digital or analog points to a process image partition, or to exclude I/O points from
process image updates, follow these steps:
1. View the Properties tab for the appropriate device in Device configuration.
2. Expand the selections under "General" as necessary to locate the desired I/O points.
3. Select "I/O addresses".
4. Optionally select a specific OB from the "Organization block" drop-down list.
5. From the "Process image" drop-down list, change "Automatic update" to "PIP1", "PIP2",
"PIP3", "PIP4" or "None". A selection of "None" means that you can only read from and
write to this I/O using immediate instructions. To add the points back to the process
image automatic update, change this selection back to "Automatic update".

You can immediately read physical input values and immediately write physical output
values when an instruction executes. An immediate read accesses the current state of the
physical input and does not update the process image input area, regardless of whether the
point is configured to be stored in the process image. An immediate write to the physical
output updates both the process image output area (if the point is configured to be stored in
the process image) and the physical output point. Append the suffix ":P" to the I/O address if
you want the program to immediately access I/O data directly from the physical point instead
of using the process image.
Note
Use of process image partitions
If you assign I/O to one of the process image partitions PIP1 - PIP4, and do not assign an
OB to that partition, then the CPU never updates that I/O to or from the process image.
Assigning I/O to a PIP that does not have a corresponding OB assignment, is the same as
assigning the process image to "None". You can read the I/O directly from the physical I/O
with an immediate read instruction, or write to the physical I/O with an immediate write
instruction. The CPU does not update the process image.
The CPU supports distributed I/O for PROFINET, PROFIBUS, and AS-i networks
(Page 799).

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5.1.1

Operating modes of the CPU
The CPU has three modes of operation: STOP mode, STARTUP mode, and RUN mode.
Status LEDs on the front of the CPU indicate the current mode of operation.
● In STOP mode, the CPU is not executing the program. You can download a project.
● In STARTUP mode, the startup OBs (if present) execute once. The CPU does not
process interrupt events during the startup mode.
● In RUN mode, the program cycle OBs execute repeatedly. Interrupt events can occur and
the corresponding interrupt event OBs can execute at any point within the RUN mode.
You can download some parts of a project in RUN mode (Page 1335).
The CPU supports a warm restart for entering the RUN mode. Warm restart does not include
a memory reset. The CPU initializes all non-retentive system and user data at warm restart,
and retains the values of all retentive user data.
A memory reset clears all work memory, clears retentive and non-retentive memory areas,
copies load memory to work memory, and sets outputs to the configured "Reaction to CPU
STOP". A memory reset does not clear the diagnostics buffer or the permanently saved
values of the IP address.

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You can configure the "startup after POWER ON" setting of the CPU. This configuration item
appears under the "Device configuration" for the CPU under "Startup". Upon powering up,
the CPU performs a sequence of power-up diagnostic checks and system initialization.
During system initialization the CPU deletes all non-retentive bit (M) memory and resets all
non-retentive DB contents to the initial values from load memory. The CPU retains retentive
bit (M) memory and retentive DB contents and then enters the appropriate operating mode.
Certain detected errors prevent the CPU from entering the RUN mode. The CPU supports
the following configuration choices:
● No restart (stay in STOP mode)
● Warm restart - RUN
● Warm restart - mode prior to POWER OFF

NOTICE
Repairable faults can cause the CPU to enter STOP mode.
The CPU can enter STOP mode due to repairable faults, such as failure of a
replaceable signal module, or temporary faults, such as power line disturbance or erratic
power up event. Such conditions could result in property damage.
If you have configured the CPU to "Warm restart - mode prior to POWER OFF", the
CPU goes to the operating mode it was in prior to the loss of power or fault. If the CPU
was in STOP mode at the time of power loss or fault, the CPU goes to STOP mode on
power up and stays in STOP mode until it receives a command to go to RUN mode. If
the CPU was in RUN mode at the time of power loss or fault, the CPU goes to RUN
mode on the next power up providing it detects no errors that would inhibit a transition to
RUN mode.
Configure CPUs that are intended to operate independently of a STEP 7 connection to
"Warm restart - RUN" so that the CPU can return to RUN mode on the next power cycle.

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You can change the current operating mode using the "STOP" or "RUN" commands
(Page 1321) from the online tools of the programming software. You can also include a STP
instruction (Page 310) in your program to change the CPU to STOP mode. This allows you
to stop the execution of your program based on the program logic.
● In STOP mode, the CPU handles any communication requests (as appropriate) and
performs self-diagnostics. The CPU does not execute the user program, and the
automatic updates of the process image do not occur.
● In STARTUP and RUN modes, the CPU performs the tasks shown in the following figure:

STARTUP
A

Clears the I (image) memory area

Initializes the Q output (image)
memory area with either zero, the last
value, or the substitute value, as configured, and zeroes PB, PN, and AS-i
outputs

Initializes non-retentive M memory and
data blocks to their initial value and
enables configured cyclic interrupt and
time of day events.
Executes the startup OBs.

Copies the state of the physical inputs
to I memory

Stores any interrupt events into the
queue to be processed after entering
RUN mode

Enables the writing of Q memory to the
physical outputs

RUN

①
②

Writes Q memory to the physical outputs

③

Executes the program cycle OBs

④

Performs self-test diagnostics

⑤

Processes interrupts and communications
during any part of the scan cycle

Copies the state of the physical inputs to I
memory

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STARTUP processing
Whenever the operating mode changes from STOP to RUN, the CPU clears the process
image inputs, initializes the process image outputs and processes the startup OBs. Any read
accesses to the process-image inputs by instructions in the startup OBs read zero rather
than the current physical input value. Therefore, to read the current state of a physical input
during the startup mode, you must perform an immediate read. The startup OBs and any
associated FCs and FBs are executed next. If more than one startup OB exists, each is
executed in order according to the OB number, with the lowest OB number executing first.
Each startup OB includes startup information that helps you determine the validity of
retentive data and the time-of-day clock. You can program instructions inside the startup
OBs to examine these startup values and to take appropriate action. The following startup
locations are supported by the Startup OBs:
Table 5- 1

Startup locations supported by the startup OB

Input

Data Type

Description

LostRetentive

Bool

This bit is true if the retentive data storage areas have been lost

LostRTC

Bool

This bit is true if the time-of-day clock (Real time Clock) has been
lost

The CPU also performs the following tasks during the startup processing:
● Interrupts are queued but not processed during the startup phase
● No cycle time monitoring is performed during the startup phase
● Configuration changes to HSC (high-speed counter), PWM (pulse-width modulation), and
PtP (point-to-point communication) modules can be made in startup
● Actual operation of HSC, PWM and point-to-point communication modules only occurs in
RUN
After the execution of the startup OBs finishes, the CPU goes to RUN mode and processes
the control tasks in a continuous scan cycle.

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5.1.2

Processing the scan cycle in RUN mode
For each scan cycle, the CPU writes the outputs, reads the inputs, executes the user
program, updates communication modules, and responds to user interrupt events and
communication requests. Communication requests are handled periodically throughout the
scan.
These actions (except for user interrupt events) are serviced regularly and in sequential
order. User interrupt events that are enabled are serviced according to priority in the order in
which they occur. For interrupt events, the CPU reads the inputs, executes the OB, and then
writes the outputs, using the associated process image partition (PIP), if applicable.
The system guarantees that the scan cycle will be completed in a time period called the
maximum cycle time; otherwise a time error event is generated.
● Each scan cycle begins by retrieving the current values of the digital and analog outputs
from the process image and then writing them to the physical outputs of the CPU, SB,
and SM modules configured for automatic I/O update (default configuration). When a
physical output is accessed by an instruction, both the output process image and the
physical output itself are updated.
● The scan cycle continues by reading the current values of the digital and analog inputs
from the CPU, SB, and SMs configured for automatic I/O update (default configuration),
and then writing these values to the process image. When a physical input is accessed
by an instruction, the value of the physical input is accessed by the instruction, but the
input process image is not updated.
● After reading the inputs, the user program is executed from the first instruction through
the end instruction. This includes all the program cycle OBs plus all their associated FCs
and FBs. The program cycle OBs are executed in order according to the OB number with
the lowest OB number executing first.
Communications processing occurs periodically throughout the scan, possibly interrupting
user program execution.
Self-diagnostic checks include periodic checks of the system and the I/O module status
checks.
Interrupts can occur during any part of the scan cycle, and are event-driven. When an event
occurs, the CPU interrupts the scan cycle and calls the OB that was configured to process
that event. After the OB finishes processing the event, the CPU resumes execution of the
user program at the point of interruption.

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5.1.3

Organization blocks (OBs)
OBs control the execution of the user program. Specific events in the CPU trigger the
execution of an organization block. OBs cannot call each other or be called from an FC or
FB. Only an event such as a diagnostic interrupt or a time interval can start the execution of
an OB. The CPU handles OBs according to their respective priority classes, with higher
priority OBs executing before lower priority OBs. The lowest priority class is 1 (for the main
program cycle), and the highest priority class is 26.

5.1.3.1

Program cycle OB
Program cycle OBs execute cyclically while the CPU is in RUN mode. The main block of the
program is a program cycle OB. This is where you place the instructions that control your
program and where you call additional user blocks. You can have multiple program cycle
OBs, which the CPU executes in numerical order. Main (OB 1) is the default.

Program cycle events
The program cycle event happens once during each program cycle (or scan). During the
program cycle, the CPU writes the outputs, reads the inputs and executes program cycle
OBs. The program cycle event is required and is always enabled. You might have no
program cycle OBs, or you might have multiple OBs selected for the program cycle event.
After the program cycle event occurs, the CPU executes the lowest numbered program cycle
OB (usually "Main" OB 1). The CPU executes the other program cycle OBs sequentially (in
numerical order) within the program cycle. Program execution is cyclical such that the
program cycle event occurs at the following times:
● When the last startup OB finishes execution
● When the last program cycle OB finishes execution
Table 5- 2

Start information for a program cycle OB

Input

Data type

Description

Initial_Call

Bool

True for initial call of the OB

Remanence

Bool

True if retentive data are available

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5.1.3.2

Startup OB
Startup OBs execute one time when the operating mode of the CPU changes from STOP to
RUN, including powering up in the RUN mode and in commanded STOP-to-RUN transitions.
After completion, the main "Program cycle" begins executing.

Startup events
The startup event happens one time on a STOP to RUN transition and causes the CPU to
execute the startup OBs. You can configure multiple OBs for the startup event. The startup
OBs execute in numerical order.
Table 5- 3

5.1.3.3

Start information for a startup OB

Input

Data type

Description

LostRetentive

Bool

True if retentive data are lost

LostRTC

Bool

True if date and time are lost

Time delay interrupt OB
Time delay interrupt OBs execute after a time delay that you configure.

Time delay interrupt events
You configure time delay interrupt events to occur after a specified delay time has expired.
You assign the delay time with the SRT_DINT instruction. The time delay events interrupt the
program cycle to execute the corresponding time delay interrupt OB. You can attach only
one time delay interrupt OB to a time delay event. The CPU supports four time delay events.
Table 5- 4

Start information for a time delay interrupt OB

Input

Data type

Description

Sign

Word

Identifier passed to triggering call of SRT_DINT

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5.1.3.4

Cyclic interrupt OB
Cyclic interrupt OBs execute at a specified interval. You can configure up to a total of four
cyclic interrupt events, with one OB corresponding to each cyclic interrupt event.

Cyclic interrupt events
The cyclic interrupt events allow you to configure the execution of an interrupt OB at a
configured cycle time. You configure the initial cycle time when you create the cyclic interrupt
OB. A cyclic event interrupts the program cycle and executes the corresponding cyclic
interrupt OB. Note that the cyclic interrupt event is at a higher priority class than the program
cycle event.
You can attach only one cyclic interrupt OB to a cyclic event.
You can assign a phase shift to each cyclic interrupt so that the execution of cyclic interrupts
can be offset from one another by the phase offset amount. For example, if you have a 5 ms
cyclic event and a 10 ms cyclic event, every ten milliseconds both events occur at the same
moment. If you phase shift the 5 ms event by 1 to 4 ms and the 10 ms event by 0 ms, then
the two events do not occur at the same moment.
The default phase offset is 0. To change the initial phase shift, or to change the cyclic time
for a cyclic event, follow these steps:
1. Right-click the cyclic interrupt OB in the project tree.
2. Select "Properties" from the context menu.
3. Click "Cyclic interrupt" from the "Cyclic interrupt [OB 30]" dialog, and enter the new initial
values.
The maximum phase offset is 6000 ms (6 seconds) or the maximum Cyclic time, whichever
is smaller.
You can also query and change the scan time and the phase shift from your program using
the Query cyclic interrupt (QRY_CINT) and Set cyclic interrupt (SET_CINT) instructions.
Scan time and phase shift values set by the SET_CINT instruction do not persist through a
power cycle or a transition to STOP mode; scan time and phase shift values return to the
initial values following a power cycle or a transition to STOP. The CPU supports a total of
four cyclic interrupt events.

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5.1.3.5

Hardware interrupt OB
Hardware interrupt OBs execute when the relevant hardware event occurs. A hardware
interrupt OB interrupts normal cyclic program execution in reaction to a signal from a
hardware event.

Hardware interrupt events
Changes in the hardware, such as a rising or falling edge on an input point, or an HSC (High
Speed Counter) event trigger hardware interrupt events. The S7-1200 supports one interrupt
OB for each hardware interrupt event. You enable the hardware events in the device
configuration, and assign an OB for an event in the device configuration or with an ATTACH
instruction in the user program. The CPU supports several hardware interrupt events. The
CPU model and the number of input points determine the exact events that are available.
Limits on hardware interrupt events are as follows:
Edges:
● Rising edge events: maximum of 16
● Falling edge events: maximum of 16
HSC events:
● CV=PV: maximum of 6
● Direction changed: maximum of 6
● External reset: maximum of 6
Table 5- 5

Start information for a hardware interrupt OB

Input

Data type

Description

LADDR

HW_IO

Hardware identifier of the module that triggered the hardware interrupt

USI

WORD

User structure identifier (16#0001 to 16#FFFF), reserved for future
use

IChannel

USINT

Number of the channel that triggered the interrupt

EventType

BYTE

Identifier for the module-specific event type associated with the
event triggering the interrupt, for example falling edge or rising
edge.

The bits in EventType depend on the triggering module as shown below:
Module / Submodule

Value

Process event

Onboard I/O
from
CPU or SB

16#0

Rising edge

16#1

Falling edge

HSC

16#0

HSC CV=RV1

16#1

HSC direction changed

16#2

HSC reset

16#3

HSC CV=RV2

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5.1.3.6

Time error interrupt OB
If configured, the time error interrupt OB (OB 80) executes when either the scan cycle
exceeds the maximum cycle time or a time error event occurs. If triggered, it executes,
interrupting normal cyclic program execution or any other event OB.
The occurrence of either of these events generates a diagnostic buffer entry describing the
event. The diagnostic buffer entry is generated regardless of the existence of the time error
interrupt OB.

Time error interrupt events
The occurrence of any of several different time error conditions results in a time error event:
● Scan cycle exceeds maximum cycle time
The "maximum cycle time exceeded" condition results if the program cycle does not
complete within the specified maximum scan cycle time. See the section on "Monitoring
the cycle time in the S7-1200 System Manual" (Page 109) for more information regarding
the maximum cycle time condition, how to configure the maximum scan cycle time in the
properties of the CPU, and how to reset the cycle timer.
● CPU cannot start requested OB because a second time interrupt (cyclic or time-delay)
starts before the CPU finishes execution of the first interrupt OB
● Queue overflow occurred
The "queue overflow occurred" condition results if the interrupts are occurring faster than
the CPU can process them. The CPU limits the number of pending (queued) events by
using a different queue for each event type. If an event occurs when the corresponding
queue is full, the CPU generates a time error event.
All time error events trigger the execution of the time error interrupt OB if it exists. If the time
error interrupt OB does not exist, then the device configuration of the CPU determines the
CPU reaction to the time error:
● The default configuration for time errors, such as starting a second cyclic interrupt before
the CPU has finished the execution of the first, is for the CPU to stay in RUN.
● The default configuration for exceeding the maximum time is for the CPU to change to
STOP.
The user program can extend the program cycle execution time up to ten times the
configured maximum cycle time by executing the RE_TRIGR instruction (Page 309) to
restart the cycle time monitor. However, if two "maximum cycle time exceeded" conditions
occur within the same program cycle without resetting the cycle timer, then the CPU
transitions to STOP, regardless of whether the time error interrupt OB exists. See the section
on "Monitoring the cycle time in the S7-1200 System Manual" (Page 109).

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Time error interrupt OB includes start information that helps you determine which event and
OB generated the time error. You can program instructions inside the OB to examine these
start values and to take appropriate action.
Table 5- 6

Start information for the time error OB (OB 80)

Input

Data type

Description

fault_id

BYTE

16#01 - maximum cycle time exceeded
16#02 - requested OB cannot be started
16#07 and 16#09 - queue overflow occurred

csg_OBnr

OB_ANY

Number of the OB which was being executed when the error occurred

csg_prio

UINT

Priority of the OB causing the error

To include a time error interrupt OB in your project, you must add a time error interrupt by
double-clicking "Add new block" under "Program blocks" in the tree, then choose
"Organization block", and then "Time error interrupt".
The priority for a new V4.0 CPU is 22. If you exchange a V3.0 CPU for a V4.0 CPU
(Page 1571), the priority is 26, the priority that was in effect for V3.0. In either case, the
priority field is editable and you can set the priority to any value in the range 22 to 26.

5.1.3.7

Diagnostic error interrupt OB
The diagnostic error interrupt OB executes when the CPU detects a diagnostic error, or if a
diagnostics-capable module recognizes an error and you have enabled the diagnostic error
interrupt for the module. The diagnostic error interrupt OB interrupts the normal cyclic
program execution. You can include an STP instruction in the diagnostic error interrupt OB to
put the CPU in STOP mode if you desire your CPU to enter STOP mode upon receiving this
type of error.
If you do not include a diagnostic error interrupt OB in your program, the CPU ignores the
error and stays in RUN mode.

Diagnostic error events
Analog (local), PROFINET, PROFIBUS, and some digital (local) devices are capable of
detecting and reporting diagnostic errors. The occurrence or removal of any of several
different diagnostic error conditions results in a diagnostic error event. The following
diagnostic errors are supported:
● No user power
● High limit exceeded
● Low limit exceeded
● Wire break
● Short circuit
Diagnostic error events trigger the execution of the diagnostic error interrupt OB (OB 82) if it
exists. If it does not exist, then the CPU ignores the error.

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To include a diagnostic error interrupt OB in your project, you must add a diagnostic error
interrupt by double-clicking "Add new block" under "Program blocks" in the tree, then choose
"Organization block", and then "Diagnostic error interrupt".
Note
Diagnostic errors for multi-channel local analog devices (I/O, RTD, and Thermocouple)
The diagnostic error interrupt OB can process only one channel's diagnostic error at a time.
If two channels of a multi-channel device have an error, then the second error only triggers
the diagnostic error interrupt OB under the following conditions: the first channel error clears,
the execution of the diagnostic error interrupt OB that the first error triggered is complete,
and the second error still exists.
The diagnostic error interrupt OB includes startup information that helps you determine
whether the event is due to the occurrence or removal of an error, and the device and
channel which reported the error. You can program instructions inside the diagnostic error
interrupt OB to examine these startup values and to take appropriate action.
Note
Diagnostic error OB Start information references the submodule as a whole if no diagnostic
event is pending
In V3.0, the start information for an outgoing diagnostic error event always indicated the
source of the event. In V4.0, if the outgoing event leaves the submodule with no pending
diagnostics, the start information references the submodule as a whole (16#8000) even if the
source of the event was a specific channel.
For example, if a wire break triggers a diagnostic error event on channel 2, the fault is then
corrected, and the diagnostic error event is cleared, the Start information will not reference
channel 2, but the submodule (16#8000).

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Table 5- 7

Startup information for the diagnostic error interrupt OB

Input

Data type

Description

IOstate

WORD

IO state of the device:
•

Bit 0 = 1 if the configuration is correct, and = 0 if the configuration is no longer correct.

•

Bit 4 = 1 if an error is present (such as a wire break). (Bit 4 = 0 if
there is no error.)

•

Bit 5 = 1 if the configuration is not correct, and = 0 if the configuration is correct again.

•

Bit 7 = 1 if an I/O access error has occurred. Refer to LADDR for
the hardware identifier of the I/O with the access error. (Bit 6 = 0
if there is no error.)

LADDR

HW_ANY

Hardware identifier of the device or functional unit that reported the
error1

Channel

UINT

Channel number

MultiError

BOOL

TRUE if more than one error is present

The LADDR input contains the hardware identifier of the device or functional unit which returned
the error. The hardware identifier is assigned automatically when components are inserted in the
device or network view and appears in the Constants tab of PLC tags. A name is also assigned
automatically for the hardware identifier. These entries in the Constants tab of the PLC tags cannot be changed.

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5.1.3.8

Pull or plug of modules OB
The "Pull or plug of modules" OB executes when a configured and non-disabled distributed
I/O module or submodule (PROFIBUS, PROFINET, AS-i) generates an event related to
inserting or removing a module.

Pull or plug of modules event
The following conditions generate a pull of plug of modules event:
● Someone removes or inserts a configured module
● A configured module is not physically present in an expansion rack
● An incompatible module is in an expansion rack that does not correspond to the
configured module
● A compatible module for a configured module is in an expansion rack, but the
configuration does not allow substitutes
● A module or submodule has parameterization errors
If you have not programmed this OB, the CPU remains in RUN mode when any of these
conditions occur with a configured and non-disabled distributed I/O module.
Regardless of whether you have programmed this OB, the CPU changes to STOP mode
when any of these conditions occur with a module in the central rack.
Table 5- 8

Start information for pull or plug of modules OB

Input

Data type

Description

LADDR

HW_IO

Hardware identifier

Event_Class

Byte

16#38: module inserted
16#29: module removed

Fault_ID

Byte

Fault identifier

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5.1.3.9

Rack or station failure OB
The "Rack or station failure" OB executes when the CPU detects the failure or
communication loss of a distributed rack or station.

Rack or station failure event
The CPU generates a rack or station failure event when it detects one of the following:
● The failure of a DP master system or of a PROFINET IO system (in the case of either an
incoming or an outgoing event).
● The failure of a DP slave or of an IO device (in the case of either an incoming or an
outgoing event)
● Failure of some of the submodules of a PROFINET I-device
If you have not programmed this OB, the CPU remains in RUN mode when any of these
conditions occur.
Table 5- 9

Start information for rack or station failure OB

Input

Data type

Description

LADDR

HW_IO

Hardware identifier

Event_Class

Byte

16#32: Activation of a DP slave or an IO device
16#33: Deactivation of a DP slave or an IO device
16#38: outgoing event
16#39: incoming event

Fault_ID

Byte

Fault identifier

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5.1.3.10

Time of day OB
Time of day OBs execute based on configured clock time conditions. The CPU supports two
time of day OBs.

Time of day events
You can configure a time of day interrupt event to occur once on a specified date or time or
cyclically with one of the following cycles:
● Every minute: The interrupt occurs every minute.
● Hourly: The interrupt occurs every hour.
● Daily: The interrupt occurs every day at a specified time (hour and minute).
● Weekly: The interrupt occurs every week at a specified time on a specified day of the
week (for example, every Tuesday at 4:30 in the afternoon).
● Monthly: The interrupt occurs every month at a specified time on a specified day of the
month. The day number must be between 1 and 28, inclusive.
● Every end of month: The interrupt occurs on the last day of every month at a specified
time.
● Yearly: The interrupt occurs every year on the specified date (month and day). You
cannot specify a date of February 29.
Table 5- 10

Start information for a time of day event OB

Input

Data type

Description

CaughtUp

Bool

OB call is caught up because time was set forward

SecondTimes Bool

5.1.3.11

OB call is started a second time because time was set backward

Status OB
Status OBs execute if a DPV1 or PNIO slave triggers a status interrupt. This might be the
case if a component (module or rack) of a DPV1 or PNIO slave changes its operating mode,
for example from RUN to STOP.

Status events
For detailed information on events that trigger a status interrupt, refer to the manufacturer's
documentation for the DPV1 or PNIO slave.
Table 5- 11

Start information for status OB

Input

Data type

Description

LADDR

HW_IO

Hardware identifier

Slot

UInt

Slot number

Specifier

Word

Alarm specifier

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5.1.3.12

Update OB
Update OBs execute if a DPV1 or PNIO slave triggers an update interrupt.

Update events
For detailed information on events that trigger an update interrupt, refer to the manufacturer's
documentation for the DPV1 or PNIO slave.
Table 5- 12

5.1.3.13

Start information for update OB

Input

Data type

Description

LADDR

HW_IO

Hardware identifier

Slot

UInt

Slot number

Specifier

Word

Alarm specifier

Profile OB
Profile OBs execute if a DPV1 or PNIO slave triggers a profile-specific interrupt.

Profile events
For detailed information on events that trigger a profile interrupt, refer to the manufacturer's
documentation for the DPV1 or PNIO slave.
Table 5- 13

5.1.3.14

Start information for profile OB

Input

Data type

Description

LADDR

HW_IO

Hardware identifier

Slot

UInt

Slot number

Specifier

Word

Alarm specifier

MC-Servo and MC-Interpolator OB
STEP 7 creates the read-only MC-Servo and MC-Interpolator OBs automatically when you
create a motion technology object and set the drive interface to be "Analog drive connection"
or "PROFIDrive". You do not need to edit any OB properties or create this OB directly. The
CPU uses these OBs for closed loop control. Refer to the STEP 7 Information System for
further details.

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5.1.3.15

MC-PreServo
You can program the MC-PreServo OB to contain program logic for the STEP 7 program to
execute directly before the MC-Servo OB executes.

MC-PreServo events
The MC-PreServo OB allows you to read out the configured application cycle information in
microseconds.
Table 5- 14

Start information for MC-PreServo OB

Input

Data type

Description

Initial_Call

BOOL

TRUE indicates first call of this OB on transition from STOP to RUN

PIP_Input

BOOL

TRUE indicates the associated process image input is up to date.

PIP_Output

BOOL

TRUE indicates that the CPU transferred the associated process
image output to the outpus in good time after the last cycle.

IO_System

USINT

Number of the distributed I/O system triggering the interrupt

Event_Count

INT

n: number of lost cycles
-1: unknown number of cycles lost (for example, because cycle has
changed)

Synchronous

BOOL

Reserved

CycleTime

UDINT

Display of the application cycle configured for the MC-Servo OB in
microseconds

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5.1.3.16

MC-PostServo
You can program the MC-PreServo OB to contain program logic for the STEP 7 program to
execute directly after the MC-Servo OB executes.

MC-PostServo events
The MC-PreServo OB allows you to read out the configured application cycle information in
microseconds.
Table 5- 15

Start information for MC-PostServo OB

Input

Data type

Description

Initial_Call

BOOL

TRUE indicates first call of this OB on transition from STOP to RUN

PIP_Input

BOOL

TRUE indicates the associated process image input is up to date.

PIP_Output

BOOL

TRUE indicates that the CPU transferred the associated process
image output to the outpus in good time after the last cycle.

IO_System

USINT

Number of the distributed I/O system triggering the interrupt

Event_Count

INT

n: number of lost cycles
-1: unknown number of cycles lost (for example, because cycle has
changed)

5.1.3.17

Synchronous

BOOL

Reserved

CycleTime

UDINT

Display of the application cycle configured for the MC-Servo OB in
microseconds

Event execution priorities and queuing
The CPU processing is controlled by events. An event triggers an interrupt OB to be
executed. You can specify the interrupt OB for an event during the creation of the block,
during the device configuration, or with an ATTACH or DETACH instruction. Some events
happen on a regular basis like the program cycle or cyclic events. Other events happen only
a single time, like the startup event and time delay events. Some events happen when the
hardware triggers an event, such as an edge event on an input point or a high speed counter
event. Events like the diagnostic error and time error event only happen when an error
occurs. The event priorities and queues are used to determine the processing order for the
event interrupt OBs.
The CPU processes events in order of priority where 1 is the lowest priority and 26 is the
highest priority. Prior to V4.0 of the S7-1200 CPU, each type of OB belonged to a fixed
priority class (1 to 26). From V4.0 forward, you can assign a priority class to each OB that
you configure. You configure the priority number in the attributes of the OB properties.

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Interruptible and non-interruptible execution modes
OBs (Page 92) execute in priority order of the events that trigger them. In the Startup
properties of the device configuration of the CPU (Page 170), you can configure OB
execution to be interruptible or non-interruptible. Note that program cycle OBs are always
interruptible, but you can configure all other OBs to be either interruptible or noninterruptible.
If you set interruptible mode, then if an OB is executing and a higher priority event occurs
before the OB completes its execution, the running OB is interrupted to allow the higherpriority event OB to run. The higher-priority event runs, and at its completion, the OB that
was interrupted continues. When multiple events occur while an interruptible OB is
executing, the CPU processes those events in priority order.
If you do not set interruptible mode, then an OB runs to completion when triggered
regardless of any other events that trigger during the time that it is running.
Consider the following two cases where interrupt events trigger a cyclic OB and a time delay
OB. In both cases, the time delay OB (OB201) has no process image partition assignment
(Page 83) and executes at priority 4. The cyclic OB (OB200) has a process image partition
assignment of PIP1 and executes at priority 2. The following illustrations show the difference
in execution between non-interruptible and interruptible execution modes:

Figure 5-1

Case 1: Non-interruptible OB execution

Figure 5-2

Case 2: Interruptible OB execution

Note
If you configure the OB execution mode to be non-interruptible, then a time error OB cannot
interrupt OBs other than program cycle OBs. Prior to V4.0 of the S7-1200 CPU, a time error
OB could interrupt any executing OB. From V4.0 forward, you must configure OB execution
to be interruptible if you want a time error OB (or any other higher priority OB) to be able to
interrupt executing OBs that are not program cycle OBs.

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Understanding event execution priorities and queuing
The CPU limits the number of pending (queued) events from a single source, using a
different queue for each event type. Upon reaching the limit of pending events for a given
event type, the next event is lost. You can use a time error interrupt OB (Page 96) to
respond to queue overflows.
Note that STEP 7 allows you
to configure some specific
event queueing parameters
for the Cyclic interrupt OB
and the Time of day OB.

For further information on CPU overload behavior and event queueing, refer to the STEP 7
Information System.
Each CPU event has an associated priority. In general, the CPU services events in order of
priority (highest priority first). The CPU services events of the same priority on a "first-come,
first-served" basis.
Table 5- 16

OB events

Event

Quantity allowed

Program cycle

1 program cycle event

Default OB priority
14

Multiple OBs allowed
Startup

1 startup event 1

Multiple OBs allowed
Time delay

Up to 4 time events

1 OB per event
Cyclic interrupt

Up to 4 events

1 OB per event
Hardware interrupt

Up to 50 hardware interrupt events2

1 OB per event, but you can use the same OB for
multiple events

Time error

1 event (only if configured)3

22 or 264

Diagnostic error

1 event (only if configured)

Pull or plug of modules

1 event

Rack or station failure

1 event

Time of day

Up to 2 events

Status

1 event

Update

1 event

Profile

1 event

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Event

Quantity allowed

MC-Servo

1 event

Default OB priority
25

MC-Interpolator

1 event

The startup event and the program cycle event never occur at the same time because the startup
event runs to completion before the program cycle event starts.

You can have more than 50 hardware interrupt event OBs if you use the DETACH and ATTACH
instructions.

You can configure the CPU to stay in RUN if the scan cycle exceeds the maximum scan cycle time
or you can use the RE_TRIGR instruction to reset the cycle time. However, the CPU goes to
STOP mode the second time that one scan cycle exceeds the maximum scan cycle time.

The priority for a new V4.0 or V4.1 CPU is 22. If you exchange a V3.0 CPU for a V4.0 or V4.1
CPU, the priority is 26: the priority that was in effect for V3.0. In either case, the priority field is editable and you can set the priority to any value in the range 22 to 26.

Refer to the topic "Exchanging a V3.0 CPU for a V4.1 CPU (Page 1571)" for more details.
In addition, the CPU recognizes other events that do not have associated OBs. The following
table describes these events and the corresponding CPU actions:
Table 5- 17

Additional events

Event

Description

CPU action

I/O access error

Direct I/O read/write error

The CPU logs the first occurrence in the
diagnostic buffer and stays in RUN mode.
You can access the error cause using the
GET_ERROR_ID (Page 311) instruction.

Max cycle time error

CPU exceeds the configured
cycle time twice

The CPU logs the error in the diagnostic
buffer and transitions to STOP mode.

Peripheral access error

I/O error during process image update

The CPU logs the first occurrence in the
diagnostic buffer and stays in RUN mode.

Programming error

program execution error

•

If block-local error handling is enabled,
the system enters an error cause in the
error structure. You can access the error cause using the GET_ERROR_ID
(Page 311) instruction.

•

If global error handling is enabled, the
system enters an access error start
event into the diagnostic buffer and
stays in RUN mode.

Interrupt latency
The interrupt event latency (the time from notification of the CPU that an event has occurred
until the CPU begins execution of the first instruction in the OB that services the event) is
approximately 175 µsec, provided that a program cycle OB is the only event service routine
active at the time of the interrupt event.

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5.1.4

Monitoring and configuring the cycle time
The cycle time is the time that the CPU operating system requires to execute the cyclic
phase of the RUN mode. The CPU provides two methods of monitoring the cycle time:
● Maximum scan cycle time
● Minimum scan cycle time
Scan cycle monitoring begins after the startup event is complete. Configuration for this
feature appears under the "Device Configuration" for the CPU under "Cycle time".
The CPU always monitors the scan cycle and reacts if the maximum scan cycle time is
exceeded. If the configured maximum scan cycle time is exceeded, an error is generated
and is handled one of two ways:
● If the user program does not include a time error interrupt OB, then the timer error event
generates a diagnostic buffer entry, but the CPU remains in RUN mode. (You can change
the configuration of the CPU to go to STOP mode when it detects a time error, but the
default configuration is to remain in RUN mode.)
● If the user program includes a time error interrupt OB, then the CPU executes it.
The RE_TRIGR instruction (Page 309) (re-trigger cycle time monitoring) allows you to reset
the timer that measures the cycle time. If the elapsed time for the current program cycle
execution is less than ten times the configured maximum scan cycle time, the RE_TRIGR
instruction retriggers the cycle time monitoring and returns with ENO = TRUE. If not, the
RE_TRIGR instruction does not retrigger the cycle time monitoring. It returns ENO = FALSE.
Typically, the scan cycle executes as fast as it can be executed and the next scan cycle
begins as soon as the current one completes. Depending upon the user program and
communication tasks, the time period for a scan cycle can vary from scan to scan. To
eliminate this variation, the CPU supports an optional minimum scan cycle time. If you
enable this optional feature and provide a minimum scan cycle time in ms, then the CPU
delays after the execution of the program cycle OBs until the minimum scan cycle time
elapses before repeating the program cycle.
In the event that the CPU completes the normal scan cycle in less time than the specified
minimum cycle time, the CPU spends the additional time of the scan cycle performing
runtime diagnostics and/or processing communication requests.
In the event that the CPU does not complete the scan cycle in the specified minimum cycle
time, the CPU completes the scan normally (including communication processing) and does
not create any system reaction as a result of exceeding the minimum scan time. The
following table defines the ranges and defaults for the cycle time monitoring functions:
Table 5- 18

Range for the cycle time

Cycle time

Range (ms)

Default

Maximum scan cycle time1

1 to 6000

150 ms

1 to maximum scan cycle time

Disabled

Minimum scan cycle

time2

The maximum scan cycle time is always enabled. Configure a cycle time between 1 ms to 6000
ms. The default is 150 ms.

The minimum scan cycle time is optional, and is disabled by default. If required, configure a cycle
time between 1 ms and the maximum scan cycle time.

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Configuring the cycle time and communication load
You use the CPU properties in the Device configuration to configure the following
parameters:
● Cycle: You can enter a maximum scan cycle monitoring time. You can also enable and
enter a minimum scan cycle time.

● Communication load: You can configure a percentage of the time to be dedicated for
communication tasks.

For more information about the scan cycle, see "Monitoring the cycle time". (Page 109)

5.1.5

CPU memory

Memory management
The CPU provides the following memory areas to store the user program, data, and
configuration:
● Load memory is non-volatile storage for the user program, data and configuration. When
you download a project to the CPU, the CPU first stores the program in the Load memory
area. This area is located either in a memory card (if present) or in the CPU. The CPU
maintains this non-volatile memory area through a power loss. The memory card
supports a larger storage space than that built-in to the CPU.
● Work memory is volatile storage for some elements of the user project while executing
the user program. The CPU copies some elements of the project from load memory into
work memory. This volatile area is lost when power is removed, and is restored by the
CPU when power is restored.
● Retentive memory is non-volatile storage for a limited quantity of work memory values.
The CPU uses the retentive memory area to store the values of selected user memory
locations during power loss. When a power down or power loss occurs, the CPU restores
these retentive values upon power up.
To display the memory usage for a compiled program block, right-click the block in the
"Program blocks" folder in the STEP 7 project tree and select "Resources" from the context
menu. The Compiliation properties display the load memory and work memory for the
compiled block.
To display the memory usage for the online CPU, double-click "Online and diagnostics" in
STEP 7, expand "Diagnostics", and select "Memory".
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Retentive memory
You can avoid data loss after power failure by marking certain data as retentive. The CPU
allows you to configure the following data as retentive:
● Bit memory (M): You can define the size of retentive memory for bit memory in the PLC
tag table or in the assignment list. Retentive bit memory always starts at MB0 and runs
consecutively up through a specified number of bytes. Specify this value from the PLC
tag table or in the assignment list by clicking the "Retain" toolbar icon. Enter the number
of M bytes to retain starting at MB0.
Note: For any block, you can display the assignment list by selecting a block in the
Program Blocks folder and then selecting he Tools > Assignment list menu command.
● Tags of a function block (FB): If an FB is of type "Optimized block access", then the
interface editor for this FB includes a "Retain" column. In this column, you can select
either "Retain", "Non-retain", or "Set in IDB" individually for each tag. When you place
such an FB in the program, the instance DB that corresponds to the FB includes this
"Retain" column as well. You can only change the retentive state of a tag from within the
instance DB interface editor if you selected "Set in IDB" (Set in instance data block) in the
Retain selection for the tag in the optimized FB.
If an FB is not of type "Optimized block access", then the interface editor for this FB does
not include a "Retain" column. When you place such an FB in the program, the instance
DB that corresponds to the FB does, however, include a "Retain" column that is available
for edit. In this case, selecting the "Retain" option for any tag results in the selection of all
tags. Similarly, deselecting the option for any tag results in the deselection of all tags.
To view or modify whether an FB is optimized, open the properties of the FB and select
the attributes.
● Tags of a global data block: The behavior of a global DB with regard to retentive state
assignment is similar to that of an FB. Depending on the block access setting you can
define the retentive state either for individual tags or for all tags of a global data block.
– If you select "Optimized" when you create the DB, you can set the retentive state for
each individual tag.
– If you select "Standard - compatible with S7-300/400" when you create the DB, the
retentive-state setting applies to all tags of the DB; either all tags are retentive or no
tag is retentive.
The CPU supports a total of 10240 bytes of retentive data. To see how much is available,
from the PLC tag table or the assignment list, click the "Retain" toolbar icon. Although this is
where the retentive range is specified for M memory, the second row indicates the total
remaining memory available for M and DB combined. Note that for this value to be accurate,
you must compile all data blocks with retentive tags.
Note
Downloading a program does not clear or make any changes to existing values in retentive
memory. If you want to clear retentive memory before a download, then reset your CPU to
factory settings prior to downloading the program.

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5.1.5.1

System and clock memory
You use the CPU properties to enable bytes for "system memory" and "clock memory". Your
program logic can reference the individual bits of these functions by their tag names.
● You can assign one byte in M memory for system memory. The byte of system memory
provides the following four bits that can be referenced by your user program by the
following tag names:
– First cycle: (Tag name "FirstScan") bit is set to1 for the duration of the first scan after
the startup OB finishes. (After the execution of the first scan, the "first scan" bit is set
to 0.)
– Diagnostics status changed: (Tag name: "DiagStatusUpdate") is set to 1 for one scan
after the CPU logs a diagnostic event. Because the CPU does not set the
"DiagStatusUpdate" bit until the end of the first execution of the program cycle OBs,
your user program cannot detect if there has been a diagnostic change either during
the execution of the startup OBs or the first execution of the program cycle OBs.
– Always 1 (high): (Tag name "AlwaysTRUE") bit is always set to 1.
– Always 0 (low): (Tag name "AlwaysFALSE") bit is always set to 0.
● You can assign one byte in M memory for clock memory. Each bit of the byte configured
as clock memory generates a square wave pulse. The byte of clock memory provides 8
different frequencies, from 0.5 Hz (slow) to 10 Hz (fast). You can use these bits as control
bits, especially when combined with edge instructions, to trigger actions in the user
program on a cyclic basis.
The CPU initializes these bytes on the transition from STOP mode to STARTUP mode. The
bits of the clock memory change synchronously to the CPU clock throughout the STARTUP
and RUN modes.
CAUTION
Risks with overwriting the system memory or clock memory bits
Overwriting the system memory or clock memory bits can corrupt the data in these
functions and cause your user program to operate incorrectly, which can cause damage to
equipment and injury to personnel.
Because both the clock memory and system memory are unreserved in M memory,
instructions or communications can write to these locations and corrupt the data.
Avoid writing data to these locations to ensure the proper operation of these functions, and
always implement an emergency stop circuit for your process or machine.

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System memory configures a byte with bits that turn on (value = 1) for a specific event.

Table 5- 19
7

System memory
3

Reserved

Always off

Always on

First scan indicator

Value 0

Value 1

Diagnostic status indicator
•

1: Change

•

0: No change

•

1: First scan after
startup

•

0: Not first scan

Clock memory configures a byte that cycles the individual bits on and off at fixed intervals.
Each clock bit generates a square wave pulse on the corresponding M memory bit. These
bits can be used as control bits, especially when combined with edge instructions, to trigger
actions in the user code on a cyclic basis.

Table 5- 20

Clock memory

Bit number

Period (s)

2.0

1.6

1.0

0.8

0.5

0.4

0.2

0.1

Frequency (Hz)

0.5

0.625

1.25

2.5

Tag name

Because clock memory runs asynchronously to the CPU cycle, the status of the clock memory can
change several times during a long cycle.

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5.1.6

Diagnostics buffer
The CPU supports a diagnostics buffer that contains an entry for each diagnostic event.
Each entry includes a date and time the event occurred, an event category, and an event
description. The entries are displayed in chronological order with the most recent event at
the top. Up to 50 most recent events are available in this log. When the log is full, a new
event replaces the oldest event in the log. When power is lost, the events are saved.
The following types of events are recorded in the diagnostics buffer:
● Each system diagnostic event; for example, CPU errors and module errors
● Each state change of the CPU (each power up, each transition to STOP, each transition
to RUN)
To access the diagnostics buffer (Page 1322), you must be online. From the "Online &
diagnostics" view, locate the diagnostics buffer under "Diagnostics > Diagnostics buffer".

Reducing the number of security diagnostic events
Some security events generate repeated entries in the diagnostics buffer. These messages
can fill up the diagnostics buffer and potentially obscure other event messages. You can
configure the PLC to limit the number of diagnostic messages from security events. You
make selections in the device configuration of the CPU based on the time interval in which
you want to suppress recurring messages:

If you choose to summarize security events within a time interval, you have the choice of
setting a time interval in seconds, minutes, or hours, and a numerical value in the range 1 ..
255.
If you choose to restrict security events, you will be restricting these types of events:
● Going online with the correct or incorrect password
● Manipulated communications data detected
● Manipulated data detected on memory card
● Manipulated firmware update file detected
● Changed protection level (access protection) downloaded to the CPU
● Password legitimization restricted or enabled (by instruction or CPU display)
● Online access denied due to the possible number of simultaneous access attempts being
exceeded
● Timeout when an existing online connection is inactive
● Logging in to the Web server with the correct or incorrect password

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● Creating a backup of the CPU
● Restoring the CPU configuration

5.1.7

Time of day clock
The CPU supports a time-of-day clock. A super-capacitor supplies the energy required to
keep the clock running during times when the CPU is powered down. The super-capacitor
charges while the CPU has power. After the CPU has been powered up at least 24 hours,
then the super-capacitor has sufficient charge to keep the clock running for typically 20 days.
STEP 7 sets the time-of-day clock to system time, which has a default value out of the box or
following a factory reset. To utilize the time-of-day clock, you must set it. Timestamps such
as those for diagnostic buffer entries, data log files, and data log entries are based on the
system time. You set the time of day from the "Set time of day" function (Page 1316) in the
"Online & diagnostics" view of the online CPU. STEP 7 then calculates the system time from
the time you set plus or minus the Windows operating system offset from UTC (Coordinated
Universal Time). Setting the time of day to the current local time produces a system time of
UTC if your Windows operating system settings for time zone and daylight savings time
correspond to your locale.
STEP 7 includes instructions (Page 338) to read and write the system time (RD_SYS_T and
WR_SYS_T), to read the local time (RD_LOC_T), and to set the time zone
(SET_TIMEZONE). The RD_LOC_T instruction calculates local time using the time zone and
daylight saving time offsets that you set in the "Time of day" configuration in the general
properties of the CPU (Page 170). These settings enable you to set your time zone for local
time, optionally enable daylight saving time, and specify the start and end dates and times
for daylight saving time. You can also use the SET_TIMEZONE instructions to configure
these settings.

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5.1.8

Configuring the outputs on a RUN-to-STOP transition
You can configure the behavior of the digital and analog outputs when the CPU is in STOP
mode. For any output of a CPU, SB or SM, you can set the outputs to either freeze the value
or use a substitute value:
● Substituting a specified output value (default): You enter a substitute value for each
output (channel) of that CPU, SB, or SM device.
The default substitute value for digital output channels is OFF, and the default substitute
value for analog output channels is 0.
● Freezing the outputs to remain in last state: The outputs retain their current value at the
time of the transition from RUN to STOP. After power up, the outputs are set to the
default substitute value.
You configure the behavior of the outputs in Device Configuration. Select the individual
devices and use the "Properties" tab to configure the outputs for each device.
Note
Some distibuted I/O modules offer additional settings for the reaction to CPU stop mode.
Select from the list of choices in Device Configuration for those modules.
When the CPU changes from RUN to STOP, the CPU retains the process image and writes
the appropriate values for both the digital and analog outputs, based upon the configuration.

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5.2

Data storage, memory areas, I/O and addressing

5.2.1

Accessing the data of the S7-1200
STEP 7 facilitates symbolic programming. You create symbolic names or "tags" for the
addresses of the data, whether as PLC tags relating to memory addresses and I/O points or
as local variables used within a code block. To use these tags in your user program, simply
enter the tag name for the instruction parameter.
For a better understanding of how the CPU structures and addresses the memory areas, the
following paragraphs explain the "absolute" addressing that is referenced by the PLC tags.
The CPU provides several options for storing data during the execution of the user program:
● Global memory: The CPU provides a variety of specialized memory areas, including
inputs (I), outputs (Q) and bit memory (M). This memory is accessible by all code blocks
without restriction.
● PLC tag table: You can enter symbolic names in the STEP 7 PLC tag table for specific
memory locations. These tags are global to the STEP 7 program and allow programming
with names that are meaningful for your application.
● Data block (DB): You can include DBs in your user program to store data for the code
blocks. The data stored persists when the execution of the associated code block comes
to an end. A "global" DB stores data that can be used by all code blocks, while an
instance DB stores data for a specific FB and is structured by the parameters for the FB.
● Temp memory: Whenever a code block is called, the operating system of the CPU
allocates the temporary, or local, memory (L) to be used during the execution of the
block. When the execution of the code block finishes, the CPU reallocates the local
memory for the execution of other code blocks.

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Each different memory location has a unique address. Your user program uses these
addresses to access the information in the memory location. References to the input (I) or
output (Q) memory areas, such as I0.3 or Q1.7, access the process image. To immediately
access the physical input or output, append the reference with ":P" (such as I0.3:P, Q1.7:P,
or "Stop:P").
Table 5- 21

Memory areas

Memory area

Description

Force

Retentive

I
Process image input

Copied from physical inputs at the beginning of
the scan cycle

I_:P 1
(Physical input)

Immediate read of the physical input points on
the CPU, SB, and SM

Yes

Q
Process image output

Copied to physical outputs at the beginning of
the scan cycle

Q_:P 1
(Physical output)

Immediate write to the physical output points
on the CPU, SB, and SM

Yes

M
Bit memory

Control and data memory

Yes
(optional)

L
Temp memory

Temporary data for a block local to that block

DB
Data block

Data memory and also parameter memory for
FBs

Yes
(optional)

To immediately access (read or write) the physical inputs and physical outputs, append a ":P" to
the address or tag (such as I0.3:P, Q1.7:P, or "Stop:P").

Each different memory location has a unique address. Your user program uses these
addresses to access the information in the memory location. The absolute address consists
of the following elements:
● Memory area identifier (such as I, Q, or M)
● Size of the data to be accessed ("B' for Byte, "W" for Word, or "D" for DWord)
● Starting address of the data (such as byte 3 or word 3)

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When accessing a bit in the address for a Boolean value, you do not enter a mnemonic for
the size. You enter only the memory area, the byte location, and the bit location for the data
(such as I0.0, Q0.1, or M3.4).

Memory area identifier

Bytes of the memory area

Byte address: byte 3

Bits of the selected byte

Separator ("byte.bit")

Bit location of the byte (bit 4 of 8)

In the example, the memory area and byte address (M = bit memory area, and 3 = Byte 3)
are followed by a period (".") to separate the bit address (bit 4).

Accessing the data in the memory areas of the CPU
STEP 7 facilitates symbolic programming. Typically, you create tags either in the PLC tag
table, a data block, or in the interface of an OB, FC, or FB. These tags include a name, data
type, offset, and comment. Additionally, in a data block, you can specify a start value. You
can use these tags when programming by entering the tag name at the instruction
parameter. Optionally you can enter the absolute operand (memory area, size and offset) at
the instruction parameter. The examples in the following sections show how to enter
absolute operands. The % character is inserted automatically in front of the absolute
operand by the program editor. You can toggle the view in the program editor to one of
these: symbolic, symbolic and absolute, or absolute.
I (process image input): The CPU samples the peripheral (physical) input points just prior to
the cyclic OB execution of each scan cycle and writes these values to the input process
image. You can access the input process image as bits, bytes, words, or double words. Both
read and write access is permitted, but typically, process image inputs are only read.
Table 5- 22

Absolute addressing for I memory

Bit

I[byte address].[bit address]

I0.1

Byte, Word, or Double Word

I[size][starting byte address]

IB4, IW5, or ID12

By appending a ":P" to the address, you can immediately read the digital and analog inputs
of the CPU, SB, SM or distributed module. The difference between an access using I_:P
instead of I is that the data comes directly from the points being accessed rather than from
the input process image. This I_:P access is referred to as an "immediate read" access
because the data is retrieved immediately from the source instead of from a copy that was
made the last time the input process image was updated.
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Because the physical input points receive their values directly from the field devices
connected to these points, writing to these points is prohibited. That is, I_:P accesses are
read-only, as opposed to I accesses which can be read or write.
I_:P accesses are also restricted to the size of inputs supported by a single CPU, SB, or SM,
rounded up to the nearest byte. For example, if the inputs of a 2 DI / 2 DQ SB are configured
to start at I4.0, then the input points can be accessed as I4.0:P and I4.1:P or as IB4:P.
Accesses to I4.2:P through I4.7:P are not rejected, but make no sense since these points are
not used. Accesses to IW4:P and ID4:P are prohibited since they exceed the byte offset
associated with the SB.
Accesses using I_:P do not affect the corresponding value stored in the input process image.
Table 5- 23

Absolute addressing for I memory (immediate)

Bit

I[byte address].[bit address]:P

I0.1:P

Byte, Word, or Double word

I[size][starting byte address]:P

IB4:P, IW5:P, or ID12:P

Q (process image output): The CPU copies the values stored in the output process image to
the physical output points. You can access the output process image in bits, bytes, words, or
double words. Both read and write access is permitted for process image outputs.
Table 5- 24

Absolute addressing for Q memory

Bit

Q[byte address].[bit address]

Q1.1

Byte, Word, or Double word

Q[size][starting byte address]

QB5, QW10, QD40

By appending a ":P" to the address, you can immediately write to the physical digital and
analog outputs of the CPU, SB, SM or distributed module. The difference between an access
using Q_:P instead of Q is that the data goes directly to the points being accessed in addition
to the output process image (writes to both places). This Q_:P access is sometimes referred
to as an "immediate write" access because the data is sent immediately to the target point;
the target point does not have to wait for the next update from the output process image.
Because the physical output points directly control field devices that are connected to these
points, reading from these points is prohibited. That is, Q_:P accesses are write-only, as
opposed to Q accesses which can be read or write.
Q_:P accesses are also restricted to the size of outputs supported by a single CPU, SB, or
SM, rounded up to the nearest byte. For example, if the outputs of a 2 DI / 2 DQ SB are
configured to start at Q4.0, then the output points can be accessed as Q4.0:P and Q4.1:P or
as QB4:P. Accesses to Q4.2:P through Q4.7:P are not rejected, but make no sense since
these points are not used. Accesses to QW4:P and QD4:P are prohibited since they exceed
the byte offset associated with the SB.
Accesses using Q_:P affect both the physical output as well as the corresponding value
stored in the output process image.
Table 5- 25

Absolute addressing for Q memory (immediate)

Bit

Q[byte address].[bit address]:P

Q1.1:P

Byte, Word, or Double word

Q[size][starting byte address]:P

QB5:P, QW10:P or QD40:P

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M (bit memory area): Use the bit memory area (M memory) for both control relays and data
to store the intermediate status of an operation or other control information. You can access
the bit memory area in bits, bytes, words, or double words. Both read and write access is
permitted for M memory.
Table 5- 26

Absolute addressing for M memory

Bit

M[byte address].[bit address]

M26.7

Byte, Word, or Double Word

M[size][starting byte address]

MB20, MW30, MD50

Temp (temporary memory): The CPU allocates the temp memory on an as-needed basis.
The CPU allocates the temp memory for the code block and initializes the memory locations
to 0 at the time when it starts the code block (for an OB) or calls the code block (for an FC or
FB).
Temp memory is similar to M memory with one major exception: M memory has a "global"
scope, and temp memory has a "local" scope:
● M memory: Any OB, FC, or FB can access the data in M memory, meaning that the data
is available globally for all of the elements of the user program.
● Temp memory: The CPU restricts access to the data in temp memory to the OB, FC, or
FB that created or declared the temp memory location. Temp memory locations remain
local and different code blocks do not share temp memory, even when the code block
calls another code block. For example: When an OB calls an FC, the FC cannot access
the temp memory of the OB that called it.
The CPU provides temp (local) memory for each OB priority level:
● 16 Kbytes for startup and program cycle, including associated FBs and FCs
● 6 Kbytes for each additional interrupt event thread, including associated FBs and FCs
You access temp memory by symbolic addressing only.
You can find out the amount of temp (local) memory that the blocks in your program use
through the call structure in STEP 7. From the project tree select Program info and then
select the Call structure tab. You will see all of the OBs in your program and you can drill
down to see the blocks that they call. For each block, you can see the local data allocation.
You can also access the Call structure display from the STEP 7 Tools > Call structure menu
command.
DB (data block): Use the DB memory for storing various types of data, including intermediate
status of an operation or other control information parameters for FBs, and data structures
required for many instructions such as timers and counters. You can access data block
memory in bits, bytes, words, or double words. Both read and write access is permitted for
read/write data blocks. Only read access is permitted for read-only data blocks.
Table 5- 27

Absolute addressing for DB memory

Bit

DB[data block number].DBX[byte address].[bit address]

DB1.DBX2.3

Byte, Word, or Double
Word

DB[data block number].DB [size][starting
byte address]

DB1.DBB4, DB10.DBW2,
DB20.DBD8

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Note
When you specify an absolute address in LAD or FBD, STEP 7 precedes this address with a
"%" character to indicate that it is an absolute address. While programming, you can enter
an absolute address either with or without the "%" character (for example %I0.0 or I.0). If
omitted, STEP 7 supplies the "%" character.
In SCL, you must enter the "%" before the address to indicate that it is an absolute address.
Without the "%", STEP 7 generates an undefined tag error at compile time

Configuring the I/O in the CPU and I/O modules
When you add a CPU and I/O modules to your
device configuration, STEP 7 automatically assigns
I and Q addresses. You can change the default
addressing by selecting the address field in the
device configuration and entering new numbers.
• STEP 7 assigns digital inputs and outputs in
groups of 8 points (1 byte), whether the module
uses all the points or not.
• STEP 7 allocates analog inputs and outputs in
groups of 2, where each analog poing occupies
2 bytes (16 bits).

The figure shows an example of a CPU 1214C with two SMs and one SB. In this example,
you could change the address of the DI8 module to 2 instead of 8. The tool assists you by
changing address ranges that are the wrong size or conflict with other addresses.

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5.3

Processing of analog values
Analog signal modules provide input signals or expect output values that represent either a
voltage range or a current range. These ranges are ±10 V, ±5 V, ±2.5 V, or 0 - 20 mA. The
values returned by the modules are integer values where 0 to 27648 represents the rated
range for current, and -27648 to 27648 for voltage. Anything outside the range represents
either an overflow or underflow. See the tables for analog input representation (Page 1471)
and analog output representation (Page 1472) for details about the types of out-of-range
values.
In your control program, you probably need to use these values in engineering units, for
example to represent a volume, temperature, weight or other quantitative value. To do this
for an analog input, you must first normalize the analog value to a real (floating point) value
from 0.0 to 1.0. Then you must scale it to the minimum and maximum values of the
engineering units that it represents. For values that are in engineering units that you need to
convert to an analog output value, you first normalize the value in engineering units to a
value between 0.0 and 1.0, and then scale it between 0 and 27648 or -27648 to 27648,
depending on the range of the analog module. STEP 7 provides the NORM_X and SCALE_X
instructions (Page 296) for this purpose. You can also use the CALCULATE instruction
(Page 255) to scale the analog values (Page 42).

Example: analog value processing
Consider, for example, an analog input that has a current range of 0 - 20 mA. The analog
input module returns values in the range 0 to 24768 for measured values. For this example,
consider that you are using this analog input value to measure a temperature range from
50 °C to 100 °C. A few sample values would have the following meanings:
Analog input value

Engineering units

50 °C

6192

62.5 °C

12384

75 °C

18576

87.5 °C

24768

100 °C

The calculation for determining engineering units from the analog input value in this example
is as follows:
Engineering units value = 50 + (Analog input value) * (100 - 50) / (24768 - 0)
For the general case, the equation would be:
Englineering units value = (Low range of engineering units) +
(Analog input value) *
(High range of engineering units - Low range of engineering units) /
(Maximum analog input range - Minimum analog input range)

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In PLC applications, the typical method is to normalize the analog input value to a floating
point value between 0.0 and 1.0. Then, you would scale the resulting value to a floating point
value in the range of your engineering units. For simplicity, the following LAD instructions
use constant values for the ranges; you might actually choose to use tags:
Network 1

Network 2

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5.4

Data types
Data types are used to specify both the size of a data element as well as how the data are to
be interpreted. Each instruction parameter supports at least one data type, and some
parameters support multiple data types. Hold the cursor over the parameter field of an
instruction to see which data types are supported for a given parameter.
A formal parameter is the identifier on an instruction that marks the location of data to be
used by that instruction (example: the IN1 input of an ADD instruction). An actual parameter
is the memory location (preceded by a "%" character) or constant containing the data to be
used by the instruction (example %MD400 "Number_of_Widgets"). The data type of the
actual parameter specified by you must match one of the supported data types of the formal
parameter specified by the instruction.
When specifying an actual parameter, you must specify either a tag (symbol) or an absolute
(direct) memory address. Tags associate a symbolic name (tag name) with a data type,
memory area, memory offset, and comment, and can be created either in the PLC tags
editor or in the Interface editor for a block (OB, FC, FB and DB). If you enter an absolute
address that has no associated tag, you must use an appropriate size that matches a
supported data type, and a default tag will be created upon entry.
All data types except String, Struct, Array, and DTL are available in the PLC tags editor and
the block Interface editors. String, Struct, Array, and DTL are available only in the block
Interface editors. You can also enter a constant value for many of the input parameters.
● Bit and Bit sequences (Page 126): Bool (Boolean or bit value), Byte (8-bit byte value),
Word (16-bit value), DWord (32-bit double word value)
● Integer (Page 127)
– USInt (unsigned 8-bit integer), SInt (signed 8-bit integer),
– UInt (unsigned 16-bit integer), Int (signed 16-bit integer)
– UDInt (unsigned 32-bit integer), DInt (signed 32-bit integer)
● Floating-point Real (Page 127): Real (32-bit Real or floating-point value), LReal (64-bit
Real or floating-point value)
● Time and Date (Page 128): Time (32-bit IEC time value), Date (16-bit date value), TOD
(32-bit time-of-day value), DTL (12-byte date-and-time structure)
● Character and String (Page 130): Char (8-bit single character), String (variable-length
string of up to 254 characters)
● Array (Page 132)
● Data structure (Page 133): Struct
● PLC data type (Page 133)
● Variant data type (Page 134)

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Although not available as data types, the following BCD numeric format is supported by the
conversion instructions:
Table 5- 28

5.4.1

Size and range of the BCD format

Format

Size (bits)

Numeric Range

Constant Entry Examples

BCD16

-999 to 999

123, -123

BCD32

-9999999 to 9999999

1234567, -1234567

Bool, Byte, Word, and DWord data types

Table 5- 29

Bit and bit sequence data types

Data
type

Bit
size

Number
type

Number
range

Constant
examples

Address
examples

Bool

Boolean

FALSE or TRUE

TRUE

I1.0
Q0.1
M50.7
DB1.DBX2.3
Tag_name

Byte

Word

Binary

2#0 or 2#1

2#0

Unsigned integer

0 or 1

Octal

8#0 or 8#1

8#1

Hexadecimal

16#0 or 16#1

16#1

Binary

2#0 to 2#1111_1111

2#1000_1001

Unsigned integer

0 to 255

Signed integer

-128 to 127

-63

Octal

8#0 to 8#377

8#17

Hexadecimal

B#16#0 to B#16#FF, 16#0 to
16#FF

B#16#F, 16#F

Binary
Signed integer

2#0 to 2#1111_1111_1111_1111 2#1101_0010_1001_0110 MW10
DB1.DBW2
0 to 65535
61680
Tag_name
-32768 to 32767
72

Octal

8#0 to 8#177_777

8#170_362

Hexadecimal

W#16#0 to W#16#FFFF,

W#16#F1C0, 16#A67B

Unsigned integer

IB2
MB10
DB1.DBB4
Tag_name

16#0 to 16#FFFF
DWord

Binary

2#0 to
2#1111_1111_1111_1111_1111
_1111_1111_1111

2#1101_0100_1111_1110 MD10
_1000_1100
DB1.DBD8
Tag_name

Unsigned integer*

0 to 4_294_967_295

15_793_935

Signed integer*

-2_147_483_648 to
2_147_483_647

-400000

Octal

8#0 to 8#37_777_777_777

8#74_177_417

Hexadecimal

DW#16#0000_0000 to
DW#16#FFFF_FFFF,

DW#16#20_F30A,
16#B_01F6

16#0000_0000 to
16#FFFF_FFFF
* The underscore "_" is a thousands separator to enhance readability for numbers greater than eight digits.

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5.4.2

Integer data types
Table 5- 30
Data
type

5.4.3

Integer data types (U = unsigned, S = short, D= double)

Bit size Number Range

Constant examples

Address
examples

USInt

0 to 255

78, 2#01001110

SInt

-128 to 127

+50, 16#50

UInt

0 to 65,535

65295, 0

Int

-32,768 to 32,767

30000, +30000

UDInt

0 to 4,294,967,295

4042322160

DInt

-2,147,483,648 to 2,147,483,647

-2131754992

MB0, DB1.DBB4,
Tag_name
MW2, DB1.DBW2,
Tag_name
MD6, DB1.DBD8,
Tag_name

Floating-point real data types
Real (or floating-point) numbers are represented as 32-bit single-precision numbers (Real),
or 64-bit double-precision numbers (LReal) as described in the ANSI/IEEE 754-1985
standard. Single-precision floating-point numbers are accurate up to 6 significant digits and
double-precision floating point numbers are accurate up to 15 significant digits. You can
specify a maximum of 6 significant digits (Real) or 15 (LReal) when entering a floating-point
constant to maintain precision.
Table 5- 31

Floating-point real data types (L=Long)

Data
type

Bit size Number range

Constant Examples

Real

-3.402823e+38 to -1.175 495e-38, 123.456, -3.4, 1.0e-5
±0,
+1.175 495e-38 to
+3.402823e+38

MD100,
DB1.DBD8,
Tag_name

LReal

-1.7976931348623158e+308 to
-2.2250738585072014e-308,
±0,
+2.2250738585072014e-308 to
+1.7976931348623158e+308

DB_name.var_nam
e

12345.123456789e40,
1.2E+40

Address examples

Rules:
•

No direct addressing support

•

Can be assigned in an
OB, FB, or FC
block interface
table

Calculations that involve a long series of values including very large and very small numbers
can produce inaccurate results. This can occur if the numbers differ by 10 to the power of x,
where x > 6 (Real), or 15 (LReal). For example (Real): 100 000 000 + 1 = 100 000 000.

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5.4.4

Time and Date data types
Table 5- 32

Time and date data types

Data type

Size

Range

Constant Entry Examples

Time

32 bits

T#-24d_20h_31m_23s_648ms to
T#24d_20h_31m_23s_647ms

T#5m_30s
T#1d_2h_15m_30s_45ms
TIME#10d20h30m20s630ms
500h10000ms
10d20h30m20s630ms

Stored as: -2,147,483,648 ms to
+2,147,483,647 ms
Date

16 bits

D#1990-1-1 to D#2168-12-31

D#2009-12-31
DATE#2009-12-31
2009-12-31

Time_of_Day 32 bits

TOD#0:0:0.0 to TOD#23:59:59.999

TOD#10:20:30.400
TIME_OF_DAY#10:20:30.400
23:10:1

DTL
(Date and
Time Long)

Min.: DTL#1970-01-01-00:00:00.0
Max.: DTL#2262-04-11:23:47:16.854 775
807

DTL#2008-12-1620:30:20.250

12
bytes

Time
TIME data is stored as a signed double integer interpreted as milliseconds. The editor format
can use information for day (d), hours (h), minutes (m), seconds (s) and milliseconds (ms).
It is not necessary to specify all units of time. For example T#5h10s and 500h are valid.
The combined value of all specified unit values cannot exceed the upper or lower limits in
milliseconds for the Time data type (-2,147,483,648 ms to +2,147,483,647 ms).

Date
DATE data is stored as an unsigned integer value which is interpreted as the number of days
added to the base date 01/01/1990, to obtain the specified date. The editor format must
specify a year, month and day.

TOD
TOD (TIME_OF_DAY) data is stored as an unsigned double integer which is interpreted as
the number of milliseconds since midnight for the specified time of day (Midnight = 0 ms).
The hour (24hr/day), minute, and second must be specified. The fractional second
specification is optional.

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DTL
DTL (Date and Time Long) data type uses a12 byte structure that saves information on date
and time. You can define DTL data in either the Temp memory of a block or in a DB. A value
for all components must be entered in the "Start value" column of the DB editor.
Table 5- 33

Size and range for DTL

Length
(bytes)

Format

Value range

Example of value
input

Clock and calendar

Min.: DTL#1970-01-01-00:00:00.0

DTL#2008-12-1620:30:20.250

Year-MonthMax.: DTL#2554-12-31-23:59:59.999 999
Day:Hour:Minute:
999
Second.Nanoseconds

Each component of the DTL contains a different data type and range of values. The data
type of a specified value must match the data type of the corresponding components.
Table 5- 34

Elements of the DTL structure

Byte

Component

Data type

Value range

Year

UINT

1970 to 2554

Month

USINT

1 to 12

Day

USINT

1 to 31

Weekday 1

USINT

1(Sunday) to 7(Saturday) 1

Hour

USINT

0 to 23

Minute

USINT

0 to 59

Second

USINT

0 to 59

Nanoseconds

UDINT

0 to 999 999 999

9
10
11
1

The format Year-Month-Day:Hour:Minute:
Second.Nanosecond does not include the weekday.

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5.4.5

Character and String data types
Table 5- 35

Character and String data types

Data type

Size

Range

Constant Entry Examples

Char

8 bits

16#00 to 16#FF

'A', 't', '@', 'ä', '∑'

WChar

16 bits

16#0000 to 16#FFFF

'A', 't', '@', 'ä', '∑', Asian characters, Cyrillic
characters, and others

String

n+ 2 bytes

n = (0 to 254 bytes)

"ABC"

WString

n+ 2 words

n = (0 to 65534 words)

"ä123@XYZ.COM"

Char and WChar
A Char occupies one byte in memory and stores a single character coded in ASCII format,
including the extended ASCII character codes. A WChar occupies one word in memory and
can contain any double-byte character representation.
The editor syntax uses a single quote character before and after the character. You can use
visible characters and control characters.

String and WString
The CPU supports the String data type for storing a sequence of single-byte characters. The
String data type contains a total character count (number of characters in the string) and the
current character count. The String type provides up to 256 bytes for storing the maximum
total character count (1 byte), the current character count (1 byte), and up to 254 bytes in the
string. Each byte in a String data type can be any value from 16#00 - 16#FF.
The WString data type provides for longer strings of one-word (double-byte) values. The first
word contains the maximum total character count; the next word contains the total character
count, and the following string can contain up to 65534 words. Each word in a WString data
type can be any value from 16#0000 - 16#FFFF.
You can use literal strings (constants) for instruction parameters of type IN using single
quotes. For example, ‘ABC’ is a three-character string that could be used as input for
parameter IN of the S_CONV instruction. You can also create string variables by selecting
data type "String" or "WString" in the block interface editors for OB, FC, FB, and DB. You
cannot create a string in the PLC tags editor.
You can specify the maximum string size in bytes (String) or words (WString) by entering
square brackets after the keyword "String" or "WString" after you select one of those data
types from the data type drop-down list. For example, "MyString String[10]" would specify a
10-byte maximum size for MyString. If you do not include the square brackets with a
maximum size, then 254 is assumed for a string and 65534 for a WString. "MyWString
WString[1000]" would specify a 1000-word WString.

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The following example defines a String with maximum character count of 10 and current
character count of 3. This means the String currently contains 3 one-byte characters, but
could be expanded to contain up to 10 one-byte characters.
Table 5- 36

Example of a String data type

Total Character Count

Current Character Count

Character 1

Character 2

Character 3

...

Character 10

'C' (16#43)

'A' (16#41)

'T' (16#54)

...

Byte 0

Byte 1

Byte 2

Byte 3

Byte 4

...

Byte 11

The following example defines a WString with maximum character count of 500 and current
character count of 300. This means the String currently contains 300 one-word characters,
but could be expanded to contain up to 500 one-word characters.
Table 5- 37

Example of a WString data type

Total Character Count

Current Character Count

Character 1

500

300

'ä' (16#0084)

Word 0

Word 1

Word 2

Characters
2 to 299

Character
300

ASCII charac- 'M' (16#004D)
ter words
Words 3 to
300

Word 301

...

Character 500

...

Word 501

ASCII control characters can be used in Char, Wchar, String and WString data. The
following table shows examples of control character syntax.
Table 5- 38

Valid ASCII control characters

Control characters

ASCII Hex
value (Char)

ASCII Hex
value (WChar)

Control function

Examples

$L or $l

16#0A

16#000A

Line feed

'$LText', '$0AText'

$N or $n

16#0A and
16#0D

16#000A and
16#000D

Line break

'$NText',
'$0A$0DText'

$P or $p

16#0C

16#000C

Form feed

'$PText', '$0CText'

$R or $r

16#0D

16#000D

Carriage return (CR)

'$RText','$0DText'

$T or $t

16#09

16#0009

Tab

'$TText', '$09Text'

16#24

16#0024

Dollar sign

'100$$', '100$24'

16#27

16#0027

Single quote

'$'Text$'','$27Text$
27'

The new line shows two
characters in the string.

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5.4.6

Array data type

Arrays
You can create an array that contains multiple elements of the same data type. Arrays can
be created in the block interface editors for OB, FC, FB, and DB. You cannot create an array
in the PLC tags editor.
To create an array from the block interface editor, name the array and choose data type
"Array [lo .. hi] of type", then edit "lo", "hi", and "type" as follows:
● lo - the starting (lowest) index for your array
● hi - the ending (highest) index for your array
● type - one of the data types, such as BOOL, SINT, UDINT
Table 5- 39

ARRAY data type rules

Data Type

Array syntax

ARRAY

Name [index1_min..index1_max, index2_min..index2_max] of
•

All array elements must be the same data type.

•

The index can be negative, but the lower limit must be less than or equal to the upper limit.

•

Arrays can have one to six dimensions.

•

Multi-dimensional index min..max declarations are separated by comma characters.

•

Nested arrays, or arrays of arrays, are not allowed.

•

The memory size of an array = (size of one element * total number of elements in array)

Array index

Valid index data types

Array index rules

Constant or variable

USInt, SInt, UInt, Int, UDInt,
DInt

•

Value limits: -32768 to +32767

•

Valid: Mixed constants and variables

•

Valid: Constant expressions

•

Not valid: Variable expressions

Example: array
declarations
Example: array
addresses

ARRAY[1..20] of REAL

One dimension, 20 elements

ARRAY[-5..5] of INT

One dimension, 11 elements

ARRAY[1..2, 3..4] of CHAR

Two dimensions, 4 elements

ARRAY1[0]

ARRAY1 element 0

ARRAY2[1,2]

ARRAY2 element [1,2]

ARRAY3[i,j]

If i =3 and j=4, then ARRAY3 element
[3, 4] is addressed

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5.4.7

Data structure data type
You can use the data type "Struct" to define a structure of data consisting of other data
types. The struct data type can be used to handle a group of related process data as a single
data unit. A Struct data type is named and the internal data structure declared in the data
block editor or a block interface editor.
Arrays and structures can also be assembled into a larger structure. A structure can be
nested up to eight levels deep. For example, you can create a structure of structures that
contain arrays.

5.4.8

PLC data type
The PLC data type editor lets you define data structures that you can use multiple times in
your program. You create a PLC data type by opening the "PLC data types" branch of the
project tree and double-clicking the "Add new data type" item. On the newly created PLC
data type item, use two single-clicks to rename the default name and double-click to open
the PLC data type editor.
You create a custom PLC data type structure using the same editing methods that are used
in the data block editor. Add new rows for any data types that are necessary to create the
data structure that you want.
If a new PLC data type is created, then the new PLC type name will appear in the data type
selector drop-down lists in the DB editor and code block interface editor.
You can potentially use PLC data types in the following ways:
● As a data type in a code block interface or in data blocks
● As a template for the creation of multiple global data blocks that use the same data
structure
● As a data type for PLC tag declarations the I and Q memory areas of the CPU
For example, a PLC data type could be a recipe for mixing colors. You can then assign this
PLC data type to multiple data blocks. You can adjust the variables within each data block to
create a specific color.

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5.4.9

Variant pointer data type
The data type Variant can point to variables of different data types or parameters. The
Variant pointer can point to structures and individual structural components. The Variant
pointer does not occupy any space in memory.
Table 5- 40

Properties of the Variant pointer

Length
(Byte)

Representation

Format

Example entry

Symbolic

Operand

MyTag

DB_name.Struct_name.element_name

MyDB.Struct1.pressure1

Operand

%MW10

DB_number.Operand Type Length

P#DB10.DBX10.0 INT 12

Absolute

5.4.10

Accessing a "slice" of a tagged data type
PLC tags and data block tags can be accessed at the bit, byte, or word level depending on
their size. The syntax for accessing such a data slice is as follows:
● "".xn (bit access)
● "".bn (byte access)
● "".wn (word access)
● ""..xn (bit access)
● ""..bn (byte access)
● ""..wn (word access)
A double word-sized tag can be accessed by bits 0 - 31, bytes 0 - 3, or word 0 - 1. A wordsized tag can be accessed by bits 0 - 15, bytes 0 - 1, or word 0. A byte-sized tag can be
accessed by bits 0 - 7, or byte 0. Bit, byte, and word slices can be used anywhere that bits,
bytes, or words are expected operands.

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Note
Valid data types that can be accessed by slice are Byte, Char, Conn_Any, Date, DInt,
DWord, Event_Any, Event_Att, Hw_Any, Hw_Device, HW_Interface, Hw_Io, Hw_Pwm,
Hw_SubModule, Int, OB_Any, OB_Att, OB_Cyclic, OB_Delay, OB_WHINT, OB_PCYCLE,
OB_STARTUP, OB_TIMEERROR, OB_Tod, Port, Rtm, SInt, Time, Time_Of_Day, UDInt,
UInt, USInt, and Word. PLC Tags of type Real can be accessed by slice, but data block tags
of type Real cannot.

Examples
In the PLC tag table, "DW" is a declared tag of type DWORD. The examples show bit, byte,
and word slice access:
LAD

FBD

Bit access

SCL
IF "DW".x11 THEN
...
END_IF;

Byte access

IF "DW".b2 = "DW".b3
THEN
...
END_IF;

Word access

out:= "DW".w0 AND
"DW".w1;

5.4.11

Accessing a tag with an AT overlay
The AT tag overlay allows you to access an already-declared tag of a standard access block
with an overlaid declaration of a different data type. You can, for example, address the
individual bits of a tag of a Byte, Word, or DWord data type with an Array of Bool.

Declaration
To overlay a parameter, declare an additional parameter directly after the parameter that is
to be overlaid and select the data type "AT". The editor creates the overlay, and you can
then choose the data type, struct, or array that you wish to use for the overlay.

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Example
This example shows the input parameters of a standard-access FB. The byte tag B1 is
overlaid with an array of Booleans:

Another example is a DWord tag overlaid with a Struct, which includes a Word, Byte, and
two Booleans:

The Offset column of the block interface shows the location of the overlaid data types
relative to the original tag.
You can address the overlay types directly in the program logic:
LAD

FBD

SCL
IF #OV[1] THEN
...
END_IF;
IF #DW1_Struct.W1 = W#16#000C THEN
...
END_IF;
out1 := #DW1_Struct.B1;

IF #OV[4] AND #DW1_Struct.BO2 THEN
...
END_IF;

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Rules
● Overlaying of tags is only possible in FB and FC blocks with standard (not optimized)
access.
● You can overlay parameters for all block types and all declaration sections.
● You can use an overlaid parameter like any other block parameter.
● You cannot overlay parameters of type VARIANT.
● The size of the overlaying parameter must be less than or equal to the size of the overlaid
parameter.
● You must declare the overlaying variable immediately after the variable that it overlays
and select the keyword "AT" as the initial data type selection.

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5.5

Using a memory card
Note
The CPU supports only the pre-formatted SIMATIC memory cards (Page 1546).
Before you copy any program to the formatted memory card, delete any previously saved
program from the memory card.
Use the memory card either as a transfer card or as a program card. Any program that you
copy to the memory card contains all of the code blocks and data blocks, any technology
objects, and the device configuration. A copied program does not contain force values. The
force values are not part of the program, but are stored in the load memory, whether the
internal load memory of the CPU, or the external load memory (a program card). If you insert
a program card in the CPU, STEP 7 then applies the force values only to the external load
memory on the program card.
● Use a transfer card (Page 142) to copy a program to the internal load memory of the CPU
without using STEP 7. After you insert the transfer card, the CPU first erases the user
program and any force values from the internal load memory, and then copies the
program from the transfer card to the internal load memory. When the transfer process is
complete, you must remove the transfer card.
You can use an empty transfer card to access a password-protected CPU when the
password has been lost or forgotten (Page 151). Inserting the empty transfer card deletes
the password-protected program in the internal load memory of the CPU. You can then
download a new program to the CPU.
● Use a program card (Page 145) as external load memory for the CPU. Inserting a
program card in the CPU erases all of the CPU internal load memory (the user program
and any force values). The CPU then executes the program in external load memory (the
program card). Downloading to a CPU that has a program card updates only the external
load memory (the program card).
Because the internal load memory of the CPU was erased when you inserted the
program card, the program card must remain in the CPU. If you remove the program
card, the CPU goes to STOP mode. (The error LED flashes to indicate that program card
has been removed.)
You also use a memory card when downloading firmware updates (Page 148).

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5.5.1

Inserting a memory card in the CPU
NOTICE
Protect memory card and receptacle from electrostatic discharge
Electrostatic discharge can damage the memory card or the receptacle on the CPU.
Make contact with a grounded conductive pad and/or wear a grounded wrist strap when
you handle the memory card. Store the memory card in a conductive container.

Check that the memory card is not write-protected. Slide the protection
switch away from the "Lock" position.
Note that if you do insert a write-protected memory card into the CPU,
STEP 7 will display a diagnostic message on the next power up alerting you
to that fact. The CPU will power up without failure, but instructions involving
recipes or data logs, for example, will return errors if the card is writeprotected.

WARNING
Verify that the CPU is not running a process before inserting the memory card.
If you insert a memory card (whether configured as a program card, transfer card, or
firmware update card) into a running CPU, the CPU goes immediately to STOP mode,
which might cause process disruption that could result in death or severe personal injury.
Before inserting or removing a memory card, always ensure that the CPU is not actively
controlling a machine or process. Always install an emergency stop circuit for your
application or process.
Note
Do not insert V3.0 program transfer cards into S7-1200 V4.0 CPUs.
Version 3.0 program transfer cards are not compatible with version S7-1200 V4.0 CPUs.
Inserting a memory card that contains a V3.0 program causes a CPU error.
If you do insert an invalid version program transfer card (Page 142), you should remove the
card, and perform a STOP to RUN transition, a memory reset (MRES), or cycle power. After
you recover the CPU from the error condition, you can download a valid V4.0 CPU program.
To transfer a V3.0 program to a V4.0 program, you must use the TIA Portal to Change
Device in the Hardware Configuration.
Note
If you insert a memory card with the CPU in STOP mode, the diagnostic buffer displays a
message that the memory card evaluation has been initiated. The CPU will evaluate the
memory card the next time you either change the CPU to RUN mode, reset the CPU
memory with an MRES, or power-cycle the CPU.

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Table 5- 41

Inserting a memory card

To insert a memory card, open the top CPU
door and insert the memory card in the slot. A
push-push type connector allows for easy
insertion and removal.
The memory card is keyed for proper installation.

CPU behavior when you insert a memory card
When you insert a memory card in the CPU, the CPU peforms the following steps:
1. Transitions to STOP mode (if not already in STOP mode)
2. Prompts for one of the following choices:
– Power cycle
– Transition to RUN mode
– Perform a memory reset
3. Evaluates the card

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How the CPU evaluates the memory card
If you do not configure the CPU to "Disable copy from internal load memory to external load
memory" in the Protection properties of the device configuration (Page 212), the CPU
determines what type of memory card you inserted:
● Empty memory card: A blank memory card does not have a job file (S7_JOB.S7S). If you
insert a blank memory card, the CPU adds a program job file. It then copies internal load
memory to external load memory (the program file on the memory card) and erases
internal load memory.
● Blank program card: A blank program card has a program job file that is empty. In this
case, the CPU copies internal load memory to external load memory (the program file on
the memory card) and erases internal load memory.
If you configured the CPU to "Disable copy from internal load memory to external load
memory" in the Protection properties of the device configuration, the CPU behaves as
follows:
● Empty memory card: A blank memory card does not have a job file (S7_JOB.S7S). If you
insert a blank memory card, the CPU does nothing. It does not create a program job file
and it does not copy internal load memory to external load memory (the program file on
the memory card). It does not erase internal load memory.
● Blank program card: A blank program card has a program job file that is empty. In this
case, the CPU performs no action. It does not copy internal load memory to external load
memory (the program file on the memory card). It does not erase internal load memory.
If you insert a program card (Page 145), transfer card (Page 142), or card that contains a
firmware update (Page 148)into the CPU, the configuration setting for "Disable copy from
internal load memory to external load memory" has no effect on how the CPU evaluates the
memory card.

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5.5.2

Configuring the startup parameter of the CPU before copying the project to the
memory card
When you copy a program to a transfer card or a program card, the program includes the
startup parameter for the CPU. Before copying the program to the memory card, always
ensure that you have configured the operating mode for the CPU following a power-cycle.
Select whether the CPU starts in STOP mode, RUN mode, or in the previous mode (prior to
the power cycle).

5.5.3

Transfer card
NOTICE
Protect memory card and receptacle from electrostatic discharge
Electrostatic discharge can damage the memory card or the receptacle on the CPU.
Make contact with a grounded conductive pad and/or wear a grounded wrist strap
whenever you handle the memory card. Store the memory card in a conductive container.

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Creating a transfer card
Always remember to configure the startup parameter of the CPU (Page 142) before copying
a program to the transfer card. To create a transfer card, follow these steps:
1. Insert a blank SIMATIC memory card that is not write-protected into an SD card
reader/writer attached to your computer. (If the card is write-protected, slide the
protection switch away from the "Lock" position.)
If you are reusing a SIMATIC memory card that contains a user program, data logs,
recipes, or a firmware update, you must delete the files before reusing the card. Use
Windows Explorer to display the contents of the memory card and delete the
"S7_JOB.S7S" file and also delete any existing folders (such as
"SIMATIC.S7S","FWUPDATE.S7S", "DataLogs", and "Recipes").
NOTICE
Do NOT delete the hidden files "__LOG__" and "crdinfo.bin" from the memory card.
The "__LOG__" and "crdinfo.bin" files are required for the memory card. If you delete
these files, you cannot use the memory card with the CPU.
2. In the Project tree (Project view), expand the "SIMATIC Card Reader" folder and select
your card reader.
3. Display the "Memory card" dialog by right-clicking the drive letter corresponding to the
memory card in the card reader and selecting "Properties" from the context menu.
4. In the "Memory card" dialog, select "Transfer" from the "Card type" drop-down menu.
At this point, STEP 7 creates the empty transfer card. If you are creating an empty
transfer card, such as to recover from a lost CPU password (Page 151), remove the
transfer card from the card reader.

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6. In the "Load preview" dialog, click the "Load" button to copy the CPU device to the
memory card.
7. When the dialog displays a message that the CPU device (program) has been loaded
without errors, click the "Finish" button.

Using a transfer card
WARNING
Verify that the CPU is not actively running a process before inserting the memory card.
Inserting a memory card will cause the CPU to go to STOP mode, which could affect the
operation of an online process or machine. Unexpected operation of a process or machine
could result in death or injury to personnel and/or property damage.
Before inserting a transfer card, always ensure that the CPU is in STOP mode and your
process is in a safe state.
Note
Do not insert V3.0 program transfer cards into later model CPUs.
Version 3.0 program transfer cards are not compatible with later model S7-1200 CPUs.
Inserting a memory card that contains a V3.0 program causes a CPU error.
If you do insert an invalid version program transfer card, then remove the card, perform a
STOP to RUN transition, a memory reset (MRES), or cycle power. After you recover the
CPU from the error condition, you can download a valid CPU program
To transfer the program to a CPU, follow these steps:
1. Insert the transfer card into the CPU (Page 139). If the CPU is in RUN, the CPU will go to
STOP mode. The maintenance (MAINT) LED flashes to indicate that the memory card
needs to be evaluated.
2. Power-cycle the CPU to evaluate the memory card. Alternative methods for rebooting the
CPU are to perform either a STOP-to-RUN transition or a memory reset (MRES) from
STEP 7.
3. After the rebooting and evaluating the memory card, the CPU copies the program to the
internal load memory of the CPU.
The RUN/STOP LED alternately flashes green and yellow to indicate that the program is
being copied. When the RUN/STOP LED turns on (solid yellow) and the MAINT LED
flashes, the copy process has finished. You can then remove the memory card.
4. Reboot the CPU (either by restoring power or by the alternative methods for rebooting) to
evaluate the new program that was transferred to internal load memory.
The CPU then goes to the start-up mode (RUN or STOP) that you configured for the project.
Note
You must remove the transfer card before setting the CPU to RUN mode.

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5.5.4

Program card
NOTICE
Electrostatic discharge can damage the memory card or the receptacle on the CPU.
Make contact with a grounded conductive pad and/or wear a grounded wrist strap when
you handle the memory card. Store the memory card in a conductive container.

Check that the memory card is not write-protected. Slide the protection
switch away from the "Lock" position.
Before you copy any program elements to the program card, delete any
previously saved programs from the memory card.

Creating a program card
When used as a program card, the memory card is the external load memory of the CPU. If
you remove the program card, the internal load memory of the CPU is empty.
Note
If you insert a blank memory card into the CPU and perform a memory card evaluation by
either power cycling the CPU, performing a STOP to RUN transition, or performing a
memory reset (MRES), the program and force values in internal load memory of the CPU are
copied to the memory card. (The memory card is now a program card.) After the copy has
been completed, the program in internal load memory of the CPU is then erased. The CPU
then goes to the configured startup mode (RUN or STOP).

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Always remember to configure the startup parameter of the CPU (Page 142) before copying
a project to the program card. To create a program card, follow these steps:
1. Insert a blank SIMATIC memory card that is not write-protected into an SD card
reader/writer attached to your computer. (If the card is write-protected, slide the
protection switch away from the "Lock" position.)
If you are reusing a SIMATIC memory card that contains a user program, data logs,
recipes, or a firmware update, you must delete the files before reusing the card. Use
Windows Explorer to display the contents of the memory card and delete the
"S7_JOB.S7S" file and also delete any existing folders (such as
"SIMATIC.S7S","FWUPDATE.S7S", "DataLogs", and "Recipes").
NOTICE
Do NOT delete the hidden files "__LOG__" and "crdinfo.bin" from the memory card.
The "__LOG__" and "crdinfo.bin" files are required for the memory card. If you delete
these files, you cannot use the memory card with the CPU.
2. In the Project tree (Project view), expand the "SIMATIC Card Reader" folder and select
your card reader.
3. Display the "Memory card" dialog by right-clicking the drive letter corresponding to the
memory card in the card reader and selecting "Properties" from the context menu.
4. In the "Memory card" dialog, select "Program" from the drop-down menu.

5. Add the program by selecting the CPU device (such as PLC_1 [CPU 1214C DC/DC/DC])
in the Project tree and dragging the CPU device to the memory card. (Another method is
to copy the CPU device and paste it to the memory card.) Copying the CPU device to the
memory card opens the "Load preview" dialog.
6. In the "Load preview" dialog, click the "Load" button to copy the CPU device to the
memory card.
7. When the dialog displays a message that the CPU device (program) has been loaded
without errors, click the "Finish" button.

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Using a program card as the load memory for your CPU
WARNING
Risks associated with inserting a program card
Verify that the CPU is not actively running a process before inserting the memory card.
Inserting a memory card will cause the CPU to go to STOP mode, which could affect the
operation of an online process or machine. Unexpected operation of a process or machine
could result in death or injury to personnel and/or property damage.
Before inserting a memory card, always ensure that the CPU is offline and in a safe state.
To use a program card with your CPU, follow these steps:
1. Insert the program card into the CPU. If the CPU is in RUN mode, the CPU goes to STOP
mode. The maintenance (MAINT) LED flashes to indicate that the memory card needs to
be evaluated.
2. Power-cycle the CPU to evaluate the memory card. Alternative methods for rebooting the
CPU are to perform either a STOP-to-RUN transition or a memory reset (MRES) from
STEP 7.
3. After the CPU reboots and evaluates the program card, the CPU erases the internal load
memory of the CPU.
The CPU then goes to the start-up mode (RUN or STOP) that you configured for the CPU.
The program card must remain in the CPU. Removing the program card leaves the CPU with
no program in internal load memory.
WARNING
Risks associated with removing a program card
If you remove the program card, the CPU loses its external load memory and generates an
error. The CPU goes to STOP mode and flashes the error LED.
Control devices can fail in an unsafe condition, resulting in unexpected operation of
controlled equipment. Such unexpected operations could result in death or serious injury to
personnel, and/or damage to equipment.
Do not remove the program card without understanding that you are removing the program
from CPU.

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5.5.5

Firmware update
You can use a SIMATIC memory card for performing a firmware update.
NOTICE
Protect memory card and receptacle from electrostatic discharge
Electrostatic discharge can damage the memory card or the receptacle on the CPU.
Make contact with a grounded conductive pad and/or wear a grounded wrist strap
whenever you handle the memory card. Store the memory card in a conductive container.
You use a SIMATIC memory card when downloading firmware updates from Siemens
Industry Online Support (http://support.industry.siemens.com). From this Web site, navigate
to "Downloads". From there search for the specific type of module that you need to update.
Alternatively, you can access the S7-1200 downloads Web page
(https://support.industry.siemens.com/cs/ww/en/ps/13683/dl) directly.
Note
You cannot update an S7-1200 CPU V3.0 or earlier to S7-1200 V4.0 or V4.1 by firmware
update.
You can also perform a firmware update by one of these methods:
● Using the online and diagnostic tools of STEP 7 (Page 1318)
● Using the Web server "Module Information" standard Web page (Page 1023)
● Using the SIMATIC Automation Tool
(https://support.industry.siemens.com/cs/ww/en/view/98161300)
NOTICE
Do not use the Windows formatter utility or any other formatting utility to reformat the
memory card.
If a Siemens memory card is reformatted using the Microsoft Windows formatter utility, then
the memory card will no longer be usable by a S7-1200 CPU.

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To download the firmware update to your memory card, follow these steps:
1. Insert a blank SIMATIC memory card that is not write-protected into an SD card
reader/writer attached to your computer. (If the card is write-protected, slide the
protection switch away from the "Lock" position.)
You can reuse a SIMATIC memory card that contains a user program or another firmware
update, but you must delete some of the files on the memory card.
To reuse a memory card, you must delete the "S7_JOB.S7S" file and any existing "Data
Logs" folders or any folder (such as "SIMATIC.S7S" or "FWUPDATE.S7S") before
downloading the firmware update. Use Windows Explorer to display the contents of the
memory card and to delete the file and folders.
NOTICE
Do NOT delete the hidden files "__LOG__" and "crdinfo.bin" from the memory card.
The "__LOG__" and "crdinfo.bin" files are required for the memory card. If you delete
these files, you cannot use the memory card with the CPU.
2. Select the zip file for the firmware update that corresponds to your module, and download
it to your computer. Double-click the file, set the file destination path to be the root
directory of the SIMATIC memory card, and start the extraction process. After the
extraction is complete, the root directory (folder) of the memory card will contain a
"FWUPDATE.S7S" directory and the "S7_JOB.S7S" file.
3. Safely eject the card from the card reader/writer.
To install the firmware update, follow these steps:
WARNING
Verify that the CPU is not actively running a process before installing the firmware update.
Installing the firmware update will cause the CPU to go to STOP mode, which could affect
the operation of an online process or machine. Unexpected operation of a process or
machine could result in death or injury to personnel and/or property damage.
Before inserting the memory card, always ensure that the CPU is offline and in a safe state.
1. Insert the memory card into the CPU. If the CPU is in RUN mode, the CPU then goes to
STOP mode. The maintenance (MAINT) LED flashes to indicate that the memory card
needs to be evaluated.
2. Power-cycle the CPU to start the firmware update. Alternative methods for rebooting the
CPU are to perform either a STOP-to-RUN transition or a memory reset (MRES) from
STEP 7.
Note
To complete the firmware upgrade for the module, you must ensure that the external 24 V
DC power to the module remains on.

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After the CPU reboots, the firmware update starts. The RUN/STOP LED alternately
flashes green and yellow to indicate that the update is being copied. When the
RUN/STOP LED turns on (solid yellow) and the MAINT LED flashes, the copy process
has finished. You must then remove the memory card.
3. After removing the memory card, reboot the CPU again (either by restoring power or by
the alternative methods for rebooting) to load the new firmware.
The user program and hardware configuration are not affected by the firmware update.
When the CPU is powered up, the CPU enters the configured start-up state. (If the startup
mode for your CPU was configured to "Warm restart - mode before POWER OFF", the CPU
will be in STOP mode because the last state of the CPU was STOP.)
Note
Updating multiple modules connected to CPU
If your hardware configuration contains multiple modules that correspond to a single
firmware update file on the memory card, the CPU applies the updates to all applicable
modules (CM, SM, and SB) in configuration order, that is, by increasing order of the module
position in Device Configuration in STEP 7.
If you have downloaded multiple firmware updates to the memory card for multiple modules,
the CPU applies the updates in the order in which you downloaded them to the memory
card.

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5.6

Recovery from a lost password
If you have lost the password for a password-protected CPU, use an empty transfer card to
delete the password-protected program. The empty transfer card erases the internal load
memory of the CPU. You can then download a new user program from STEP 7 to the CPU.
For information about the creation and use of an empty transfer card, see the section of
transfer cards (Page 142).
WARNING
Verify that the CPU is not actively running a process before inserting the memory card
If you insert a transfer card in a running CPU, the CPU goes to STOP. Control devices can
fail in an unsafe condition, resulting in unexpected operation of controlled equipment. Such
unexpected operations could result in death or serious injury to personnel, and/or damage
to equipment.
Before inserting a transfer card, always ensure that the CPU is in STOP mode and your
process is in a safe state.
You must remove the transfer card before setting the CPU to RUN mode.

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Device configuration

You create the device configuration for your PLC by adding a CPU and additional modules to
your project.

①
②
③
④
⑤

Communication module (CM) or communication processor (CP): Up to 3, inserted in slots 101,
102, and 103
CPU: Slot 1
PROFINET port of CPU
Signal board (SB), communication board (CB) or battery board (BB): up to 1, inserted in the
CPU
Signal module (SM) for digital or analog I/O: up to 8, inserted in slots 2 through 9
(CPU 1214C, CPU 1215C and CPU 1217C allow 8, CPU 1212C allows 2, CPU 1211C does not
allow any)

Configuration control
Device configuration for the S7-1200 also supports "configuration control (Page 159)" where
you can configure a maximum configuration for a project including modules that you might
not actually use. This feature, sometimes also called "option handling", allows you to
configure a maximum configuration that you might use with variations in the installed
modules in multiple applications.

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6.1 Inserting a CPU

6.1

Inserting a CPU
You can insert a CPU into your project from either the Portal view or the
Project view of STEP 7:
• In the Portal view, select "Devices
& Networks" and click "Add new
device".
• In the Project view, under the
project name, double-click "Add
new device".

Be sure you insert the correct model and firmware version from the list. Selecting the CPU
from the "Add new device" dialog creates the rack and CPU.
Note
With STEP 7 V14, you cannot add a V1.0 S7-1200 CPU to your project.

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"Add new device" dialog

Device view of the hardware
configuration

Selecting the CPU in the Device
view displays the CPU properties in the inspector window.
The CPU does not have a preconfigured IP address. You must
manually assign an IP address
for the CPU during the device
configuration. If your CPU is
connected to a router on the
network, you also enter the IP
address for a router.

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6.2 Uploading the configuration of a connected CPU

6.2

Uploading the configuration of a connected CPU
STEP 7 provides two methods for uploading the hardware configuration of a connected
CPU:
● Uploading the connected device as a new station
● Configuring an unspecified CPU and detecting the hardware configuration of the
connected CPU
Note, however, that the first method uploads both the hardware configuration and the
software of the connected CPU.

Uploading a device as a new station
To upload a connected device as a new station, follow these steps:
1. Expand your communications interface from the "Online access" node of the project tree.
2. Double-click "Update accessible devices".
3. Select the PLC from the detected devices.

4. From the Online menu of STEP 7, select the "Upload device as new station (hardware
and software)" menu command.
STEP 7 uploads both the hardware configuration and the program blocks.

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6.2 Uploading the configuration of a connected CPU

Detecting the hardware configuration of an unspecified CPU
If you are connected to a CPU, you can upload the
configuration of that CPU, including any modules, to
your project. Simply create a new project and select
the "unspecified CPU" instead of selecting a specific
CPU. (You can also skip the device configuration entirely by selecting the "Create a PLC program" from the
"First steps". STEP 7 then automatically creates an
unspecified CPU.)
From the program editor, you select the "Hardware
detection" command from the "Online" menu.

From the device configuration editor, you select the option for detecting the configuration of
the connected device.

After you select the CPU from the online dialog and click the Load button, STEP 7 uploads
the hardware configuration from the CPU, including any modules (SM, SB, or CM). You can
then configure the parameters for the CPU and the modules (Page 170).

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6.3 Adding modules to the configuration

6.3

Adding modules to the configuration
Use the hardware catalog to add modules to the CPU:
● Signal module (SM) provides additional digital or analog I/O points. These modules are
connected to the right side of the CPU.
● Signal board (SB) provides just a few additional I/O points for the CPU. The SB is
installed on the front of the CPU.
● Battery Board 1297 (BB) provides long-term backup of the realtime clock. The BB is
installed on the front of the CPU.
● Communication board (CB) provides an additional communication port (such as RS485).
The CB is installed on the front of the CPU.
● Communication module (CM) and communication processor (CP) provide an additional
communication port, such as for PROFIBUS or GPRS. These modules are connected to
the left side of the CPU.
To insert a module into the device configuration, select the module in the hardware catalog
and either double-click or drag the module to the highlighted slot. You must add the modules
to the device configuration and download the hardware configuration to the CPU for the
modules to be functional.
Table 6- 1
Module

Adding a module to the device configuration
Select the module

Insert the module

Result

SB, BB
or CB

CM or
CP

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6.4 Configuration control
With the "configuration control" feature (Page 159), you can add signal modules and signal
boards to your device configuration that might not correspond to the actual hardware for a
specific application, but that will be used in related applications that share a common user
program, CPU model, and perhaps some of the configured modules.

6.4

Configuration control

6.4.1

Advantages and applications of configuration control
Configuration control can be a useful solution when you create an automation solution
(machine) that you intend to use with variations in multiple installations.
You can load a STEP 7 device configuration and user program to different installed PLC
configurations. You only need to make a few easy adaptations to make the STEP 7 project
correspond to the actual installation.

6.4.2

Configuring the central installation and optional modules
Configuration control with STEP 7 and the S7-1200 enables you to configure a maximum
configuration for a standard machine and to operate versions (options) that use a subset of
this configuration. The PROFINET with STEP 7 manual
(http://support.automation.siemens.com/WW/view/en/49948856) refers to these types of
projects as "standard machine projects".
A control data record that you program in the startup program block notifies the CPU as to
which modules are missing in the real installation as compared to the configuration or which
modules are located in different slots as compared to the configuration. Configuration control
does not have an impact on the parameter assignment of the modules.
Configuration control gives you the flexibility to vary the installation as long as you can derive
the real configuration from the maximum device configuration in STEP 7.
To activate configuration control and structure the required control data record, follow these
steps:
1. Optionally, reset the CPU to factory settings to ensure that an incompatible control data
record is not present in the CPU.
2. Select the CPU in device configuration in STEP 7.
3. From the Configuration control node in the CPU properties, select the "Enable
reconfiguration of device with user program" check box.

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4. Create a PLC data type to contain the control data record. Configure it as a struct that
includes four USints for configuration control information and additional USints to
correspond to the slots of a maximum S7-1200 device configuration, as follows:

5. Create a data block of the PLC data type that you created.

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6. In this data block, configure the Block_length, Block_ID, Version, and Subversion as
shown below. Configure the values for the slots based on their presence or absence and
position in your actual installation:
– 0: Configured module is not present in the actual configuration. (The slot is empty.)
– 1 to 9, 101 to 103: The actual slot position for the configured slot
– 255: The STEP 7 device configuration does not include a module in this slot.
Note
Configuration control not available for HSCs and PTOs on the signal board
If you have a signal board in the CPU that you configure for HSCs or PTOs, you must not
disable it with a "0" in Slot_1 of the configuration control data record. Configured HSC and
PTO devices of the CPU are mandatory regarding configuration control.

See Example of configuration control (Page 166) for an explanation of how to assign the
slot values.

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7. In the startup OB, call the extended WRREC (Write data record) instruction to transfer the
control data record that you created to index 196 of hardware ID 33. Use a label and JMP
(jump) instruction to wait for the WRREC instruction to complete.
Network 1:

Network 2:

Note
Configuration control is not in effect until the WRREC instruction transfers the control data
record in the startup OB. If you have enabled configuration control and the CPU does not
have the control data record, it will go to STOP mode when it exits STARTUP mode. Be sure
that you program the startup OB to transfer the control data record.

Module arrangement
The following table shows the slot number assignment:
Slot

Modules

Signal board or communication board (CPU annex card)

2 to 9

Signal modules

101 to 103

Communication modules

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Control data record
A control data record 196 contains the slot assignment and represents the actual
configuration, as shown below:
Byte

Element

Value

Explanation

Block length

Header

Block ID

196

Version

Subversion

Assignment of CPU annex card

Actual annex card, 0, or 255*

Control element

Assignment of configured slot 2

Actual slot, 0, or 255*

...

Assignment of configured slot 9

Actual slot, 0, or 255*

Describes in each element which
real slot in the device is assigned to
the configured slot.

Assignment of configured slot 101

Actual slot or 255*

Assignment of configured slot 102

Actual slot or 255*

Assignment of configured slot 103

Actual slot or 255*

Unlike signal modules, the actual
slot for physically-present communication modules must be the same
as the configured slot.

*Slot values:
0: Configured module is not present in the actual configuration. (The slot is empty.)
1 to 9, 101 to 103: The actual slot position for the configured slot
255: The STEP 7 device configuration does not include a module in this slot.

Note
Alternative to creating a PLC tag type
As an alternative to creating a custom PLC tag type, you can create a data block directly with
all of the structure elements of a control data record. You could even configure multiple
structs in this data block to serve as multiple control data record configurations. Either
implementation is an effective way to transfer the control data record during startup.

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Rules
Observe the following rules:
● Configuration control does not support position changes for communication modules. The
control data record slot positions for slots 101 to 103 must correspond to the actual
installation. If you have not configured a module for the slot in your device configuration,
enter 255 for that slot position in the control data record. If you have configured a module
for the slot, enter the configured slot as the actual slot for that slot position.
● F-I/O modules do not support configuration control. The control data record slot positions
for an F-I/O module must equal the configured slot position for the F-I/O module. If you
attempt to move or delete a configured F-I/O module using the control data record, then
all actually-installed F-I/O modules will raise a "parameter assignment" error and disallow
exchange.
● You cannot have embedded empty (unused) slots between filled (used) slots. For
example, if the actual configuration has a module in slot 4, then the actual configuration
must also have modules in slots 2 and 3. Correspondingly, if the actual configuration has
a communication module in slot 102, then the actual configuration must also have a
module in slot 101.
● If you have enabled configuration control, the CPU is not ready for operation without a
control data record. The CPU returns from startup to STOP if a startup OB does not
transfer a valid control data record. The CPU does not initialize the central I/O in this case
and enters the cause for the STOP mode in the diagnostics buffer.
● The CPU saves a successfully-transferred control data record in retentive memory, which
means that it is not necessary to write the control data record 196 again at a restart if you
have not changed the configuration.
● Each real slot must be present only once in the control data record.
● You can only assign a real slot to one configured slot.
Note
Modifying a configuration
The writing of a control data record with a modified configuration triggers the following
automatic reaction by the CPU: Memory reset with subsequent startup with this modified
configuration.
As a result of this reaction, the CPU deletes the original control data record and saves the
new control data record retentively.

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Behavior during operation
For the online display and for the display in the diagnostics buffer (module OK or module
faulty), STEP 7 uses the device configuration and not the differing real configuration.
Example: A module outputs diagnostics data. This module is configured in slot 4, but is
actually inserted in slot 3. The online view indicates that configured slot 4 is faulty. In the real
configuration, the module at slot 3 indicates an error by its LED display.
If you have configured modules as missing in the control data record (0 entry), the
automation system behaves as follows:
● Modules designated as not present in the control data record do not supply diagnostics
and their status is always OK. The value status is OK.
● Direct writing access to the outputs or writing access to the process image of outputs that
are not present proceeds with no effect; the CPU reports no access error.
● Direct read access to the inputs or read access to the process image of inputs that are
not present results in a value "0" for each input; the CPU reports no access error.
● Writing a data record to a module that is not present proceeds with no effect; the CPU
reports no error.
● Attempting to read a data record from module that is not present resuls in an error
because the CPU cannot return a valid data record.

Error messages
The CPU returns the following error messages if an error occurs during writing of the control
data record:
Error code

Meaning

16#80B1

Invalid length; the length information in the control data record is not correct.

16#80B5

Configuration control parameters not assigned

16#80E2

Data record was transferred in the wrong OB context. The data record must be transferred in the
startup OB.

16#80B0

Block type (byte 2) of control data record is not equal to 196.

16#80B8

Parameter error; module signals invalid parameters, for example:
•

The control data record attempts to modify the configuration of a communication module or a
communication annex card. The real configuration for communication modules and a communication annex card must equal the STEP 7 configuration.

•

The assigned value for an unconfigured slot in the STEP 7 project is not equal to 255.

•

The assigned value for a configured slot is out of range.

•

The assigned configuration has an "internal" empty slot, for example, slot n is assigned and slot
n-1 is not assigned.

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6.4.3

Example of configuration control
This example describes a configuration consisting of a CPU and three I/O modules.The
module at slot 3 is not present in the first actual installation, so you use configuration control
to "hide" it.
In the second installation, the application includes the module that was initially hidden but
now includes it in the last slot. A modified control data record provides the information about
the slot assignments of the modules.

Example: Actual installation with configured but unused module
The device configuration contains all modules that can be present in an actual installation
(maximum configuration). In this case, the module that is in slot 3 in the device configuration
is not present in the real installation.

Figure 6-1

Device configuration of maximum installation with three signal modules

Figure 6-2

Actual installation with module configured in slot 3 absent, and module configured for slot
4 in actual slot 3

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To indicate the absence of the missing module, you must configure slot 3 in the control data
record with 0.

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Example: Actual installation with module subsequently added to a different slot
In the second example, the module in slot 3 of the device configuration is present in the
actual installation but is in slot 4.

Figure 6-3

Device configuration compared to actual installation with modules in slots 3 and 4
swapped

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To correlate the device configuration to the actual installation, edit the control data record to
assign the modules to the correct slot positions.

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6.5 Changing a device

6.5

Changing a device
You can change the device type of a configured CPU or module. From Device configuration,
right-click the device and select "Change device" from the context menu. From the dialog,
navigate to and select the CPU or module that you want to replace. The Change device
dialog shows you compatibility information between the two devices.
For considerations on changing devices between different CPU versions, refer to
Exchanging a V3.0 CPU for a V4.2 CPU (Page 1571).

6.6

Configuring the operation of the CPU

6.6.1

Overview
To configure the operational parameters for the CPU, select the CPU in the Device view
(blue outline around whole CPU), and use the "Properties" tab of the inspector window.

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6.6 Configuring the operation of the CPU
Table 6- 2

CPU properties

Property

Description

PROFINET interface

Sets the IP address for the CPU and time synchronization

DI, DO, and AI

Configures the behavior of the local (on-board) digital and analog I/O (for example, digital
input filter times and digital output reaction to a CPU stop).

High-speed counters
(Page 555) and pulse generators (Page 492)

Enables and configures the high-speed counters (HSC) and the pulse generators used for
pulse-train operations (PTO) and pulse-width modulation (PWM)

Startup (Page 87)

When you configure the outputs of the CPU or signal board as pulse generators (for use with
the PWM or motion control instructions), the corresponding output addresses are removed
from the Q memory and cannot be used for other purposes in your user program. If your
user program writes a value to an output used as a pulse generator, the CPU does not write
that value to the physical output.
Startup after POWER ON: Selects the behavior of the CPU following an off-to-on transition,
such as to start in STOP mode or to go to RUN mode after a warm restart
Supported hardware compatibility: Configures the substitution strategy for all system components (SM, SB, CM, CP and CPU):
•

Allow acceptable substitute

• Allow any substitute (default)
Each module internally contains substitution compatibility requirements based on the number of I/O, electrical compatibility, and other corresponding points of comparison. For example, a 16-channel SM could be an acceptable substitute for an 8-channel SM, but an 8channel SM could not be an acceptable substitute for a 16-channel SM. If you select "Allow
acceptable substitute", STEP 7 enforces the substitution rules; otherwise, STEP 7 allows
any substitution.
Parameter assignment time for distributed I/O: Configures a maximum amount of time (default: 60000 ms) for the distributed I/O to be brought online. (The CMs and CPs receive
power and communication parameters from the CPU during startup. This assignment time
allows time for the I/O connected to the CM or CP to be brought online.)
The CPU goes to RUN as soon as the distributed I/O is online, regardless of the assignment
time. If the distributed I/O has not been brought online within this time, the CPU still goes to
RUN--without the distributed I/O.
Note: If your configuration uses a CM 1243-5 (PROFIBUS master), do not set this parameter
below 15 seconds (15000 ms) to ensure that the module can be brought online.
OBs should be interruptible: Configures whether OB execution (for all OBs) in the CPU is
interruptible or non-interruptible (Page 105)
Cycle (Page 109)

Defines a maximum cycle time or a fixed minimum cycle time

Communication load

Allocates a percentage of the CPU time to be dedicated to communication tasks

System and clock memory
(Page 112)

Enables a byte for "system memory" functions and enables a byte for "clock memory" functions (where each bit toggles on and off at a predefined frequency)

Web server (Page 1001)

Enables and configures the Web server feature

Time of day

Selects the time zone and configures daylight saving time

Multilingual support
(Page 175)

Assigns a project language for the Web server to use for displaying diagnostic buffer entry
texts for each of the possible Web server user interface display languages.

Protection (Page 210)

Sets the read/write protection and passwords for accessing the CPU

Configuration control
(Page 159)

Enables configuring a master device configuration that you can control for different actual
device configurations

Connection resources
(Page 801)

Provides a summary of the communication connection resources that are available for the
CPU and the number of connection resources that have been configured

Overview of addresses

Provides a summary of the I/O addresses that have been configured for the CPU

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6.6.2

Configuring digital input filter times
The digital input filters protect your program from responding to unwanted fast changes in
the input signals, as may result from switch contact bounce or electrical noise. The default
filter time of 6.4 ms blocks unwanted transitions from typical mechanical contacts. Different
points in your application can require shorter filter times to detect and respond to inputs from
fast sensors, or longer filter times to block slow contact bounce or longer impulse noise.
An input filter time of 6.4 ms means that a single signal change, from ‘0’ to ‘1’ or from ‘1’ to
‘0’, must continue for approximately 6.4 ms to be detected, and a single high or low pulse
shorter than approximately 6.4 ms is not detected. If an input signal switches between ‘0’
and ‘1’ more rapidly than the filter time, the input point value can change in the user program
when the accumulated duration of new value pulses over old value pulses exceeds the filter
time.
The digital input filter works this way:
● When a "1" is input, it counts up, stopping at the filter time. The image register point
changes from "0" to "1" when the count reaches the filter time.
● When a "0" is input, it counts down, stopping at "0". The image register point changes
from "1" to "0" when the count reaches "0".
● If the input is changing back and forth, the counter will count up some and count down
some. The image register will change when the net accumulation of counts reaches
either the filter time or "0".
● A rapidly-changing signal with more "0’s" than "1’s" will eventually go to "0", and if there
are more "1’s" than "0’s", the image register will eventually change to "1".

Each input point has a single filter configuration that applies to all uses: process inputs,
interrupts, pulse catch, and HSC inputs. To configure input filter times, select "Digital Inputs".

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The default filter time for the digital inputs is 6.4 ms. You can select a filter time from the
Input filters drop-down list. Valid filter times range from 0.1 us to 20.0 ms.
WARNING
Risks with changes to filter time for digital input channel
If you change the filter time for a digital input channel from a previous setting, a new "0"
level input value may need to stay at "0" for up to 20.0 ms before the filter becomes fully
responsive to new inputs. During this time, short "0" pulse events of duration less than 20.0
ms may not be detected or counted.
This changing of filter times can result in unexpected machine or process operation, which
may cause death or serious injury to personnel, and/or damage to equipment.
To ensure that a new filter time goes immediately into effect, a power cycle of the CPU
must be applied.

Configuring filter times for digital inputs used as HSCs
For inputs that you use as high-speed counters (HSCs), change the input filter time to an
appropriate value to avoid missing counts.
Siemens recommends the following settings:
Type of HSC

Recommended input filter time

1 MHz

0.1 microseconds

100 kHz

0.8 microseconds

30 kHz

3.2 microseconds

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6.6.3

Pulse catch
The S7-1200 CPU provides a pulse catch feature for digital input points. The pulse catch
feature allows you to capture high-going pulses or low-going pulses that are of such a short
duration that they would not always be seen when the CPU reads the digital inputs at the
beginning of the scan cycle.
When pulse catch is enabled for an input, a change in state of the input is latched and held
until the next input cycle update. This ensures that a pulse which lasts for a short period of
time will be caught and held until the CPU reads the inputs.
The figure below shows the basic operation of the S7-1200 CPU with and without pulse
catch enabled:

Because the pulse catch function operates on the input after it passes through the input filter,
you must adjust the input filter time so that the pulse is not removed by the filter. The figure
below shows a block diagram of the digital input circuit:

The figure below shows the response of an enabled pulse catch function to various input
conditions. If you have more than one pulse in a given scan, only the first pulse is read. If
you have multiple pulses in a given scan, you should use the rising/falling edge interrupt
events:

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6.7 Configuring multilingual support

6.7

Configuring multilingual support
The Multilingual support settings allow you to assign one of two project languages for each
user interface language for the S7-1200 Web server (Page 1001). You can also configure no
project language for a user interface language.

What is a project language?
The project language is the language that the TIA Portal uses to display user-defined project
texts as network comments and block comments.
You select project languages in the TIA Portal from the Tools > Project languages menu
command for the selected project in the project tree.
You can then configure user texts such as network comments and block comments in each
project language from the Tools > Project texts menu command. Then when you change the
TIA Portal user interface language, the network comments, block comments, and other
multilingual project texts display in the corresponding project language. You set the TIA
Portal user interface language from the Options > Settings project language menu
command.
Project languages and project texts are also configurable from the Languages & resources
node of the project tree.
The Web server can use one or two of the STEP 7 project languages for the display of
diagnostic buffer messages.

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6.8 Configuring the parameters of the modules

Project language correspondence to user interface language in the Web server
The Web server supports the same user interface languages as the TIA Portal; however, it
only supports up to two project languages. You can configure the Web server to use one of
two project languages for diagnostic buffer text entries depending on the user interface
language of the Web server. You configure these settings in the "Multilingual support"
properties in the device configuration of the CPU. (Network comments and block comments
and other multilingual texts are not visible from the Web server.)

In the Multilingual support properties, the user interface languages on the right are not
editable. They are the pre-defined languages that are available for both the TIA Portal and
for the Web server user interfaces. The "Assign project language" setting is configurable and
can be one of two of your configured project languages, or it can be "None". Because the
S7-1200 CPU only supports two project languages, you cannot configure the project
language to be the same as the user interface language for all of the supported user
interface languages.
In the configuration below, the Web server displays diagnostic buffer entries (Page 1022) in
German when the Web server user interface is German, displays no texts for diagnostic
buffer events when the Web server user interface is Spanish, and displays diagnostic buffer
entries in English for all other languages.

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6.8 Configuring the parameters of the modules

6.8

Configuring the parameters of the modules
To configure the operational parameters for the modules, select the module in the Device
view and use the "Properties" tab of the inspector window to configure the parameters for the
module.

Configuring a signal module (SM) or a signal board (SB)
The device configuration for signal modules and signal boards provides the means to
configure the following:
● Digital I/O: You can configure inputs for rising-edge detection or falling-edge detection
(associating each with an event and hardware interrupt) or for "pulse catch" (to stay on
after a momentary pulse) through the next update of the input process image. Outputs
can use a freeze or substitute value.
● Analog I/O: For individual inputs, configure parameters, such as measurement type
(voltage or current), range and smoothing, and to enable underflow or overflow
diagnostics. Analog outputs provide parameters such as output type (voltage or current)
and for diagnostics, such as short circuit (for voltage outputs) or upper/lower limit
diagnostics. You do not configure ranges of analog inputs and outputs in engineering
units on the Properties dialog. You must handle this in your program logic as described in
the topic "Processing of analog values (Page 123)".
● I/O addresses: You configure the start address for the set of inputs and outputs of the
module. You can also assign the inputs and outputs to a process image partition (PIP0,
PIP1, PIP2, PIP3, PIP4) or to automatically update, or to use no process image partition.
See "Execution of the user program" (Page 83) for an explanation of the process image
and process image partitions.

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Configuring a communication interface (CM, CP or CB)
Depending on the type of communication interface, you configure the parameters for the
network.

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6.9 Configuring the CPU for communication

6.9

Configuring the CPU for communication
The S7-1200 is designed to solve your communications and networking needs by supporting
not only the simplest of networks but also supporting more complex networks. The S7-1200
also provides tools that allow you to communicate with other devices, such as printers and
weigh scales which use their own communications protocols.
Use the "Network view" of Device configuration to
create the network connections between the devices in your project. After creating the network
connection, use the "Properties" tab of the inspector window to configure the parameters of the
network.
Refer to "Creating a network connection"
(Page 806) for further information.

In the Properties window, select the "Ethernet
addresses" configuration entry. STEP 7 displays
the Ethernet address configuration dialog, which
associates the software project with the IP address of the CPU that will receive that project.
Note: The S7-1200 CPU does not have a preconfigured IP address. You must manually assign
an IP address for the CPU.
Refer to "Assigning Internet Protocol (IP) addresses" (Page 810) for further information.

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6.10 Time synchronization
For the TCP, ISO-on-TCP, and UDP Ethernet
protocols, use the "Properties" of the instruction
(TSEND_C, TRCV_C, or TCON) to configure the
"Local/Partner" connections.
The figure shows the "Connection properties" of
the "Configuration tab" for an ISO-on-TCP connection.
Refer to "Configuring the Local/Partner connection
path" (Page 807) for further information.

After completing the configuration, download the
project to the CPU. All IP addresses are configured when you download the project.
Refer to "Testing the PROFINET network"
(Page 819) for further information.

Note
To make a connection to your CPU, your network interface card (NIC) and the CPU must be
on the same class of network and on the same subnet. You can either set up your network
interface card to match the default IP address of the CPU, or you can change the IP address
of the CPU to match the network class and subnet of your network interface card.
Refer to "Assigning Internet Protocol (IP) addresses" (Page 810) for information about how
to accomplish this.

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6.10 Time synchronization

6.10

Time synchronization
The objective of time synchronization of the time-of-day clocks is to have one master clock to
which all other local clocks are synchronized. Not only are the clocks synchronized initially,
but they are re-synchronized periodically to avoid the effects of drift over time.
In the case of the S7-1200 and its local base components, only the CPU and some of the CP
modules have time-of-day clocks that may need to be synchronized. In general, the CPU’s
time-of-day clock can be synchronized to an external master clock. The external master
clock might supply the time of day using an NTP server or through a CP in the local rack of
the S7-1200 that is connected to a SCADA system which includes a master clock.
Refer to S7-1200 CPs (https://support.industry.siemens.com/cs/us/en/ps) at Siemens
Industry Online Support, Product Support for further information on all S7-1200 CPs that
support the Time sychronization function.

Setting the time-of-day clock
There are three ways to set the time-of-day clock in the S7-1200 CPU:
● Using the NTP server (Page 822)
● Using the Engineering System (ES)
● From the user program
● Using an HMI panel
You configure time synchronization of the CP modules to the CPU’s clock by selecting the
"CPU synchronizes the modules of the device." check box as shown in the following figure:

By default, neither time synchronization using the NTP server nor time synchronization of the
CP clocks to the CPU’s clock is enabled.
You configure time synchronization of the CPU’s clock and time synchronization of the CP
clocks independently. Consequently, you can enable time synchronization of the CP clocks
by the CPU when the CPU’s clock is set by any internal or external method.
You can select the update interval using the NTP server. The update interval of the NTP
server is set to 10 seconds by default.

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6.10 Time synchronization
When you activate time synchronization in a module, the Engineering Station (ES) prompts
you to select the "CPU synchronizes the modules of the device." if you have not already
selected the check box in the CPU’s "Time synchronization" dialog. The ES also warns you if
you configured more than one master clock source for time synchronization (for example,
you activated time synchronization on more than one CP or on both the CPU and a module).
Note
Activating time synchronization on a CP causes the CP to set the CPU’s clock. Selecting the
"CPU synchronizes the modules of the device" check box in the CPU’s "Time
synchronization" dialog causes the CP modules to automatically synchronize to the CPU’s
clock.
Note
You should assign only one time source for the control system.

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Programming concepts
7.1

Guidelines for designing a PLC system
When designing a PLC system, you can choose from a variety of methods and criteria. The
following general guidelines can apply to many design projects. Of course, you must follow
the directives of your own company's procedures and the accepted practices of your own
training and location.

Table 7- 1

Guidelines for designing a PLC system

Recommended steps

Tasks

Partition your process
or machine

Divide your process or machine into sections that have a level of independence from each other.
These partitions determine the boundaries between controllers and influence the functional description specifications and the assignment of resources.

Create the functional
specifications

Write the descriptions of operation for each section of the process or machine, such as the I/O
points, the functional description of the operation, the states that must be achieved before allowing action for each actuator (such as a solenoid, a motor, or a drive), a description of the operator
interface, and any interfaces with other sections of the process or machine.

Design the safety circuits

Identify any equipment that might require hard-wired logic for safety. Remember that control
devices can fail in an unsafe manner, which can produce unexpected startup or change in the
operation of machinery. Where unexpected or incorrect operation of the machinery could result in
physical injury to people or significant property damage, consider the implementation of electromechanical overrides (which operate independently of the PLC) to prevent unsafe operations.
The following tasks should be included in the design of safety circuits:

Plan system security

•

Identify any improper or unexpected operation of actuators that could be hazardous.

•

Identify the conditions that would assure the operation is not hazardous, and determine how
to detect these conditions independently of the PLC.

•

Identify how the PLC affects the process when power is applied and removed, and also identify how and when errors are detected. Use this information only for designing the normal and
expected abnormal operation. You should not rely on this "best case" scenario for safety purposes.

•

Design the manual or electromechanical safety overrides that block the hazardous operation
independent of the PLC.

•

Provide the appropriate status information from the independent circuits to the PLC so that
the program and any operator interfaces have necessary information.

•

Identify any other safety-related requirements for safe operation of the process.

Determine what level of protection (Page 210) you require for access to your process. You can
password-protect CPUs and program blocks from unauthorized access.

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7.1 Guidelines for designing a PLC system

Recommended steps

Tasks

Specify the operator
stations

Based on the requirements of the functional specifications, create the following drawings of the
operator stations:

Create the configuration drawings

Create a list of symbolic names

•

Overview drawing that shows the location of each operator station in relation to the process
or machine.

•

Mechanical layout drawing of the devices for the operator station, such as display, switches,
and lights.

•

Electrical drawings with the associated I/O of the PLC and signal modules.

Based on the requirements of the functional specification, create configuration drawings of the
control equipment:
•

Overview drawing that shows the location of each PLC in relation to the process or machine.

•

Mechanical layout drawing of each PLC and any I/O modules, including any cabinets and
other equipment.

•

Electrical drawings for each PLC and any I/O modules, including the device model numbers,
communications addresses, and I/O addresses.

Create a list of symbolic names for the absolute addresses. Include not only the physical I/O
signals, but also the other elements (such as tag names) to be used in your program.

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7.2 Structuring your user program

7.2

Structuring your user program
When you create a user program for the automation tasks, you insert the instructions for the
program into code blocks:
● An organization block (OB) responds to a specific event in the CPU and can interrupt the
execution of the user program. The default for the cyclic execution of the user program
(OB 1) provides the base structure for your user program. If you include other OBs in your
program, these OBs interrupt the execution of OB 1. The other OBs perform specific
functions, such as for startup tasks, for handling interrupts and errors, or for executing
specific program code at specific time intervals.
● A function block (FB) is a subroutine that is executed when called from another code
block (OB, FB, or FC). The calling block passes parameters to the FB and also identifies
a specific data block (DB) that stores the data for the specific call or instance of that FB.
Changing the instance DB allows a generic FB to control the operation of a set of
devices. For example, one FB can control several pumps or valves, with different
instance DBs containing the specific operational parameters for each pump or valve.
● A function (FC) is a subroutine that is executed when called from another code block (OB,
FB, or FC). The FC does not have an associated instance DB. The calling block passes
parameters to the FC. The output values from the FC must be written to a memory
address or to a global DB.

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7.2 Structuring your user program

Choosing the type of structure for your user program
Based on the requirements of your application, you can choose either a linear structure or a
modular structure for creating your user program:
● A linear program executes all of the instructions for your automation tasks in sequence,
one after the other. Typically, the linear program puts all of the program instructions into
the OB for the cyclic execution of the program (OB 1).
● A modular program calls specific code blocks that perform specific tasks. To create a
modular structure, you divide the complex automation task into smaller subordinate tasks
that correspond to the technological functions of the process. Each code block provides
the program segment for each subordinate task. You structure your program by calling
one of the code blocks from another block.
Linear structure:

Modular structure:

By creating generic code blocks that can be reused within the user program, you can simplify
the design and implementation of the user program. Using generic code blocks has a
number of benefits:
● You can create reusable blocks of code for standard tasks, such as for controlling a pump
or a motor. You can also store these generic code blocks in a library that can be used by
different applications or solutions.
● When you structure the user program into modular components that relate to functional
tasks, the design of your program can be easier to understand and to manage. The
modular components not only help to standardize the program design, but can also help
to make updating or modifying the program code quicker and easier.
● Creating modular components simplifies the debugging of your program. By structuring
the complete program as a set of modular program segments, you can test the
functionality of each code block as it is developed.
● Creating modular components that relate to specific technological functions can help to
simplify and reduce the time involved with commissioning the completed application.

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7.3 Using blocks to structure your program

7.3

Using blocks to structure your program
By designing FBs and FCs to perform generic tasks, you create modular code blocks. You
then structure your program by having other code blocks call these reusable modules. The
calling block passes device-specific parameters to the called block.
When a code block calls another code block, the CPU executes the program code in the
called block. After execution of the called block is complete, the CPU resumes the execution
of the calling block. Processing continues with execution of the instruction that follows after
the block call.
A

Calling block

Called (or interrupting) block

① Program execution
② Instruction or event that initiates the execution of
another block

③ Program execution
④ Block end (returns to calling block)

You can nest the block calls for a more modular structure. In the following example, the
nesting depth is 3: the program cycle OB plus 3 layers of calls to code blocks.

①
②

Start of cycle
Nesting depth

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7.3 Using blocks to structure your program

7.3.1

Organization block (OB)
Organization blocks provide structure for your program. They serve as the interface between
the operating system and the user program. OBs are event driven. An event, such as a
diagnostic interrupt or a time interval, causes the CPU to execute an OB. Some OBs have
predefined start events and behavior.
The program cycle OB contains your main program. You can include more than one program
cycle OB in your user program. During RUN mode, the program cycle OBs execute at the
lowest priority level and can be interrupted by all other event types. The startup OB does not
interrupt the program cycle OB because the CPU executes the startup OB before going to
RUN mode.
After finishing the processing of the program cycle OBs, the CPU immediately executes the
program cycle OBs again. This cyclic processing is the "normal" type of processing used for
programmable logic controllers. For many applications, the entire user program is located in
a single program cycle OB.
You can create other OBs to perform specific functions, such as for handling interrupts and
errors, or for executing specific program code at specific time intervals. These OBs interrupt
the execution of the program cycle OBs.
Use the "Add new block" dialog to create new OBs in your user program.
Interrupt handling is always
event-driven. When such
an event occurs, the CPU
interrupts the execution of
the user program and calls
the OB that was configured
to handle that event. After
finishing the execution of
the interrupting OB, the
CPU resumes the execution of the user program at
the point of interruption.

The CPU determines the order for handling interrupt events by priority. You can assign
multiple interrupt events to the same priority class. For more information, refer to the topics
on organization blocks (Page 92) and execution of the user program (Page 83).

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Creating additional OBs
You can create multiple OBs for your user program, even for the program cycle and startup
OB events. Use the "Add new block" dialog to create an OB and enter a name for your OB.
If you create multiple program cycle OBs for your user program, the CPU executes each
program cycle OB in numerical sequence, starting with the program cycle OB with the lowest
number (such as OB 1). For example: after the first program cycle OB (such as OB 1)
finishes, the CPU executes the program cycle OB with the next higher number.

Configuring the properties of an OB
You can modify the properties of an OB. For example, you can configure the OB number or
programming language.

Note
Note that you can assign a process image part number to an OB that corresponds to PIP0,
PIP1, PIP2, PIP3, or PIP4. If you enter a number for the process image part number, the
CPU creates that process image partition. See the topic "Execution of the user program
(Page 83)" for an explanation of the process image partitions.

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7.3.2

Function (FC)
A function (FC) is a code block that typically performs a specific operation on a set of input
values. The FC stores the results of this operation in memory locations. For example, use
FCs to perform standard and reusable operations (such as for mathematical calculations) or
technological functions (such as for individual controls using bit logic operations). An FC can
also be called several times at different points in a program. This reuse simplifies the
programming of frequently recurring tasks.
An FC does not have an associated instance data block (DB). The FC uses the local data
stack for the temporary data used to calculate the operation. The temporary data is not
saved. To store data permanently, assign the output value to a global memory location, such
as M memory or to a global DB.

7.3.3

Function block (FB)
A function block (FB) is a code block that uses an instance data block for its parameters and
static data. FBs have variable memory that is located in a data block (DB), or "instance" DB.
The instance DB provides a block of memory that is associated with that instance (or call) of
the FB and stores data after the FB finishes. You can associate different instance DBs with
different calls of the FB. The instance DBs allow you to use one generic FB to control
multiple devices. You structure your program by having one code block make a call to an FB
and an instance DB. The CPU then executes the program code in that FB, and stores the
block parameters and the static local data in the instance DB. When the execution of the FB
finishes, the CPU returns to the code block that called the FB. The instance DB retains the
values for that instance of the FB. These values are available to subsequent calls to the
function block either in the same scan cycle or other scan cycles.

Reusable code blocks with associated memory
You typically use an FB to control the operation for tasks or devices that do not finish their
operation within one scan cycle. To store the operating parameters so that they can be
quickly accessed from one scan to the next, each FB in your user program has one or more
instance DBs. When you call an FB, you also specify an instance DB that contains the block
parameters and the static local data for that call or "instance" of the FB. The instance DB
maintains these values after the FB finishes execution.
By designing the FB for generic control tasks, you can reuse the FB for multiple devices by
selecting different instance DBs for different calls of the FB.
An FB stores the Input, Output, and InOut, and Static parameters in an instance DB.
You can also modify and download the function block interface in RUN mode (Page 1341).

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7.3 Using blocks to structure your program

Assigning the start value in the instance DB
The instance DB stores both a default value and a start value for each parameter. The start
value provides the value to be used when the FB is executed. The start value can then be
modified during the execution of your user program.
The FB interface also provides a "Default value" column that allows you to assign a new start
value for the parameter as you are writing the program code. This default value in the FB is
then transferred to the start value in the associated instance DB. If you do not assign a new
start value for a parameter in the FB interface, the default value from instance DB is copied
to start value.

Using a single FB with DBs
The following figure shows an OB that calls one FB three times, using a different data block
for each call. This structure allows one generic FB to control several similar devices, such as
motors, by assigning a different instance data block for each call for the different devices.
Each instance DB stores the data (such as speed, ramp-up time, and total operating time)
for an individual device.

In this example, FB 22 controls three separate devices, with DB 201 storing the operational
data for the first device, DB 202 storing the operational data for the second device, and DB
203 storing the operational data for the third device.

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7.3.4

Data block (DB)
You create data blocks (DB) in your user program to store data for the code blocks. All of the
program blocks in the user program can access the data in a global DB, but an instance DB
stores data for a specific function block (FB).
The data stored in a DB is not deleted when the execution of the associated code block
comes to an end. There are two types of DBs:
● A global DB stores data for the code blocks in your program. Any OB, FB, or FC can
access the data in a global DB.
● An instance DB stores the data for a specific FB. The structure of the data in an instance
DB reflects the parameters (Input, Output, and InOut) and the static data for the FB. (The
Temp memory for the FB is not stored in the instance DB.)
Note
Although the instance DB reflects the data for a specific FB, any code block can access
the data in an instance DB.
You can also modify and download data blocks in RUN mode (Page 1341).

Read-only data blocks
You can configure a DB as being read-only:
1. Right-click the DB in the project navigator and select "Properties" from the context menu.
2. In the "Properties" dialog, select "Attributes".
3. Select the "Data block write-protected in the device" option and click "OK".

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7.3 Using blocks to structure your program

Optimized and standard data blocks
You can also configure a data block to be either standard or optimized. A standard DB is
compatible with STEP 7 Classic programming tools and the classic S7-300 and S7-400
CPUs. Data blocks with optimized access have no fixed defined structure. The data
elements contain only a symbolic name in the declaration and no fixed address within the
block. The CPU stores the elements automatically in the available memory area of the block
so that there are no gaps in the memory. This makes for optimal use of the memory
capacity.
To set optimized access for a data block, follow these steps:
1. Expand the program blocks folder in the STEP 7 project tree.
2. Right-click the data block and select "Properties" from the context menu.
3. For the attributes, select "Optimized block access".
Note that optimized block access is the default for new data blocks. If you deselect
"Optimized block access", the block uses standard access.
Note
Block access type for an FB and its instance DB
Be sure that if your FB setting is "Optimized block access" then the setting of the instance
DB for that FB is also "Optimized block access". Similarly if you have not selected
"Optimized block access" for the FB such that the FB is of type standard access, then be
sure that the instance DB is also standard, or not optimized block access.
If you do not have compatible block access types, then changes to the IN/OUT parameter
values of the FB from an HMI during execution of the FB could be lost.

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7.3.5

Creating reusable code blocks
Use the "Add new block"
dialog under "Program
blocks" in the Project navigator to create OBs, FBs,
FCs, and global DBs.
When you create a code
block, you select the programming language for the
block. You do not select a
language for a DB because
it only stores data.
Selecting the "Add new
and open" check box (default) opens the code block
in the Project view.

You can store objects you want to reuse in libraries. For each project, there is a project
library that is connected to the project. In addition to the project library, you can create any
number of global libraries that can be used over several projects. Since the libraries are
compatible with each other, library elements can be copied and moved from one library to
another.
Libraries are used, for example, to create templates for blocks that you first paste into the
project library and then further develop there. Finally, you copy the blocks from the project
library to a global library. You make the global library available to other colleagues working
on your project. They use the blocks and further adapt them to their individual requirements,
where necessary.
For details about library operations, refer to the STEP 7 online Help library topics.

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7.3 Using blocks to structure your program

7.3.6

Passing parameters to blocks
Function Blocks (FB) and Functions (FC) have three different interface types:
● IN
● IN/OUT
● OUT
FBs and FCs receive parameters through the IN and IN/OUT interface types. The blocks
process the parameters and return values to the caller through the IN/OUT and OUT
interface types.
The user program transfers parameters using one of two methods.

Call-by-value
When the user program passes a parameter to a function as "call-by-value", the user
program copies the actual parameter value into the input parameter of the block for the IN
interface type. This operation requires additional memory for the copied value.

When the user program calls the block, it copies the values.

Call-by-reference
When the user program passes a parameter to a function as "call-by-reference", the user
program references the address of the actual parameter for the IN/OUT interface type and
does not copy the value. This operation does not require additional memory.

When the user program calls the block, it references the address of the actual parameters.
Note
Generally, use the IN/OUT interface type for structured tags (for example, ARRAY,
STRUCT, and STRING) in order to avoid increasing the required data memory
unnecessarily.

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Block optimization and passing parameters
The user program passes FC parameters as "call-by-value" for simple data types (for
example, INT, DINT, and REAL). It passes complex data types (for example, STRUCT,
ARRAY, and STRING) as "call-by-reference".
The user program normally passes FB parameters in the instance Data block (DB)
associated with the FB:
● The user program passes simple data types (for example, INT, DINT, and REAL) as "callby-value" by copying the parameters to/from the instance DB.
● The user program copies complex data types (for example, STRUCT, ARRAY, and
STRING) to and from the instance DB for IN and OUT parameter types.
● The user program passes complex data types as "call-by-reference" for the IN/OUT
interface type.
DBs can be created as either "Optimized" or "Standard" (non-optimized). The optimized data
blocks are more compact than the non-optimized data blocks. Also, the ordering of the data
elements within the DB is different for optimized versus non-optimized DBs. Refer to the
"Optimized blocks" section of the S7-Programming Guideline for S7-1200/1500, STEP 7 (TIA
Portal), 03/2014 (http://support.automation.siemens.com/WW/view/en/81318674) for a
discussion of optimized blocks.
You create FBs and FCs to process either optimized or non-optimized data. You can select
the "Optimized block access" check box as one of the attributes for the block. The user
program optimizes program blocks by default, and the program blocks expect data passed to
the block to be in the optimized format.
When the user program passes a complex parameter (for example, a STRUCT) to a
function, the system checks the optimization setting of the data block containing the structure
and the optimization setting of the program block. If you optimize both the data block and the
function, then the user program passes the STRUCT as a "call-by-reference". The same is
true if you select non-optimized for both the data block and the function.
However, if you make the function and data block optimization different (meaning that you
optimized one block and not the other block), the STRUCT must be converted to the format
expected by the function. For example, if you select non-optimized for the data block and
optimized for the function, then a STRUCT in the data block must be converted to an
optimized format before the function can process the STRUCT. The system does this
conversion by making a "copy" of the STRUCT and converting it to the optimized format that
the function expects.
In summary, when the user program passes a complex data type (for example, a STRUCT)
to a function as an IN/OUT parameter, the function expects the user program to pass the
STRUCT as a "call-by-reference":
● If you select optimized or non-optimized for both the data block containing the STRUCT
and the function, the user program passes the data as "call-by-reference".
● If you do not configure the data block and the function with the same optimization settings
(one is optimized and the other is non-optimized), the system must make a copy of the
STRUCT before passing it to the function. Because the system has to make this copy of
the structure, this converts the "call-by-reference", effectively, into a "call-by-value".

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Effect of optimization settings on user programs
The copying of the parameter can cause an issue in a user program if an HMI or interrupt
OB modifies elements of the structure. For example, there is an IN/OUT parameter of a
function (normally passed as "call-by-reference"), but the optimization settings of the data
block and function are different:
1. When the user program is ready to call the function, the system must make a "copy" of
the structure to change the format of the data to match the function.
2. The user program calls the function with a reference to the "copy" of the structure.
3. An interrupt OB occurs while the function is executing, and the interrupt OB changes a
value in the original structure.
4. The function completes and, since the structure is an IN/OUT parameter, the system
copies the values back to the original structure in the original format.
The effect of making the copy of the structure to change the format is that the data written by
the interrupt OB is lost. The same can happen when writing a value with an HMI. The HMI
can interrupt the user program and write a value in the same manner as an interrupt OB.
There are multiple ways to correct this issue:
● The best solution for this this issue is to match the optimization settings of the program
block and the data block when using complex data types (for example, a STRUCT). This
ensures that the user program always passes the parameters as "call-by-reference".
● Another solution is that an interrupt OB or HMI does not directly modify an element in the
structure. The OB or HMI can modify another variable, and then you can copy this
variable into the structure at a specific point in the user program.

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7.4 Understanding data consistency

7.4

Understanding data consistency
The CPU maintains the data consistency for all of the elementary data types (such as Words
or DWords) and all of the system-defined structures (for example, IEC_TIMERS or DTL).
The reading or writing of the value cannot be interrupted. (For example, the CPU protects
the access to a DWord value until the four bytes of the DWord have been read or written.) To
ensure that the program cycle OBs and the interrupt OBs cannot write to the same memory
location at the same time, the CPU does not execute an interrupt OB until the read or write
operation in the program cycle OB has been completed.
If your user program shares multiple values in memory between a program cycle OB and an
interrupt OB, your user program must also ensure that these values are modified or read
consistently. You can use the DIS_AIRT (disable alarm interrupt) and EN_AIRT (enable
alarm interrupt) instructions in your program cycle OB to protect any access to the shared
values.
● Insert a DIS_AIRT instruction in the code block to ensure that an interrupt OB cannot be
executed during the read or write operation.
● Insert the instructions that read or write the values that could be altered by an interrupt
OB.
● Insert an EN_AIRT instruction at the end of the sequence to cancel the DIS_AIRT and
allow the execution of the interrupt OB.
A communication request from an HMI device or another CPU can also interrupt execution of
the program cycle OB. The communication requests can also cause problems with data
consistency. The CPU ensures that the elementary data types are always read and written
consistently by the user program instructions. Because the user program is interrupted
periodically by communications, it is not possible to guarantee that multiple values in the
CPU will all be updated at the same time by the HMI. For example, the values displayed on a
given HMI screen could be from different scan cycles of the CPU.
The PtP (Point-to-Point) instructions, PROFINET instructions (such as TSEND_C and
TRCV_C), PROFINET Distributed I/O instructions (Page 384), and PROFIBUS Distributed
I/O Instructions (Page 384) transfer buffers of data that could be interrupted. Ensure the data
consistency for the buffers of data by avoiding any read or write operation to the buffers in
both the program cycle OB and an interrupt OB. If it is necessary to modify the buffer values
for these instructions in an interrupt OB, use a DIS_AIRT instruction to delay any interruption
(an interrupt OB or a communication interrupt from an HMI or another CPU) until an
EN_AIRT instruction is executed.
Note
The use of the DIS_AIRT instruction delays the processing of interrupt OBs until the
EN_AIRT instruction is executed, affecting the interrupt latency (time from an event to the
time when the interrupt OB is executed) of your user program.

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7.5 Programming language

7.5

Programming language
STEP 7 provides the following standard programming languages for S7-1200:
● LAD (ladder logic) is a graphical programming language. The representation is based on
circuit diagrams (Page 199).
● FBD (Function Block Diagram) is a programming language that is based on the graphical
logic symbols used in Boolean algebra (Page 200).
● SCL (structured control language) is a text-based, high-level programming language
(Page 201).
When you create a code block, you select the programming language to be used by that
block.
Your user program can utilize code blocks created in any or all of the programming
languages.

7.5.1

Ladder logic (LAD)
The elements of a circuit diagram, such as normally closed and normally open contacts, and
coils are linked to form networks.

To create the logic for complex operations, you can insert branches to create the logic for
parallel circuits. Parallel branches are opened downwards or are connected directly to the
power rail. You terminate the branches upwards.
LAD provides "box" instructions for a variety of functions, such as math, timer, counter, and
move.
STEP 7 does not limit the number of instructions (rows and columns) in a LAD network.
Note
Every LAD network must terminate with a coil or a box instruction.

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Consider the following rules when creating a LAD network:
● You cannot create a branch that could result in a power flow in the reverse direction.

● You cannot create a branch that would cause a short circuit.

7.5.2

Function Block Diagram (FBD)
Like LAD, FBD is also a graphical programming language. The representation of the logic is
based on the graphical logic symbols used in Boolean algebra.
To create the logic for complex operations,
insert parallel branches between the boxes.

Mathematical functions and other complex functions can be represented directly in
conjunction with the logic boxes.
STEP 7 does not limit the number of instructions (rows and columns) in an FBD network.

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7.5 Programming language

7.5.3

SCL
Structured Control Language (SCL) is a high-level, PASCAL-based programming language
for the SIMATIC S7 CPUs. SCL supports the block structure of STEP 7 (Page 187). Your
project can include program blocks in any of the three programming languages: SCL, LAD,
and FBD.
SCL instructions use standard programming operators, such as for assignment (:=),
mathematical functions (+ for addition, - for subtraction, * for multiplication, and / for division).
SCL also uses standard PASCAL program control operations, such as IF-THEN-ELSE,
CASE, REPEAT-UNTIL, GOTO and RETURN. You can use any PASCAL reference for
syntactical elements of the SCL programming language. Many of the other instructions for
SCL, such as timers and counters, match the LAD and FBD instructions. For more
information about specific instructions, refer to the specific instructions in the chapters for
Basic instructions (Page 227) and Extended instructions (Page 335).

7.5.3.1

SCL program editor
You can designate any type of block (OB, FB, or FC) to use the SCL programming language
at the time you create the block. STEP 7 provides an SCL program editor that includes the
following elements:
● Interface section for defining the parameters of the code block
● Code section for the program code
● Instruction tree that contains the SCL instructions supported by the CPU
You enter the SCL code for your instruction directly in the code section. The editor includes
buttons for common code constructs and comments. For more complex instructions, simply
drag the SCL instructions from the instruction tree and drop them into your program. You can
also use any text editor to create an SCL program and then import that file into STEP 7.

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In the Interface section of the SCL code block you can declare the following types of
parameters:
● Input, Output, InOut, and Ret_Val: These parameters define the input tags, output tags,
and return value for the code block. The tag name that you enter here is used locally
during the execution of the code block. You typically would not use the global tag name in
the tag table.
● Static (FBs only; the illustration above is for an FC): The code block uses static tags for
storage of static intermediate results in the instance data block. The block retains static
data until overwritten, which can be after several cycles. The names of the blocks, which
this block calls as multi-instance, are also stored in the static local data.
● Temp: These parameters are the temporary tags that are used during the execution of
the code block.
● Constant: These are named constant values for your code block.
If you call the SCL code block from another code block, the parameters of the SCL code
block appear as inputs or outputs.

In this example, the tags for "Start" and "On" (from the project tag table) correspond to
"StartStopSwitch" and "RunYesNo" in the declaration table of the SCL program.

7.5.3.2

SCL expressions and operations

Constructing an SCL expression
An SCL expression is a formula for calculating a value. The expression consists of operands
and operators (such as *, /, + or -). The operands can be tags, constants, or expressions.
The evaluation of the expression occurs in a certain order, which is defined by the following
factors:
● Every operator has a pre-defined priority, with the highest-priority operation performed
first.
● For operators with equal priority, the operators are processed in a left-to-right sequence.
● You use parentheses to designate a series of operators to be evaluated together.

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The result of an expression can be used either for assigning a value to a tag used by your
program, as a condition to be used by a control statement, or as parameters for another SCL
instruction or for calling a code block.
Table 7- 2

Operators in SCL

Type

Operation

Operator

Priority

Parentheses

(Expression)

(,)

Math

Comparison

Bit logic

Assignment

Power

Sign (unary plus)

Sign (unary minus)

Multiplication

Division

Modulo

MOD

Addition

Subtraction

Less than

Less than or equal to

Greater than

Greater than or equal to

Equal to

Not equal to

Negation (unary)

NOT

AND logic operation

AND or &

Exclusive OR logic operation

XOR

OR logic operation

Assignment

As a high-level programming language, SCL uses standard statements for basic tasks:
● Assignment statement: :=
● Mathematical functions: +, -, *, and /
● Addressing of global variables (tags): "" (Tag name or data block name
enclosed in double quotes)
● Addressing of local variables: # (Variable name preceded by "#" symbol)
The following examples show different expressions for different uses:
"C" := #A+#B;

"Data_block_1".Tag := #A;

IF #A > #B THEN "C" := #A;

"C" := SQRT (SQR (#A) + SQR (#B));

Assigns the sum of two local variables to a tag
Assignment to a data block tag
Condition for the IF-THEN statement
Parameters for the SQRT instruction

Arithmetic operators can process various numeric data types. The data type of the result is
determined by the data type of the most-significant operands. For example, a multiplication
operation that uses an INT operand and a REAL operand yields a REAL value for the result.

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Control statements
A control statement is a specialized type of SCL expression that performs the following
tasks:
● Program branching
● Repeating sections of the SCL program code
● Jumping to other parts of the SCL program
● Conditional execution
The SCL control statements include IF-THEN, CASE-OF, FOR-TO-DO, WHILE-DO,
REPEAT-UNTIL, CONTINUE, GOTO, and RETURN.
A single statement typically occupies one line of code. You can enter multiple statements on
one line, or you can break a statement into several lines of code to make the code easier to
read. Separators (such as tabs, line breaks and extra spaces) are ignored during the syntax
check. An END statement terminates the control statement.
The following examples show a FOR-TO-DO control statement. (Both forms of coding are
syntactically valid.)
FOR x := 0 TO max DO sum := sum + value(x); END_FOR;
FOR x := 0 TO max DO
sum := sum + value(x);
END_FOR;
A control statement can also be provided with a label. A label is set off by a colon at the
beginning of the statement:
Label: ;
The STEP 7 online help provides a complete SCL programming language reference.

Conditions
A condition is a comparison expression or a logical expression whose result is of type BOOL
(with the value of either TRUE or FALSE). The following example shows conditions of
various types:
#Temperature > 50
#Counter <= 100
#CHAR1 < 'S'
(#Alpha <> 12) AND NOT #Beta
5 + #Alpha

Relational expression
Comparison and logical expression
Arithmetic expression

A condition can use arithmetic expressions:
● The condition of the expression is TRUE if the result is any value other than zero.
● The condition of the expression is FALSE if the result equals zero.

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Calling other code blocks from your SCL program
To call another code block in your user program, simply enter the name (or absolute
address) of the FB or FC with the parameters. For an FB, you must provide the instance DB
to be called with the FB.
(Parameter list)

Call as a single instance

<#Instance name> (Parameter list)

"MyDB"(MyInput:=10, MyInOut:="Tag1");
(Parameter list)

:= (Parameter list)

"MyFC"(MyInput:=10, MyInOut:="Tag1");

Call as multi-instance
Standard call
Call in an expression

You can also drag blocks from the navigation tree to the SCL program editor, and complete
the parameter assignment.

Adding block comments to SCL code
You can include a block comment in your SCL code by including the comment text between
(* and *). You can have any number of comment lines between the (* and the *). Your SCL
program block can include many block comments. For programming convenience, the SCL
editor includes a block comment button along with common control statements:

Addressing
As with LAD and FBD, SCL allows you to use either tags (symbolic addressing) or absolute
addresses in your user program. SCL also allows you to use a variable as an array index.
Absolute addressing
%I0.0
%MB100

Precede absolute addresses with the "%" symbol.
Without the "%", STEP 7 generates an undefined
tag error at compile time.

Symbolic addressing
"PLC_Tag_1"

"Data_block_1".Tag_1

"Data_block_1".MyArray[#i]

Tag in PLC tag table
Tag in a data block
Array element in a data block array

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7.5.3.3

Indexed addressing with PEEK and POKE instructions
SCL provides PEEK and POKE instructions that allow you to read from or write to data
blocks, I/O, or memory. You provide parameters for specific byte offsets or bit offsets for the
operation.
Note
To use the PEEK and POKE instructions with data blocks, you must use standard (not
optimized) data blocks. Also note that the PEEK and POKE instructions merely transfer data.
They have no knowledge of data types at the addresses.

PEEK(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_);

Reads the byte referenced by byteOffset of
the referenced data block, I/O or memory
area.
Example referencing data block:

%MB100 := PEEK(area:=16#84,
dbNumber:=1, byteOffset:=#i);

Example referencing IB3 input:

PEEK_WORD(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_);

%MB100 := PEEK(area:=16#81,
dbNumber:=0, byteOffset:=#i); // when
#i = 3

Reads the word referenced by byteOffset of
the referenced data block, I/O or memory
area.
Example:

PEEK_DWORD(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_);

%MW200 := PEEK_WORD(area:=16#84,
dbNumber:=1, byteOffset:=#i);

Reads the double word referenced by
byteOffset of the referenced data block, I/O or
memory area.
Example:

PEEK_BOOL(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_,
bitOffset:=_in_);

%MD300 := PEEK_DWORD(area:=16#84,
dbNumber:=1, byteOffset:=#i);

Reads a Boolean referenced by the bitOffset
and byteOffset of the referenced data block,
I/O or memory area
Example:

%MB100.0 := PEEK_BOOL(area:=16#84,
dbNumber:=1, byteOffset:=#ii,
bitOffset:=#j);

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POKE(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_,
value:=_in_);

Writes the value (Byte, Word, or DWord) to
the referenced byteOffset of the referenced
data block, I/O or memory area
Example referencing data block:

POKE(area:=16#84, dbNumber:=2,
byteOffset:=3, value:="Tag_1");

Example referencing QB3 output:
POKE_BOOL(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_,
bitOffset:=_in_,
value:=_in_);

POKE_BLK(area_src:=_in_,
dbNumber_src:=_in_,
byteOffset_src:=_in_,
area_dest:=_in_,
dbNumber_dest:=_in_,
byteOffset_dest:=_in_,
count:=_in_);

POKE(area:=16#82, dbNumber:=0,
byteOffset:=3, value:="Tag_1");

Writes the Boolean value to the referenced
bitOffset and byteOffset of the referenced
data block, I/O or memory area
Example:

POKE_BOOL(area:=16#84, dbNumber:=2,
byteOffset:=3, bitOffset:=5, value:=0);

Writes "count" number of bytes starting at the
referenced byte Offset of the referenced
source data block, I/O or memory area to the
referenced byteOffset of the referenced destination data block, I/O or memory area
Example:

POKE_BLK(area_src:=16#84,
dbNumber_src:=#src_db, byteOffset_src:=#src_byte, area_dest:=16#84,
dbNumber_dest:=#src_db, byteOffset_dest:=#src_byte, count:=10);

For PEEK and POKE instructions, the following values for the "area", "area_src" and
"area_dest" parameters are applicable. For areas other than data blocks, the dbNumber
parameter must be 0.
16#81

16#82

16#83

16#84

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7.5.4

EN and ENO for LAD, FBD and SCL

Determining "power flow" (EN and ENO) for an instruction
Certain instructions (such as the Math and the Move instructions) provide parameters for EN
and ENO. These parameters relate to power flow in LAD or FBD and determine whether the
instruction is executed during that scan. SCL also allows you to set the ENO parameter for a
code block.
● EN (Enable In) is a Boolean input. Power flow (EN = 1) must be present at this input for
the box instruction to be executed. If the EN input of a LAD box is connected directly to
the left power rail, the instruction will always be executed.
● ENO (Enable Out) is a Boolean output. If the box has power flow at the EN input and the
box executes its function without error, then the ENO output passes power flow
(ENO = 1) to the next element. If an error is detected in the execution of the box
instruction, then power flow is terminated (ENO = 0) at the box instruction that generated
the error.
Table 7- 3

Operands for EN and ENO

Program editor

Inputs/outputs

Operands

Data type

LAD

EN, ENO

Power flow

Bool

FBD

I, I:P, Q, M, DB, Temp, Power Flow

Bool

ENO

Power Flow

Bool

EN1

TRUE, FALSE

Bool

ENO2

TRUE, FALSE

Bool

SCL
1

The use of EN is only available for FBs.

The use of ENO with the SCL code block is optional. You must configure the SCL compiler to set
ENO when the code block finishes.

Configuring SCL to set ENO
To configure the SCL compiler for setting ENO, follow these steps:
1. Select the "Settings" command from the "Options" menu.
2. Expand the "PLC programming" properties and select "SCL (Structured Control
Language)".
3. Select the "Set ENO automatically" option.

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Using ENO in program code
You can also use ENO in your program code, for example by assigning ENO to a PLC tag,
or by evaluating ENO in a local block.
Examples:
“MyFunction”
( IN1 := … ,
IN2 := … ,
OUT1 => #myOut,
ENO => #statusFlag ); // PLC tag statusFlag holds the value of E
NO
“MyFunction”
( IN1 := …
IN2 := … ,
OUT1 => #myOut,
ENO => ENO ); // block status flag of "MyFunction"
// is stored in the local block
IF ENO = TRUE THEN
// execute code only if MyFunction returns true ENO

Effect of Ret_Val or Status parameters on ENO
Some instructions, such as the communication instructions or the string conversion
instructions, provide an output parameter that contains information about the processing of
the instruction. For example, some instructions provide a Ret_Val (return value) parameter,
which is typically an Int data type that contains status information in a range from -32768 to
+32767. Other instructions provide a Status parameter, which is typically a Word data type
that stores status information in a range of hexadecimal values from 16#0000 to 16#FFFF.
The numerical value stored in a Ret_Val or a Status parameter determines the state of ENO
for that instruction.
● Ret_Val: A value from 0 to 32767 typically sets ENO = 1 (or TRUE). A value from -32768
to -1 typically sets ENO = 0 (or FALSE). To evaluate Ret_Val, change the representation
to hexadecimal.
● Status: A value from 16#0000 16#7FFF typically sets ENO = 1 (or TRUE). A value from
16#8000 to 16#FFFF typically sets ENO = 0 (or FALSE).
Instructions that take more than one scan to execute often provide a Busy parameter (Bool)
to signal that the instruction is active but has not completed execution. These instructions
often also provide a Done parameter (Bool) and an Error parameter (Bool). Done signals that
the instruction was completed without error, and Error signals that the instruction was
completed with an error condition.
● When Busy = 1 (or TRUE), ENO = 1 (or TRUE).
● When Done = 1 (or TRUE), ENO = 1 (or TRUE).
● When Error = 1 (or TRUE), ENO = 0 (or FALSE).

See also
OK (Check validity) and NOT_OK (Check invalidity) (Page 252)
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7.6 Protection

7.6

Protection

7.6.1

Access protection for the CPU
The CPU provides four levels of security for restricting access to specific functions. When
you configure the security level and password for a CPU, you limit the functions and memory
areas that can be accessed without entering a password.
Each level allows certain functions to be accessible without a password. The default
condition for the CPU is to have no restriction and no password-protection. To restrict access
to a CPU, you configure the properties of the CPU and enter the password.
Entering the password over a network does not compromise the password protection for the
CPU. Password protection does not apply to the execution of user program instructions
including communication functions. Entering the correct password provides access to all of
the functions at that level.
PLC-to-PLC communications (using communication instructions in the code blocks) are not
restricted by the security level in the CPU.
Table 7- 4

Security levels for the CPU

Security level

Access restrictions

Full access (no
protection)

Allows full access without password protection.

Read access

Allows HMI access, comparing Offline/Online code blocks, and all forms of PLCto-PLC communications without password protection.
Password is required for modifying (writing to) the CPU. Password is not required for changing the CPU mode (RUN/STOP).

HMI access

Allows HMI access and all forms of PLC-to-PLC communications without password protection.
Password is required for reading the data in the CPU, for comparing Offline/Online code blocks, for modifying (writing to) the CPU, and for changing the
CPU mode (RUN/STOP).

No access (complete protection)

Allows no access without password protection.
Password is required for HMI access, reading the data in the CPU, comparing
Offline/Online code blocks, and for modifying (writing to) the CPU.

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Passwords are case-sensitive. To configure the protection level and passwords, follow these
steps:
1. In the "Device configuration", select the CPU.
2. In the inspector window, select the "Properties" tab.
3. Select the "Protection" property to select the protection level and to enter passwords.

When you download this configuration to the CPU, the user has HMI access and can access
HMI functions without a password. To read data or compare Offline/Online code blocks, the
user must enter the configured password for "Read access" or the password for "Full access
(no protection)". To write data, the user must enter the configured password for "Full access
(no protection)".
WARNING
Unauthorized access to a protected CPU
Users with CPU full access privileges have privileges to read and write PLC variables.
Regardless of the access level for the CPU, Web server users can have privileges to read
and write PLC variables. Unauthorized access to the CPU or changing PLC variables to
invalid values could disrupt process operation and could result in death, severe personal
injury and/or property damage.
Authorized users can perform operating mode changes, writes to PLC data, and firmware
updates. Siemens recommends that you observe the following security practices:
• Password protect CPU access levels and Web server user IDs (Page 1005) with strong
passwords. Strong passwords are at least ten characters in length, mix letters, numbers,
and special characters, are not words that can be found in a dictionary, and are not
names or identifiers that can be derived from personal information. Keep the password
secret and change it frequently.
• Enable access to the Web server only with the HTTPS protocol.
• Do not extend the default minimum privileges of the Web server "Everybody" user.
• Perform error-checking and range-checking on your variables in your program logic
because Web page users can change PLC variables to invalid values.

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Connection mechanisms
To access remote connection partners with PUT/GET instructions, the user must also have
permission.
By default, the "Permit access with PUT/GET communication" option is not enabled. In this
case, read and write access to CPU data is only possible for communication connections
that require configuration or programming both for the local CPU and for the communication
partner. Access through BSEND/BRCV instructions is possible, for example.
Connections for which the local CPU is only a server (meaning that no
configuration/programming of the communication with the communication partner exists at
the local CPU), are therefore not possible during operation of the CPU, for example:
● PUT/GET, FETCH/WRITE or FTP access through communication modules
● PUT/GET access from other S7 CPUs
● HMI access through PUT/GET communication
If you want to allow access to CPU data from the client side, that is, you do not want to
restrict the communication services of the CPU, follow these steps:
1. Configure the protection access level to be any level other than "No access (complete
protection)".
2. Select the "Permit access with PUT/GET communication" check box.

When you download this configuration to the CPU, the CPU permits PUT/GET
communication from remote partners

7.6.2

External load memory
You can also protect the external load memory (memory card) from copies. To prevent the
copying of internal load memory to external load memory follow these steps:
1. From the device configuration of the CPU in STEP 7, select "Protection" from the General
properties.
2. In the "External Load Memory" section, select "Disable copy from internal load memory to
external load memory".
See also the topic Inserting a memory card in the CPU (Page 139) for a description of how
this property affects the insertion of a memory card into the CPU.

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7.6.3

Know-how protection
Know-how protection allows you to prevent one or more code blocks (OB, FB, FC, or DB) in
your program from unauthorized access. You create a password to limit access to the code
block. The password-protection prevents unauthorized reading or modification of the code
block. Without the password, you can read only the following information about the code
block:
● Block title, block comment, and block properties
● Transfer parameters (IN, OUT, IN_OUT, Return)
● Call structure of the program
● Global tags in the cross references (without information on the point of use), but local
tags are hidden
When you configure a block for "know-how" protection, the code within the block cannot be
accessed except after entering the password.
Use the "Properties" task card of the code block to configure the know-how protection for
that block. After opening the code block, select "Protection" from Properties.

1. In the Properties for the code block, click
the "Protection" button to display the
"Know-how protection" dialog.
2. Click the "Define" button to enter the
password.

After entering and confirming the password,
click "OK".

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7.6.4

Copy protection
An additional security feature allows you to bind program blocks for use with a specific
memory card or CPU. This feature is especially useful for protecting your intellectual
property. When you bind a program block to a specific device, you restrict the program or
code block for use only with a specific memory card or CPU. This feature allows you to
distribute a program or code block electronically (such as over the Internet or through email)
or by sending a memory card. Copy protection is available for OBs (Page 188), FBs
(Page 190), and FCs (Page 190). The S7-1200 CPU supports three types of block
protection:
● Binding to the serial number of a CPU
● Binding to the serial number of a memory card
● Dynamic binding with mandatory password
Use the "Properties" task card of the code block to bind the block to a specific CPU or
memory card.
1. After opening the code block, select "Protection".

2. From the drop-down list under "Copy protection" task, select the type of copy protection
that you want to use.

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3. For binding to the serial number of a CPU or memory card, select either to insert the
serial number when downloading, or enter the serial number for the memory card or
CPU.
Note
The serial number is case-sensitive.
For dynamic binding with mandatory password, define the password that you must use to
download or copy the block.
When you subsequently download (Page 216) a block with dynamic binding, you must
enter the password to be able to download the block. Note that the copy protection
password and the know-how protection (Page 213) password are two separate
passwords.

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7.7 Downloading the elements of your program

7.7

Downloading the elements of your program
You can download the elements of your project from the programming device to the CPU.
When you download a project, the CPU stores the user program (OBs, FCs, FBs and DBs)
in internal load memory or if a SIMATIC memory card is present in external load memory
(the card).

You can download your project from the programming device to your CPU from any of the
following locations:
● Project tree: Right-click the program element, and then click the context-sensitive
"Download" selection.
● Online menu: Click the "Download to device" selection.
● Toolbar: Click the "Download to device" icon.
● Device configuration: Right-click the CPU and select the elements to download.
Note that if you have applied dynamic binding with mandatory password (Page 214) to any
of the program blocks, you must enter the password for the protected blocks in order to
download them. If you have configured this type of copy protection for multiple blocks, you
must enter the password for each of the protected blocks in order to download them.
Note
Downloading a program does not clear or make any changes to existing values in retentive
memory. If you want to clear retentive memory before a download, then reset your CPU to
factory settings prior to downloading the program.
You can also download a panel project for the Basic HMI panels (Page 32) from the
TIA Portal to a memory card in the S7-1200 CPU.

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Downloading when the configured CPU is different from the connected CPU
STEP 7 and the S7-1200 permit a download if the connected CPU has the capacity to store
a download from the configured CPU, based on the memory requirements of the project and
the compatibility of the I/O. You can download the configuration and program from a CPU to
a larger CPU, for example, from a CPU 1211C DC/DC/DC to a CPU 1215C DC/DC/DC
because the I/O is compatible and the memory is sufficient. In this case, the download
operation displays a warning, "Differences between configured and target modules (online)"
along with the article numbers and firmware versions in the "Load preview" dialog. You must
choose either "No action" if you do not want the download to proceed or "Accept all" if you
do want the download to proceed:

Note
When you go online (Page 1313) after downloading the configured CPU to a different
connected CPU, you see the project for the configured CPU with online status indicators in
the project tree. In the online and diagnostics view, however, you see the actual connected
CPU module type.

Figure 7-1

Online view when configured CPU is different from connected CPU

You can, of course, change your device (Page 170) in the device configuration so that the
configured CPU is the same module type as the connected CPU. The "Change device"
dialog provides complete compatibility details when you try to change a device.

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7.7 Downloading the elements of your program
STEP 7 and the S7-1200 prohibit a download if the connected CPU does not have the
capacity to store a download from the configured CPU; for example, you cannot download
the hardware configuration and program for the following cases:
● CPU 1215C DC/DC/DC to a CPU 1212C DC/DC/DC due to insufficient work memory
● CPU 1211C DC/DC/Relay to a CPU 1211C DC/DC/DC due to I/O differences
● CPU 1217C DC/DC/DC to any CPU 1211C, CPU 1212C, CPU 1214C, or CPU 1215C
due to the 1.5 V DC outputs in the CPU 1217C.
● CPU 1214C V4.2 to CPU 1214C V4.0, due to firmware version incompatibility
The "Load preview" dialog displays an error in such cases:

Recovering from a failed download
If the download fails, the Info tab of the Inspector Window displays the reason. The
diagnostic buffer also provides information. After a failed download, follow these steps to be
able to download successfully:
1. Correct the problem as described in the error message.
2. Reattempt the download.
In rare cases, the download succeeds but a subsequent power cycle of the CPU fails. In this
case you may see an error in the diagnostic buffer such as:
● 16# 02:4175 -- CPU error: Memory card evaluation error: Unknown or incompatible
version of CPU configuration description current card type: No memory card Function
finished/aborted, new startup inhibit set: ..- Memory card missing, wrong type, wrong
content or protected
If this occurs and additional attempts to download fail, you must clear the internal load
memory or external load memory:
1. If using internal load memory, reset the CPU to factory settings.
2. If using a SIMATIC memory card, remove it and delete the contents of the memory card
(Page 145) before reinserting.
3. Download the hardware configuration and software.

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7.8 Synchronizing the online CPU and offline project

See also
Synchronizing the online CPU and offline project (Page 219)

7.8

Synchronizing the online CPU and offline project
When you download project blocks to the CPU, the CPU can detect whether blocks or tags
have changed in the online CPU since the last download. In such cases, the CPU offers you
the choice to synchronize the changes. This means that you can upload the online CPU
changes to the project before downloading the project to the CPU. Changes in the online
CPU can be due to a variety of factors:
● Changes to the start values of data block tags during runtime, for example by the
WRIT_DBL instruction (Page 538) or by loading a recipe
● A download from a "secondary" project (a project other than the one that originated the
last download) where one or more of the following conditions exist:
– The online CPU includes program blocks that do not exist in the project.
– Data block tags or block attributes differ between the offline project and online CPU.
– PLC tags exist in the online CPU that do not exist in the offline project.
Note
If you edit blocks or tags in the project that you used for the last download, you do not have
to make any choices about synchronization. STEP 7 and the CPU detect that the offline
project changes are newer than the online CPU and proceeds with a normal download
operation.

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7.8 Synchronizing the online CPU and offline project

Synchronization choices
When you download a project to the CPU, you see the synchronization dialog if STEP 7
detects that data blocks or tags in the online CPU are newer than the project values. For
example, if the STEP 7 program has executed WRIT_DBL and changed a start value for a
tag in Data_block_1, STEP 7 displays the following synchronization dialog when you initiate
a download:

This dialog lists the program blocks where differences exist. From this dialog, you have the
following choices:
● Online/offline comparison: If you click this button, STEP 7 displays the program blocks,
system blocks, technology objects, PLC tags, and PLC data types for the project as
compared to the online CPU (Page 1323). For each object, you can click to see a
detailed analysis of the differences including time stamps. You can use this information to
decide what to do about the differences between the online CPU and the project.
● Synchronize: If you click this button, STEP 7 uploads the data blocks, tags, and other
objects from the online CPU to the project. You can then continue with the program
download, unless program execution has again caused the project to be out of sync with
the CPU.
● Continue without synchronization: If you click this button, STEP 7 downloads the project
to the CPU.
● Cancel: If you click this button, you cancel the download operation.

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7.9 Uploading from the online CPU

7.9

Uploading from the online CPU
You can also copy the program blocks from an online CPU or a memory card attached to
your programming device.
Prepare the offline project for the copied program blocks:
1. Add a CPU device that matches the online CPU.
2. Expand the CPU node once so that the "Program
blocks" folder is visible.

To upload the program blocks from the online CPU to the
offline project, follow these steps:
1. Click the "Program blocks" folder in the offline project.
2. Click the "Go online" button.
3. Click the "Upload" button.
4. Confirm your decision from the Upload dialog
(Page 1313).
When the upload is complete, STEP 7 displays all of the
uploaded program blocks in the project.

7.9.1

Comparing the online CPU to the offline CPU
You can use the "Compare" editor (Page 1323) in STEP 7 to find differences between the
online and offline projects. You might find this useful prior to uploading from the CPU.

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7.10 Debugging and testing the program

7.10

Debugging and testing the program

7.10.1

Monitor and modify data in the CPU
As shown in the following table, you can monitor and modify values in the online CPU.
Table 7- 5

Monitoring and modifying data with STEP 7

Editor

Monitor

Modify

Force

Watch table

Yes

Force table

Yes

Program editor

Yes

Tag table

Yes

DB editor

Yes

Monitoring with a
watch table

Monitoring with the LAD editor

Refer to the "Online and diagnostics" chapter for more information about monitoring and
modifying data in the CPU (Page 1325).

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7.10 Debugging and testing the program

7.10.2

Watch tables and force tables
You use "watch tables" for monitoring and modifying the values of a user program being
executed by the online CPU. You can create and save different watch tables in your project
to support a variety of test environments. This allows you to reproduce tests during
commissioning or for service and maintenance purposes.
With a watch table, you can monitor and interact with the CPU as it executes the user
program. You can display or change values not only for the tags of the code blocks and data
blocks, but also for the memory areas of the CPU, including the inputs and outputs (I and Q),
peripheral inputs (I:P), bit memory (M), and data blocks (DB).
With the watch table, you can enable the physical outputs (Q:P) of a CPU in STOP mode.
For example, you can assign specific values to the outputs when testing the wiring for the
CPU.
STEP 7 also provides a force table for "forcing" a tag to a specific value. For more
information about forcing, see the section on forcing values in the CPU (Page 1333) in the
"Online and Diagnostics" chapter.
Note
The force values are stored in the CPU and not in the watch table.
You cannot force an input (or "I" address). However, you can force a peripheral input. To
force a peripheral input, append a ":P" to the address (for example: "On:P").
STEP 7 also provides the capability of tracing and recording program variables based on
trigger conditions (Page 1347).

7.10.3

Cross reference to show usage
The Inspector window displays cross-reference information about how a selected object is
used throughout the complete project, such as the user program, the CPU and any HMI
devices. The "Cross-reference" tab displays the instances where a selected object is being
used and the other objects using it. The Inspector window also includes blocks which are
only available online in the cross-references. To display the cross-references, select the
"Show cross-references" command. (In the Project view, find the cross references in the
"Tools" menu.)
Note
You do not have to close the editor to see the cross-reference information.

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You can sort the entries in the cross-reference. The cross-reference list provides an
overview of the use of memory addresses and tags within the user program.
● When creating and changing a program, you retain an overview of the operands, tags
and block calls you have used.
● From the cross-references, you can jump directly to the point of use of operands and
tags.
● During a program test or when troubleshooting, you are notified about which memory
location is being processed by which command in which block, which tag is being used in
which screen, and which block is called by which other block.
Table 7- 6

Elements of the cross reference

Column

Description

Object

Name of the object that uses the lower-level objects or that is being used by the
lower-level objects

Number

Number of uses

Point of use

Each location of use, for example, network

Property

Special properties of referenced objects, for example, the tag names in multiinstance declarations

Shows additional information about the object, such as whether an instance DB is
used as template or as a multiple instance

Access

Type of access, whether access to the operand is read access (R) and/or write
access (W)

Address

Address of the operand

Type

Information on the type and language used to create the object

Path

Path of object in project tree

Depending on the installed products, the cross-reference table displays additional or different
columns.

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7.10 Debugging and testing the program

7.10.4

Call structure to examine the calling hierarchy
The call structure describes the call hierarchy of the block within your user program. It
provides an overview of the blocks used, calls to other blocks, the relationships between
blocks, the data requirements for each block, and the status of the blocks. You can open the
program editor and edit blocks from the call structure.
Displaying the call structure provides you with a list of the blocks used in the user program.
STEP 7 highlights the first level of the call structure and displays any blocks that are not
called by any other block in the program. The first level of the call structure displays the OBs
and any FCs, FBs, and DBs that are not called by an OB. If a code block calls another block,
the called block is shown as an indentation under the calling block. The call structure only
displays those blocks that are called by a code block.
You can selectively display only the blocks causing conflicts within the call structure. The
following conditions cause conflicts:
● Blocks that execute any calls with older or newer code time stamps
● Blocks that call a block with modified interface
● Blocks that use a tag with modified address and/or data type
● Blocks that are called neither directly nor indirectly by an OB
● Blocks that call a non-existent or missing block
You can group several block calls and data blocks as a group. You use a drop-down list to
see the links to the various call locations.
You can also perform a consistency check to show time stamp conflicts. Changing the time
stamp of a block during or after the program is generated can lead to time stamp conflicts,
which in turn cause inconsistencies among the blocks that are calling and being called.
● Most time stamp and interface conflicts can be corrected by recompiling the code blocks.
● If compilation fails to clear up inconsistencies, use the link in the "Details" column to go to
the source of the problem in the program editor. You can then manually eliminate any
inconsistencies.
● Any blocks marked in red must be recompiled.

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8.1

Bit logic operations

8.1.1

Bit logic instructions
LAD and FBD are very effective for handling Boolean logic. While SCL is especially effective
for complex mathematical computation and for project control structures, you can use SCL
for Boolean logic.

LAD contacts
Table 8- 1
LAD

Table 8- 2

Normally open and normally closed contacts
SCL
IF in THEN
Statement;
ELSE
Statement;
END_IF;
IF NOT (in) THEN
Statement;
ELSE
Statement;
END_IF;

Description
Normally open and normally closed contacts: You can connect contacts
to other contacts and create your own combination logic. If the input bit
you specify uses memory identifier I (input) or Q (output), then the bit
value is read from the process-image register. The physical contact signals in your control process are wired to I terminals on the PLC. The CPU
scans the wired input signals and continuously updates the corresponding state values in the process-image input register.
You can perform an immediate read of a physical input using ":P" following the I offset (example: "%I3.4:P"). For an immediate read, the bit data
values are read directly from the physical input instead of the process
image. An immediate read does not update the process image.

Data types for the parameters

Parameter

Data type

Description

Bool

Assigned bit

● The Normally Open contact is closed (ON) when the assigned bit value is equal to 1.
● The Normally Closed contact is closed (ON) when the assigned bit value is equal to 0.
● Contacts connected in series create AND logic networks.
● Contacts connected in parallel create OR logic networks.

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FBD AND, OR, and XOR boxes
In FBD programming, LAD contact networks are transformed into AND (&), OR (>=1), and
EXCLUSIVE OR (x) box networks where you can specify bit values for the box inputs and
outputs. You may also connect to other logic boxes and create your own logic combinations.
After the box is placed in your network, you can drag the "Insert input" tool from the
"Favorites" toolbar or instruction tree and then drop it onto the input side of the box to add
more inputs. You can also right-click on the box input connector and select "Insert input".
Box inputs and outputs can be connected to another logic box, or you can enter a bit
address or bit symbol name for an unconnected input. When the box instruction is executed,
the current input states are applied to the binary box logic and, if true, the box output will be
true.
Table 8- 3
FBD

AND, OR, and XOR boxes
SCL1
out := in1 AND
in2;

Description

out := in1 OR in2;

Any input of an OR box must be TRUE for the output to be
TRUE.

out := in1 XOR
in2;

An odd number of the inputs of an XOR box must be TRUE for
the output to be TRUE.

All inputs of an AND box must be TRUE for the output to be
TRUE.

For SCL: You must assign the result of the operation to a variable to be used for another statement.

Table 8- 4

Data types for the parameters

Parameter

Data type

Description

IN1, IN2

Bool

Input bit

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NOT logic inverter
Table 8- 5
LAD

Invert RLO (Result of Logic Operation)
FBD

SCL
NOT

Description
For FBD programming, you can drag the "Invert RLO" tool
from the "Favorites" toolbar or instruction tree and then drop
it on an input or output to create a logic inverter on that box
connector.
The LAD NOT contact inverts the logical state of power flow
input.
•

If there is no power flow into the NOT contact, then there
is power flow out.

•

If there is power flow into the NOT contact, then there is
no power flow out.

Output coil and assignment box
The coil output instruction writes a value for an output bit. If the output bit you specify uses
memory identifier Q, then the CPU turns the output bit in the process-image register on or
off, setting the specified bit equal to power flow status. The output signals for your control
actuators are wired to the Q terminals of the CPU. In RUN mode, the CPU system
continuously scans your input signals, processes the input states according to your program
logic, and then reacts by setting new output state values in the process-image output
register. The CPU system transfers the new output state reaction that is stored in the
process-image register, to the wired output terminals.
Table 8- 6
LAD

Assignment and negate assignment
FBD

SCL
out := ;
out := NOT ;

Description
In FBD programming, LAD coils are transformed into
assignment (= and /=) boxes where you specify a bit address for the box output. Box inputs and outputs can be
connected to other box logic or you can enter a bit address.
You can specify an immediate write of a physical output
using ":P" following the Q offset (example: "%Q3.4:P").
For an immediate write, the bit data values are written to
the process image output and directly to physical output.

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Table 8- 7

Data types for the parameters

Parameter

Data type

Description

OUT

Bool

Assigned bit

● If there is power flow through an output coil or an FBD "=" box is enabled, then the output
bit is set to 1.
● If there is no power flow through an output coil or an FBD "=" assignment box is not
enabled, then the output bit is set to 0.
● If there is power flow through an inverted output coil or an FBD "/=" box is enabled, then
the output bit is set to 0.
● If there is no power flow through an inverted output coil or an FBD "/=" box is not enabled,
then the output bit is set to 1.

8.1.2

Set and reset instructions

Set and Reset 1 bit
Table 8- 8
LAD

S and R instructions
FBD

SCL

Description

Not available

Set output:
When S (Set) is activated, then the data value at the OUT
address is set to 1. When S is not activated, OUT is not
changed.

Not available

Reset output:
When R (Reset) is activated, then the data value at the OUT
address is set to 0. When R is not activated, OUT is not
changed.

For LAD and FBD: These instructions can be placed anywhere in the network.

For SCL: You must write code to replicate this function within your application.

Table 8- 9

Data types for the parameters

Parameter

Data type

Description

IN (or connect to contact/gate logic)

Bool

Bit tag of location to be monitored

OUT

Bool

Bit tag of location to be set or reset

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Set and Reset Bit Field
Table 8- 10
LAD1

SET_BF and RESET_BF instructions
FBD

SCL

Description

Not available

Set bit field:
When SET_BF is activated, a data value of 1 is assigned to "n"
bits starting at address tag OUT. When SET_BF is not activated, OUT is not changed.

Not available

Reset bit field:
RESET_BF writes a data value of 0 to "n" bits starting at address tag OUT. When RESET_BF is not activated, OUT is not
changed.

For LAD and FBD: These instructions must be the right-most instruction in a branch.

For SCL: You must write code to replicate this function within your application.

Table 8- 11

Data types for the parameters

Parameter

Data type

Description

OUT

Bool

Starting element of a bit field to be set or reset (Example:
#MyArray[3])

Constant (UInt)

Number of bits to write

Set-dominant and Reset-dominant flip-flops
Table 8- 12
LAD / FBD

RS and SR instructions
SCL

Description

Not available

Reset/set flip-flop:
RS is a set dominant latch where the set dominates. If the set (S1) and reset (R)
signals are both true, the value at address INOUT will be 1.

Not available

Set/reset flip-flop:
SR is a reset dominant latch where the reset dominates. If the set (S) and reset
(R1) signals are both true, the value at address INOUT will be 0.

For LAD and FBD: These instructions must be the right-most instruction in a branch.

For SCL: You must write code to replicate this function within your application.

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Table 8- 13

Data types for the parameters

Parameter

Data type

Description

S, S1

Bool

Set input; 1 indicates dominance

R, R1

Bool

Reset input; 1 indicates dominance

INOUT

Bool

Assigned bit tag "INOUT"

Bool

Follows state of "INOUT" bit

The "INOUT" tag assigns the bit address that is set or reset. The optional output Q follows
the signal state of the "INOUT" address.
Instruction
RS

"INOUT" bit

Previous state

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8.1.3
Table 8- 14
LAD

Positive and negative edge instructions
Positive and negative transition detection
FBD

SCL
Not available

Description
1

Scan operand for positive signal edge.
LAD: The state of this contact is TRUE when a positive transition (OFFto-ON) is detected on the assigned "IN" bit. The contact logic state is
then combined with the power flow in state to set the power flow out
state. The P contact can be located anywhere in the network except the
end of a branch.
FBD: The output logic state is TRUE when a positive transition (OFFto-ON) is detected on the assigned input bit. The P box can only be
located at the beginning of a branch.

Not available 1

Scan operand for negative signal edge.
LAD: The state of this contact is TRUE when a negative transition (ONto-OFF) is detected on the assigned input bit. The contact logic state is
then combined with the power flow in state to set the power flow out
state. The N contact can be located anywhere in the network except
the end of a branch.
FBD: The output logic state is TRUE when a negative transition (ON-toOFF) is detected on the assigned input bit. The N box can only be
located at the beginning of a branch.

Not available 1

Set operand on positve signal edge.
LAD: The assigned bit "OUT" is TRUE when a positive transition (OFFto-ON) is detected on the power flow entering the coil. The power flow
in state always passes through the coil as the power flow out state. The
P coil can be located anywhere in the network.
FBD: The assigned bit "OUT" is TRUE when a positive transition (OFFto-ON) is detected on the logic state at the box input connection or on
the input bit assignment if the box is located at the start of a branch.
The input logic state always passes through the box as the output logic
state. The P= box can be located anywhere in the branch.

Not available 1

Set operand on negative signal edge.
LAD: The assigned bit "OUT" is TRUE when a negative transition (ONto-OFF) is detected on the power flow entering the coil. The power flow
in state always passes through the coil as the power flow out state. The
N coil can be located anywhere in the network.
FBD: The assigned bit "OUT" is TRUE when a negative transition (ONto-OFF) is detected on the logic state at the box input connection or on
the input bit assignment if the box is located at the start of a branch.
The input logic state always passes through the box as the output logic
state. The N= box can be located anywhere in the branch.

For SCL: You must write code to replicate this function within your application.

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Table 8- 15
LAD / FBD

P_TRIG and N_TRIG
SCL
Not available

Description
1

Scan RLO (result of logic operation) for positve signal edge.
The Q output power flow or logic state is TRUE when a positive transition (OFF-to-ON) is detected on the CLK input state (FBD) or CLK power flow in (LAD).
In LAD, the P_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the P_TRIG instruction can be located anywhere except the end of a branch.

Not available 1

Scan RLO for negative signal edge.
The Q output power flow or logic state is TRUE when a negative transition (ON-to-OFF) is detected on the CLK input state (FBD) or CLK power flow in (LAD).
In LAD, the N_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the N_TRIG instruction can be located anywhere except the end of a branch.

For SCL: You must write code to replicate this function within your application.

Table 8- 16
LAD / FBD

R_TRIG and F_TRIG instructions
SCL
"R_TRIG_DB"(
CLK:=_in_,
Q=> _bool_out_);

Description
Set tag on positive signal edge.
The assigned instance DB is used to store the previous state of the CLK
input. The Q output power flow or logic state is TRUE when a positive
transition (OFF-to-ON) is detected on the CLK input state (FBD) or CLK
power flow in (LAD).
In LAD, the R_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the R_TRIG instruction can be located anywhere except the end of a branch.

"F_TRIG_DB"(
CLK:=_in_,
Q=> _bool_out_);

Set tag on negative signal edge.
The assigned instance DB is used to store the previous state of the CLK
input. The Q output power flow or logic state is TRUE when a negative
transition (ON-to-OFF) is detected on the CLK input state (FBD) or CLK
power flow in (LAD).
In LAD, the F_TRIG instruction cannot be located at the beginning or
end of a network. In FBD, the F_TRIG instruction can be located anywhere except the end of a branch.

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For R_TRIG and F_TRIG, when you insert the instruction in the program, the "Call options"
dialog opens automatically. In this dialog you can assign
whether the edge memory bit is stored in its own data block (single instance) or as a local
tag (multiple instance) in the
block interface. If you create a separate data block, you will find it in the project tree in the
"Program resources" folder
under "Program blocks > System blocks".
Table 8- 17

Data types for the parameters (P and N contacts/coils, P=, N=, P_TRIG and N_TRIG)

Parameter

Data type

Description

M_BIT

Bool

Memory bit in which the previous state of the input is saved

Bool

Input bit whose transition edge is detected

OUT

Bool

Output bit which indicates a transition edge was detected

CLK

Bool

Power flow or input bit whose transition edge is detected

Bool

Output which indicates an edge was detected

All edge instructions use a memory bit (M_BIT: P/N contacts/coils, P_TRIG/N_TRIG) or
(instance DB bit: R_TRIG, F_TRIG) to store the previous state of the monitored input signal.
An edge is detected by comparing the state of the input with the previous state. If the states
indicate a change of the input in the direction of interest, then an edge is reported by writing
the output TRUE. Otherwise, the output is written to FALSE.
Note
Edge instructions evaluate the input and memory-bit values each time they are executed,
including the first execution. You must account for the initial states of the input and memory
bit in your program design either to allow or to avoid edge detection on the first scan.
Because the memory bit must be maintained from one execution to the next, you should use
a unique bit for each edge instruction, and you should not use this bit any other place in your
program. You should also avoid temporary memory and memory that can be affected by
other system functions, such as an I/O update. Use only M, global DB, or Static memory (in
an instance DB) for M_BIT memory assignments.

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8.2 Timer operations

8.2

Timer operations
You use the timer instructions to create programmed time delays. The number of timers that
you can use in your user program is limited only by the amount of memory in the CPU. Each
timer uses a 16 byte IEC_Timer data type DB structure to store timer data that is specified at
the top of the box or coil instruction. STEP 7 automatically creates the DB when you insert
the instruction.

Table 8- 18

Timer instructions

LAD / FBD boxes

FBD only:

LAD coils

SCL
"IEC_Timer_0_DB".TP(
IN:=_bool_in_,
PT:=_time_in_,
Q=>_bool_out_,
ET=>_time_out_);

Description
The TP timer generates a pulse with a preset
width time.

"IEC_Timer_0_DB".TON (
IN:=_bool_in_,
PT:=_time_in_,
Q=>_bool_out_,
ET=>_time_out_);

The TON timer sets output Q to ON after a preset
time delay.

"IEC_Timer_0_DB".TOF (
IN:=_bool_in_,
PT:=_time_in_,
Q=>_bool_out_,
ET=>_time_out_);

The TOF timer resets output Q to OFF after a
preset time delay.

"IEC_Timer_0_DB".TONR (
IN:=_bool_in_,
R:=_bool_in_,
PT:=_time_in_,
Q=>_bool_out_,
ET=>_time_out_);

The TONR timer sets output Q to ON after a preset time delay. Elapsed time is accumulated over
multiple timing periods until the R input is used to
reset the elapsed time.

PRESET_TIMER(
PT:=_time_in_,

The PT (Preset timer) coil loads a new PRESET
time value in the specified IEC_Timer.

TIMER:=_iec_timer_in_);
FBD only:

RESET_TIMER(
_iec_timer_in_);

The RT (Reset timer) coil resets the specified
IEC_Timer.

STEP 7 automatically creates the DB when you insert the instruction.

In the SCL examples, "IEC_Timer_0_DB" is the name of the instance DB.

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Table 8- 19

Data types for the parameters

Parameter

Data type

Description

Box: IN
Coil: Power flow

Bool

TP, TON, and TONR:
Box: 0=Disable timer, 1=Enable timer
Coil: No power flow=Disable timer, Power flow=Enable timer
TOF:
Box: 0=Enable timer, 1=Disable timer
Coil: No power flow=Enable timer, Power flow=Disable timer

Bool

TONR box only:
0=No reset
1= Reset elapsed time and Q bit to 0

Box: PT
Coil: "PRESET_Tag"

Time

Timer box or coil: Preset time input

Box: Q
Coil: DBdata.Q

Bool

Timer box: Q box output or Q bit in the timer DB data
Timer coil: you can only address the Q bit in the timer DB data

Box: ET
Coil: DBdata.ET

Time

Timer box: ET (elapsed time) box output or ET time value in the timer DB
data
Timer coil: you can only address the ET time value in the timer DB data.

Table 8- 20

Effect of value changes in the PT and IN parameters

Timer

Changes in the PT and IN box parameters and the corresponding coil parameters

•

Changing PT has no effect while the timer runs.

•

Changing IN has no effect while the timer runs.

•

Changing PT has no effect while the timer runs.

•

Changing IN to FALSE, while the timer runs, resets and stops the timer.

•

Changing PT has no effect while the timer runs.

•

Changing IN to TRUE, while the timer runs, resets and stops the timer.

•

Changing PT has no effect while the timer runs, but has an effect when the timer resumes.

•

Changing IN to FALSE, while the timer runs, stops the timer but does not reset the timer. Changing
IN back to TRUE will cause the timer to start timing from the accumulated time value.

TON
TOF
TONR

PT (preset time) and ET (elapsed time) values are stored in the specified IEC_TIMER DB
data as signed double integers that represent milliseconds of time. TIME data uses the T#
identifier and can be entered as a simple time unit (T#200ms or 200) and as compound time
units like T#2s_200ms.
Table 8- 21
Data type
TIME
1

Size and range of the TIME data type
Size
32 bits, stored
as DInt data

Valid number ranges1
T#-24d_20h_31m_23s_648ms to T#24d_20h_31m_23s_647ms
Stored as -2,147,483,648 ms to +2,147,483,647 ms

The negative range of the TIME data type shown above cannot be used with the timer instructions. Negative PT (preset
time) values are set to zero when the timer instruction is executed. ET (elapsed time) is always a positive value.

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8.2 Timer operations

Timer coil example
The -(TP)-, -(TON)-, -(TOF)-, and -(TONR)- timer coils must be the last instruction in a LAD
network. As shown in the timer example, a contact instruction in a subsequent network
evaluates the Q bit in a timer coil's IEC_Timer DB data. Likewise, you must address the
ELAPSED element in the IEC_timer DB data if you want to use the elapsed time value in
your program.

The pulse timer is started on a 0 to 1 transition of the Tag_Input bit value. The timer runs for
the time specified by Tag_Time time value.

As long as the timer runs, the state of DB1.MyIEC_Timer.Q=1 and the Tag_Output value=1.
When the Tag_Time value has elapsed, then DB1.MyIEC_Timer.Q=0 and the Tag_Output
value=0.

Reset timer -(RT)- and Preset timer -(PT)- coils
These coil instructions can be used with box or coil timers and can be placed in a mid-line
position. The coil output power flow status is always the same as the coil input status. When
the -(RT)- coil is activated, the ELAPSED time element of the specified IEC_Timer DB data
is reset to 0. When the -(PT)- coil is activated, the PRESET time element of the specified
IEC_Timer DB data is loaded with the assigned time-duration value..
Note
When you place timer instructions in an FB, you can select the "Multi-instance data block"
option. The timer structure names can be different with separate data structures, but the
timer data is contained in a single data block and does not require a separate data block for
each timer. This reduces the processing time and data storage necessary for handling the
timers. There is no interaction between the timer data structures in the shared multi-instance
DB.

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Operation of the timers
Table 8- 22

Types of IEC timers

Timer

Timing diagram

TP: Generate pulse
The TP timer generates a pulse with a preset width
time.

TON: Generate ON-delay
The TON timer sets output Q to ON after a preset time
delay.

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Timer

Timing diagram

TOF: Generate OFF-delay
The TOF timer resets output Q to OFF after a preset
time delay.

TONR: Time accumulator
The TONR timer sets output Q to ON after a preset time
delay. Elapsed time is accumulated over multiple timing
periods until the R input is used to reset the elapsed
time.

Note
In the CPU, no dedicated resource is allocated to any specific timer instruction. Instead,
each timer utilizes its own timer structure in DB memory and a continuously-running internal
CPU timer to perform timing.
When a timer is started due to an edge change on the input of a TP, TON, TOF, or TONR
instruction, the value of the continuously-running internal CPU timer is copied into the
START member of the DB structure allocated for this timer instruction. This start value
remains unchanged while the timer continues to run, and is used later each time the timer is
updated. Each time the timer is started, a new start value is loaded into the timer structure
from the internal CPU timer.
When a timer is updated, the start value described above is subtracted from the current
value of the internal CPU timer to determine the elapsed time. The elapsed time is then
compared with the preset to determine the state of the timer Q bit. The ELAPSED and Q
members are then updated in the DB structure allocated for this timer. Note that the elapsed
time is clamped at the preset value (the timer does not continue to accumulate elapsed time
after the preset is reached).

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8.2 Timer operations
A timer update is performed when and only when:
● A timer instruction (TP, TON, TOF, or TONR) is executed
● The "ELAPSED" member of the timer structure in DB is referenced directly by an
instruction
● The "Q" member of the timer structure in DB is referenced directly by an instruction

Timer programming
The following consequences of timer operation should be considered when planning and
creating your user program:
● You can have multiple updates of a timer in the same scan. The timer is updated each
time the timer instruction (TP, TON, TOF, TONR) is executed and each time the
ELAPSED or Q member of the timer structure is used as a parameter of another
executed instruction. This is an advantage if you want the latest time data (essentially an
immediate read of the timer). However, if you desire to have consistent values throughout
a program scan, then place your timer instruction prior to all other instructions that need
these values, and use tags from the Q and ET outputs of the timer instruction instead of
the ELAPSED and Q members of the timer DB structure.
● You can have scans during which no update of a timer occurs. It is possible to start your
timer in a function, and then cease to call that function again for one or more scans. If no
other instructions are executed which reference the ELAPSED or Q members of the timer
structure, then the timer will not be updated. A new update will not occur until either the
timer instruction is executed again or some other instruction is executed using ELAPSED
or Q from the timer structure as a parameter.
● Although not typical, you can assign the same DB timer structure to multiple timer
instructions. In general, to avoid unexpected interaction, you should only use one timer
instruction (TP, TON, TOF, TONR) per DB timer structure.
● Self-resetting timers are useful to trigger actions that need to occur periodically. Typically,
self-resetting timers are created by placing a normally-closed contact which references
the timer bit in front of the timer instruction. This timer network is typically located above
one or more dependent networks that use the timer bit to trigger actions. When the timer
expires (elapsed time reaches preset value), the timer bit is ON for one scan, allowing the
dependent network logic controlled by the timer bit to execute. Upon the next execution of
the timer network, the normally closed contact is OFF, thus resetting the timer and
clearing the timer bit. The next scan, the normally closed contact is ON, thus restarting
the timer. When creating self-resetting timers such as this, do not use the "Q" member of
the timer DB structure as the parameter for the normally-closed contact in front of the
timer instruction. Instead, use the tag connected to the "Q" output of the timer instruction
for this purpose. The reason to avoid accessing the Q member of the timer DB structure
is because this causes an update to the timer and if the timer is updated due to the
normally closed contact, then the contact will reset the timer instruction immediately. The
Q output of the timer instruction will not be ON for the one scan and the dependent
networks will not execute.

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Time data retention after a RUN-STOP-RUN transition or a CPU power cycle
If a run mode session is ended with stop mode or a CPU power cycle and a new run mode
session is started, then the timer data stored in the previous run mode session is lost, unless
the timer data structure is specified as retentive (TP, TON, TOF, and TONR timers).
When you accept the defaults in the call options dialog after you place a timer instruction in
the program editor, you are automatically assigned an instance DB which cannot be made
retentive. To make your timer data retentive, you must either use a global DB or a Multiinstance DB.

Assign a global DB to store timer data as retentive data
This option works regardless of where the timer is placed (OB, FC, or FB).
1. Create a global DB:
– Double-click "Add new block" from the Project tree
– Click the data block (DB) icon
– For the Type, choose global DB
– If you want to be able to select individual data elements in this DB as retentive, be
sure the DB type "Optimized" box is checked. The other DB type option "Standard compatible with S7-300/400" only allows setting all DB data elements retentive or
none retentive.
– Click OK
2. Add timer structure(s) to the DB:
– In the new global DB, add a new static tag using data type IEC_Timer.
– In the "Retain" column, check the box so that this structure will be retentive.
– Repeat this process to create structures for all the timers that you want to store in this
DB. You can either place each timer structure in a unique global DB, or you can place
multiple timer structures into the same global DB. You can also place other static tags
besides timers in this global DB. Placing multiple timer structures into the same global
DB allows you to reduce your overall number of blocks.
– Rename the timer structures if desired.
3. Open the program block for editing where you want to place a retentive timer (OB, FC, or
FB).
4. Place the timer instruction at the desired location.
5. When the call options dialog appears, click the cancel button.
6. On the top of the new timer instruction, type the name (do not use the helper to browse)
of the global DB and timer structure that you created above (example:
"Data_block_3.Static_1").

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Assign a multi-instance DB to store timer data as retentive data
This option only works if you place the timer in an FB.
This option depends upon whether the FB properties specify "Optimized block access"
(allows symbolic access only). To verify how the access attribute is configured for an existing
FB, right-click on the FB in the Project tree, choose properties, and then choose Attributes.
If the FB specifies "Optimized block access" (allows symbolic access only):
1. Open the FB for edit.
2. Place the timer instruction at the desired location in the FB.
3. When the Call options dialog appears, click the Multi instance icon. The Multi Instance
option is only available if the instruction is being placed into an FB.
4. In the Call options dialog, rename the timer if desired.
5. Click OK. The timer instruction appears in the editor, and the IEC_TIMER structure
appears in the FB Interface under Static.
6. If necessary, open the FB interface editor (may have to click on the small arrow to expand
the view).
7. Under Static, locate the timer structure that was just created for you.
8. In the Retain column for this timer structure, change the selection to "Retain". Whenever
this FB is called later from another program block, an instance DB will be created with this
interface definition which contains the timer structure marked as retentive.
If the FB does not specify "Optimized block access", then the block access type is standard,
which is compatible with S7-300/400 classic configurations and allows symbolic and direct
access. To assign a multi-instance to a standard block access FB, follow these steps:
1. Open the FB for edit.
2. Place the timer instruction at the desired location in the FB.
3. When the Call options dialog appears, click on the multi instance icon. The multi instance
option is only available if the instruction is being placed into an FB.
4. In the Call options dialog, rename the timer if desired.
5. Click OK. The timer instruction appears in the editor, and the IEC_TIMER structure
appears in the FB Interface under Static.
6. Open the block that will use this FB.
7. Place this FB at the desired location. Doing so results in the creation of an instance data
block for this FB.
8. Open the instance data block created when you placed the FB in the editor.
9. Under Static, locate the timer structure of interest. In the Retain column for this timer
structure, check the box to make this structure retentive.

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8.3 Counter operations

8.3
Table 8- 23

Counter operations
Counter instructions

LAD / FBD

SCL
"IEC_Counter_0_DB".CTU
(
CU:=_bool_in,
R:=_bool_in,
PV:=_in,
Q=>_bool_out,
CV=>_out);
"IEC_Counter_0_DB".CTD
(
CD:=_bool_in,
LD:=_bool_in,
PV:=_in,
Q=>_bool_out,
CV=>_out);
"IEC_Counter_0_DB".CTU
D(
CU:=_bool_in,
CD:=_bool_in,
R:=_bool_in,
LD:=_bool_in,
PV:=_in_,
QU=>_bool_out,
QD=>_bool_out,
CV=>_out_);

Description
Use the counter instructions to count internal program events and
external process events. Each counter uses a structure stored in a
data block to maintain counter data. You assign the data block when
the counter instruction is placed in the editor.
•

CTU is a count-up counter

•

CTD is a count-down counter

•

CTUD is a count-up-and-down counter

For LAD and FBD: Select the count value data type from the drop-down list below the instruction name.

STEP 7 automatically creates the DB when you insert the instruction.

In the SCL examples, "IEC_Counter_0_DB" is the name of the instance DB.

Table 8- 24

Data types for the parameters

Parameter

Data type1

Description

CU, CD

Bool

Count up or count down, by one count

R (CTU, CTUD)

Bool

Reset count value to zero

LD (CTD, CTUD)

Bool

Load control for preset value

SInt, Int, DInt, USInt, UInt, UDInt

Preset count value

Q, QU

Bool

True if CV >= PV

Bool

True if CV <= 0

SInt, Int, DInt, USInt, UInt, UDInt

Current count value

The numerical range of count values depends on the data type you select. If the count value is an unsigned integer
type, you can count down to zero or count up to the range limit. If the count value is a signed integer, you can count
down to the negative integer limit and count up to the positive integer limit.

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8.3 Counter operations
The number of counters that you can use in your user program is limited only by the amount
of memory in the CPU. Counters use the following amount of memory:
● For SInt or USInt data types, the counter instruction uses 3 bytes.
● For Int or UInt data types, the counter instruction uses 6 bytes.
● For DInt or UDInt data types, the counter instruction uses 12 bytes.
These instructions use software counters whose maximum counting rate is limited by the
execution rate of the OB in which they are placed. The OB that the instructions are placed in
must be executed often enough to detect all transitions of the CU or CD inputs. For faster
counting operations, see the CTRL_HSC instruction (Page 555).
Note
When you place counter instructions in an FB, you can select the multi-instance DB option,
the counter structure names can be different with separate data structures, but the counter
data is contained in a single DB and does not require a separate DB for each counter. This
reduces the processing time and data storage necessary for the counters. There is no
interaction between the counter data structures in the shared multi-instance DB.

Operation of the counters
Table 8- 25

Operation of CTU (count up)

Counter

Operation

The CTU counter counts up by 1 when the value of parameter CU
changes from 0 to 1. The CTU timing diagram shows the operation for
an unsigned integer count value (where PV = 3).
•

If the value of parameter CV (current count value) is greater than or
equal to the value of parameter PV (preset count value), then the
counter output parameter Q = 1.

•

If the value of the reset parameter R changes from 0 to 1, then the
current count value is reset to 0.

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8.3 Counter operations
Table 8- 26

Operation of CTD (count down)

Counter

Operation

The CTD counter counts down by 1 when the value of parameter CD changes from 0 to 1. The CTD timing diagram shows
the operation for an unsigned integer count value (where PV =
3).
•

If the value of parameter CV (current count value) is equal
to or less than 0, the counter output parameter Q = 1.

•

If the value of parameter LOAD changes from 0 to 1, the
value at parameter PV (preset value) is loaded to the counter as the new CV (current count value).

Table 8- 27

Operation of CTUD (count up and down)

Counter

Operation

The CTUD counter counts up or
down by 1 on the 0 to 1 transition of the count up (CU) or
count down (CD) inputs. The
CTUD timing diagram shows the
operation for an unsigned integer count value (where PV = 4).
•

If the value of parameter CV
is equal to or greater than the
value of parameter PV, then
the counter output parameter
QU = 1.

•

If the value of parameter CV
is less than or equal to zero,
then the counter output parameter QD = 1.

•

If the value of parameter
LOAD changes from 0 to 1,
then the value at parameter
PV is loaded to the counter
as the new CV.

•

If the value of the reset parameter R is changes from 0
to 1, the current count value
is reset to 0.

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Counter data retention after a RUN-STOP-RUN transition or a CPU power cycle
If a run mode session is ended with stop mode or a CPU power cycle and a new run mode
session is started, then the counter data stored in the previous run mode session is lost,
unless the counter data structure is specified as retentive (CTU, CTD, and CTUD counters).
When you accept the defaults in the call options dialog after you place a counter instruction
in the program editor, you are automatically assigned an instance DB which cannot be made
retentive. To make your counter data retentive, you must either use a global DB or a Multiinstance DB.

Assign a global DB to store counter data as retentive data
This option works regardless of where the counter is placed (OB, FC, or FB).
1. Create a global DB:
– Double-click "Add new block" from the Project tree
– Click the data block (DB) icon
– For the Type, choose global DB
– If you want to be able to select individual items in this DB as retentive, be sure the
symbolic-access-only box is checked.
– Click OK
2. Add counter structure(s) to the DB:
– In the new global DB, add a new static tag using one of the counter data types. Be
sure to consider the Type you want to use for your Preset and Count values.
– In the "Retain" column, check the box so that this structure will be retentive.
– Repeat this process to create structures for all the counters that you want to store in
this DB. You can either place each counter structure in a unique global DB, or you can
place multiple counter structures into the same global DB. You can also place other
static tags besides counters in this global DB. Placing multiple counter structures into
the same global DB allows you to reduce your overall number of blocks.
– Rename the counter structures if desired.
3. Open the program block for editing where you want to place a retentive counter (OB, FC,
or FB).
4. Place the counter instruction at the desired location.

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5. When the call options dialog appears, click the cancel button. You should now see a new
counter instruction which has "???" both just above and just below the instruction name.
6. On the top of the new counter instruction, type the name (do not use the helper to
browse) of the global DB and counter structure that you created above (example:
"Data_block_3.Static_1"). This causes the corresponding preset and count value type to
be filled in (example: UInt for an IEC_UCounter structure).
Counter Data Type

Corresponding Type for the Preset and Count Values

IEC_Counter

INT

IEC_SCounter

SINT

IEC_DCounter

DINT

IEC_UCounter

UINT

IEC_USCounter

USINT

IEC_UDCounter

UDINT

Assign a multi-instance DB to store counter data as retentive data
This option only works if you place the counter in an FB.
This option depends upon whether the FB properties specify "Optimized block access"
(allows symbolic access only). To verify how the access attribute is configured for an existing
FB, right-click on the FB in the Project tree, choose properties, and then choose Attributes.
If the FB specifies "Optimized block access" (allows symbolic access only):
1. Open the FB for edit.
2. Place the counter instruction at the desired location in the FB.
3. When the Call options dialog appears, click on the Multi instance icon. The Multi Instance
option is only available if the instruction is being placed into an FB.
4. In the Call options dialog, rename the counter if desired.
5. Click OK. The counter instruction appears in the editor with type INT for the preset and
count values, and the IEC_COUNTER structure appears in the FB Interface under Static.
6. If desired, change the type in the counter instruction from INT to one of the other types.
The counter structure will change correspondingly.
7. If necessary, open the FB interface editor (may have to click on the small arrow to expand
the view).
8. Under Static, locate the counter structure that was just created for you.
9. In the Retain column for this counter structure, change the selection to "Retain".
Whenever this FB is called later from another program block, an instance DB will be
created with this interface definition which contains the counter structure marked as
retentive.

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8.3 Counter operations
If the FB does not specify "Optimized block access", then the block access type is standard,
which is compatible with S7-300/400 classic configurations and allows symbolic and direct
access. To assign a multi-instance to a standard block access FB, follow these steps:
1. Open the FB for edit.
2. Place the counter instruction at the desired location in the FB.
3. When the Call options dialog appears, click on the multi instance icon. The multi instance
option is only available if the instruction is being placed into an FB.
4. In the Call options dialog, rename the counter if desired.
5. Click OK. The counter instruction appears in the editor with type INT for the preset and
count value, and the IEC_COUNTER structure appears in the FB Interface under Static.
6. If desired, change the type in the counter instruction from INT to one of the other types.
The counter structure will change correspondingly.
7. Open the block that will use this FB.
8. Place this FB at the desired location. Doing so results in the creation of an instance data
block for this FB.
9. Open the instance data block created when you placed the FB in the editor.
10.Under Static, locate the counter structure of interest. In the Retain column for this counter
structure, check the box to make this structure retentive.
Type shown in counter instruction (for preset Corresponding structure Type shown in FB
and count values)
interface
INT

IEC_Counter

SINT

IEC_SCounter

DINT

IEC_DCounter

UINT

IEC_UCounter

USINT

IEC_USCounter

UDINT

IEC_UDCounter

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8.4 Comparator operations

8.4

Comparator operations

8.4.1

Compare values instructions

Table 8- 28

Compare instructions

LAD

FBD

SCL
out := in1 = in2;
or
IF in1 = in2
THEN out := 1;
ELSE out := 0;
END_IF;

Description
Compares two values of the same data type. When the
LAD contact comparison is TRUE, then the contact is
activated. When the FBD box comparison is TRUE,
then the box output is TRUE.

For LAD and FBD: Click the instruction name (such as "==") to change the comparison type from the drop-down list.
Click the "???" and select data type from the drop-down list.

Table 8- 29

Data types for the parameters

Parameter

Data type

Description

IN1, IN2

Byte, Word, DWord, SInt, Int, DInt, USInt, UInt, UDInt, Real,
LReal, String, WString, Char, Char, Time, Date, TOD, DTL,
Constant

Values to compare

Table 8- 30

Comparison descriptions

Relation type

The comparison is true if ...
=

IN1 is equal to IN2

IN1 is not equal to IN2

IN1 is greater than or equal to IN2

IN1 is less than or equal to IN2

IN1 is greater than IN2

IN1 is less than IN2

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8.4 Comparator operations

8.4.2
Table 8- 31

IN_Range (Value within range) and OUT_Range (Value outside range)
Value within Range and value outside range instructions

LAD / FBD

SCL
out := IN_RANGE(min,
val, max);

Description
Tests whether an input value is in or out of a specified value range.
If the comparison is TRUE, then the box output is TRUE.

out := OUT_RANGE(min,
val, max);

For LAD and FBD: Click the "???" and select the data type from the drop-down list.

Table 8- 32

Data types for the parameters

Parameter

Data type1

Description

MIN, VAL, MAX

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal,
Constant

Comparator inputs

The input parameters MIN, VAL, and MAX must be the same data type.

● The IN_RANGE comparison is true if: MIN <= VAL <= MAX
● The OUT_RANGE comparison is true if: VAL < MIN or VAL > MAX

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8.4.3
Table 8- 33
LAD

OK (Check validity) and NOT_OK (Check invalidity)
OK (check validity) and Not OK (check invalidity) instructions
FBD

SCL

Description

Not available

Tests whether an input data reference is a valid real number according to IEEE specification 754.

Not available

For LAD and FBD: When the LAD contact is TRUE, the contact is activated and passes power flow. When the FBD box
is TRUE, then the box output is TRUE.

Table 8- 34
Parameter

Data type

Description

Real, LReal

Input data

Table 8- 35

Data types for the parameter

Operation

Instruction

The Real number test is TRUE if:

The input value is a valid real number 1

NOT_OK

The input value is not a valid real number 1

A Real or LReal value is invalid if it is +/- INF (infinity), NaN (Not a Number), or if it is a denormalized value. A denormalized value is a number very close to zero. The CPU substitutes a zero for a denormalized value in calculations.

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Basic instructions
8.4 Comparator operations

8.4.4

Variant and array comparison instructions

8.4.4.1

Equality and non-equality comparison instructions
The S7-1200 CPU provides instructions for querying the data type of a tag to which a Variant
operand points for either equality or non-equality to the data type of the other operand.
In addition, the S7-1200 CPU provides instructions for querying the data type of an array
element for either equality or non-equality to the data type of the other operand.
In these instructions, you are comparing to . must
have the Variant data type. can be an elementary data type of a PLC data type.
In LAD and FBD, is the operand above the instruction. In LAD, is
the operand below the instruction.
For all instructions, the result of logic operation (RLO) is 1 (true) if the equality or nonequality test passes, and is 0 (false) if not.
The equality and non-equality type comparison instructions are as follows:
● EQ_Type (Compare data type for EQUAL with the data type of a tag)
● NE_Type (Compare data type for UNEQUAL with the data type of a tag)
● EQ_ElemType (Compare data type of an ARRAY element for EQUAL with the data type
of a tag)
● NE_ElemType (Compare data type of an ARRAY element for UNEQUAL with the data
type of a tag)

Table 8- 36
LAD

EQ and NE instructions
FBD

SCL

Description

Not available

Tests whether the tag pointed to by the Variant
at Operand1 is of the same data type as the
tag at Operand2.

Not available

Tests whether the tag pointed to by the Variant
at Operand1 is of a different data type as the
tag at Operand2.

Not available

Tests whether the array element pointed to by
the Variant at Operand1 is of the same data
type as the tag at Operand2.

Not available

Tests whether the array element pointed to by
the Variant at Operand1 is of a different data
type as the tag at Operand2.

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8.4 Comparator operations
Table 8- 37

Data types for the parameters

Parameter

Data type

Description

Operand1

Variant

First operand

Operand2

Bit strings, integers, floating-point numbers,
timers, date and time, character strings,
ARRAY, PLC data types

Second operand

8.4.4.2

Null comparsion instructions
You can use the instructions IS_NULL and NOT_NULL to determine whether or not the input
actually points to an object or not.
For both instructions, must have the Variant data type.

Table 8- 38
LAD

Table 8- 39

IS_NULL (Query for EQUALS ZERO pointer) and NOT_NULL (Query for EQUALS ZERO pointer) instructions
FBD

SCL

Description

Not available

Tests whether the tag pointed to by the Variant
at Operand is null and therefore not an object.

Not available

Tests whether the tag pointed to by the Variant
at Operand is not null and therefore does point
to an object.

Data types for the parameters

Parameter

Data type

Description

Operand

Variant

Operand to evaluate for null or not null.

8.4.4.3

IS_ARRAY (Check for ARRAY)
You can use the "Check for ARRAY" instruction to query whether the Variant points to a tag
of the Array data type.
The must have the Variant data type.
The instructions returns 1 (true) if the operand is an array.

Table 8- 40
LAD

IS_ARRAY (Check for ARRAY)
FBD

SCL

Description

IS_ARRAY(_variant_in_)

Tests whether the tag pointed to by the Variant
at Operand is an array.

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Basic instructions
8.5 Math functions
Table 8- 41

Data types for the parameters

Parameter

Data type

Description

Operand

Variant

Operand to evaluate for whether it is an array.

8.5

Math functions

8.5.1

CALCULATE (Calculate)

Table 8- 42

CALCULATE instruction

LAD / FBD

SCL

Description

Use the standard SCL math
expressions to
create the equation.

The CALCULATE instruction lets you create a math function that operates on inputs (IN1, IN2, .. INn) and produces the result at OUT, according to the equation that you define.

Table 8- 43

•

Select a data type first. All inputs and the output must be the same
data type.

•

To add another input, click the icon at the last input.

Data types for the parameters

Parameter

Data type1

IN1, IN2, ..INn

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word, DWord

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word, DWord

The IN and OUT parameters must be the same data type (with implicit conversions of the input parameters). For example: A SINT value for an input would be converted to an INT or a REAL value if OUT is an INT or REAL

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Basic instructions
8.5 Math functions
Click the calculator icon to open the dialog and define your math function. You enter your
equation as inputs (such as IN1 and IN2) and operations. When you click "OK" to save the
function, the dialog automatically creates the inputs for the CALCULATE instruction.
The dialog shows an example and a list of possible instructions that you can include based
on the data type of the OUT parameter:

Note
You also must create an input for any constants in your function. The constant value would
then be entered in the associated input for the CALCULATE instruction.
By entering constants as inputs, you can copy the CALCULATE instruction to other locations
in your user program without having to change the function. You then can change the values
or tags of the inputs for the instruction without modifying the function.
When CALCULATE is executed and all the individual operations in the calculation complete
successfully, then the ENO = 1. Otherwise, ENO = 0.
For an example of the CALCULATE instruction, see "Creating a complex equation with a
simple instruction (Page 42)".

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Basic instructions
8.5 Math functions

8.5.2
Table 8- 44
LAD / FBD

Add, subtract, multiply and divide instructions
SCL
out
out
out
out

:=
:=
:=
:=

in1
in1
in1
in1

+
*
/

in2;
in2;
in2;
in2;

Description
•

ADD: Addition (IN1 + IN2 = OUT)

•

SUB: Subtraction (IN1 - IN2 = OUT)

•

MUL: Multiplication (IN1 * IN2 = OUT)

• DIV: Division (IN1 / IN2 = OUT)
An Integer division operation truncates the fractional part of the quotient
to produce an integer output.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 45

Add, subtract, multiply and divide instructions

Data types for the parameters (LAD and FBD)

Parameter

Data type1

Description

IN1, IN2

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Constant

Math operation inputs

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal

Math operation output

Parameters IN1, IN2, and OUT must be the same data type.

To add an ADD or MUL input, click the "Create" icon or right-click on an input
stub for one of the existing IN parameters and select the "Insert input" command.
To remove an input, right-click on an input stub for one of the existing IN parameters (when
there are more than the original two inputs) and select the "Delete" command.
When enabled (EN = 1), the math instruction performs the specified operation on the input
values (IN1 and IN2) and stores the result in the memory address specified by the output
parameter (OUT). After the successful completion of the operation, the instruction sets ENO
= 1.

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8.5 Math functions
Table 8- 46
ENO

Description

No error

The Math operation result value would be outside the valid number range of the data type selected. The
least significant part of the result that fits in the destination size is returned.

Division by 0 (IN2 = 0): The result is undefined and zero is returned.

Real/LReal: If one of the input values is NaN (not a number) then NaN is returned.

ADD Real/LReal: If both IN values are INF with different signs, this is an illegal operation and NaN is returned.

SUB Real/LReal: If both IN values are INF with the same sign, this is an illegal operation and NaN is returned.

MUL Real/LReal: If one IN value is zero and the other is INF, this is an illegal operation and NaN is returned.

DIV Real/LReal: If both IN values are zero or INF, this is an illegal operation and NaN is returned.

8.5.3

MOD (return remainder of division)

Table 8- 47
LAD / FBD

Modulo (return remainder of division) instruction
SCL
out := in1 MOD in2;

Description
You can use the MOD instruction to return the remainder of an integer
division operation. The value at the IN1 input is divided by the value at
the IN2 input and the remainder is returned at the OUT output.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 48

ENO status

Data types for parameters

Parameter

Data type1

Description

IN1 and IN2

SInt, Int, DInt, USInt, UInt, UDInt, Constant

Modulo inputs

OUT

SInt, Int, DInt, USInt, UInt, UDInt

Modulo output

The IN1, IN2, and OUT parameters must be the same data type.

Table 8- 49
ENO

ENO values
Description

No error

Value IN2 = 0, OUT is assigned the value zero

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Basic instructions
8.5 Math functions

8.5.4
Table 8- 50
LAD / FBD

NEG (Create twos complement)
NEG (create twos complement) instruction
SCL
-(in);

Description
The NEG instruction inverts the arithmetic sign of the value at parameter IN and stores
the result in parameter OUT.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 51

Data types for parameters

Parameter

Data type1

Description

SInt, Int, DInt, Real, LReal, Constant

Math operation input

OUT

SInt, Int, DInt, Real, LReal

Math operation output

The IN and OUT parameters must be the same data type.

Table 8- 52

ENO status

ENO

Description

No error

The resulting value is outside the valid number range of the selected data type.
Example for SInt: NEG (-128) results in +128 which exceeds the data type maximum.

8.5.5
Table 8- 53
LAD / FBD

INC (Increment) and DEC (Decrement)
INC and DEC instructions
SCL
in_out := in_out + 1;

Description

in_out := in_out - 1;

Decrements a signed or unsigned integer number value:

Increments a signed or unsigned integer number value:
IN_OUT value +1 = IN_OUT value

IN_OUT value - 1 = IN_OUT value

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

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8.5 Math functions
Table 8- 54

Data types for parameters

Parameter

Data type

Description

IN/OUT

SInt, Int, DInt, USInt, UInt, UDInt

Math operation input and output

Table 8- 55

ENO status

ENO

Description

No error

The resulting value is outside the valid number range of the selected data type.
Example for SInt: INC (+127) results in +128, which exceeds the data type maximum.

8.5.6
Table 8- 56
LAD / FBD

ABS (Form absolute value)
ABS (absolute value) instruction
SCL
out := ABS(in);

Description
Calculates the absolute value of a signed integer or real number at parameter
IN and stores the result in parameter OUT.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 57

Data types for parameters

Parameter

Data type1

Description

SInt, Int, DInt, Real, LReal

Math operation input

OUT

SInt, Int, DInt, Real, LReal

Math operation output

The IN and OUT parameters must be the same data type.

Table 8- 58

ENO status

ENO

Description

No error

The math operation result value is outside the valid number range of the selected data type.
Example for SInt: ABS (-128) results in +128 which exceeds the data type maximum.

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Basic instructions
8.5 Math functions

8.5.7
Table 8- 59

MIN (Get minimum) and MAX (Get maximum)
MIN (get minimum) and MAX (get maximum) instructions

LAD / FBD

SCL
out:= MIN(
in1:=_variant_in_,
in2:=_variant_in_
[,...in32]);

out:= MAX(
in1:=_variant_in_,
in2:=_variant_in_
[,...in32]);

Description
The MIN instruction compares the value of two parameters IN1
and IN2 and assigns the minimum (lesser) value to parameter
OUT.

The MAX instruction compares the value of two parameters IN1
and IN2 and assigns the maximum (greater) value to parameter
OUT.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 60

Data types for the parameters

Parameter

Data type1

Description

IN1, IN2
[...IN32]

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Time,
Date, TOD, Constant

Math operation inputs (up to 32 inputs)

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Time,
Date, TOD

Math operation output

The IN1, IN2, and OUT parameters must be the same data type.

To add an input, click the "Create" icon or right-click on an input stub for one of
the existing IN parameters and select the "Insert input" command.
To remove an input, right-click on an input stub for one of the existing IN parameters (when
there are more than the original two inputs) and select the "Delete" command.
Table 8- 61

ENO status

ENO

Description

No error

For Real data type only:
•

At least one input is not a real number (NaN).

•

The resulting OUT is +/- INF (infinity).

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8.5 Math functions

8.5.8
Table 8- 62

LIMIT (Set limit value)
LIMIT (set limit value) instruction

LAD / FBD

SCL
LIMIT(MN:=_variant_in_,
IN:=_variant_in_,
MX:=_variant_in_,
OUT:=_variant_out_);

Description
The Limit instruction tests if the value of parameter IN is inside the
value range specified by parameters MIN and MAX and if not,
clamps the value at MIN or MAX.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 63

Data types for the parameters

Parameter

Data type1

Description

MN, IN, and MX

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Time, Date,
TOD·Constant

Math operation inputs

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Time, Date,
TOD

Math operation output

The MN, IN, MX, and OUT parameters must be the same data type.

If the value of parameter IN is within the specified range, then the value of IN is stored in
parameter OUT. If the value of parameter IN is outside of the specified range, then the OUT
value is the value of parameter MIN (if the IN value is less than the MIN value) or the value
of parameter MAX (if the IN value is greater than the MAX value).
Table 8- 64

ENO status

ENO

Description

No error

Real: If one or more of the values for MIN, IN and MAX is NaN (Not a Number), then NaN is returned.

If MIN is greater than MAX, the value IN is assigned to OUT.

SCL examples:
● MyVal := LIMIT(MN:=10,IN:=53, MX:=40); //Result: MyVal = 40
● MyVal := LIMIT(MN:=10,IN:=37, MX:=40); //Result: MyVal = 37
● MyVal := LIMIT(MN:=10,IN:=8, MX:=40); //Result: MyVal = 10

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8.5 Math functions

8.5.9

Exponent, logarithm, and trigonometry instructions
You use the floating point instructions to program mathematical operations using a Real or
LReal data type:
● SQR: Form square (IN 2 = OUT)
● SQRT: Form square root (√IN = OUT)
● LN: Form natural logarithm (LN(IN) = OUT)
● EXP: Form exponential value (e IN =OUT), where base e = 2.71828182845904523536
● EXPT: exponentiate (IN1 IN2 = OUT)
EXPT parameters IN1 and OUT are always the same data type, for which you must
select Real or LReal. You can select the data type for the exponent parameter IN2 from
among many data types.
● FRAC: Return fraction (fractional part of floating point number IN = OUT)
● SIN: Form sine value (sin(IN radians) = OUT)
● ASIN: Form arcsine value (arcsine(IN) = OUT radians), where the sin(OUT radians) = IN
● COS: Form cosine (cos(IN radians) = OUT)
● ACOS: Form arccosine value (arccos(IN) = OUT radians), where the cos(OUT radians) =
IN
● TAN: Form tangent value (tan(IN radians) = OUT)
● ATAN: Form arctangent value (arctan(IN) = OUT radians), where the tan(OUT radians) =
IN

Table 8- 65
LAD / FBD

Examples of floating-point math instructions
SCL
out := SQR(in);
or
out := in * in;
out := in1 ** in2;

Description
Square: IN 2 = OUT
For example: If IN = 9, then OUT = 81.

General exponential: IN1 IN2 = OUT
For example: If IN1 = 3 and IN2 = 2, then OUT = 9.

For LAD and FBD: Click the "???" (by the instruction name) and select a data type from the drop-down menu.

For SCL: You can also use the basic SCL math operators to create the mathematical expressions.

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8.5 Math functions
Table 8- 66

Data types for parameters

Parameter

Data type

Description

IN, IN1

Real, LReal, Constant

Inputs

IN2

SInt, Int, DInt, USInt, UInt,UDInt, Real, LReal, Constant

EXPT exponent input

OUT

Real, LReal

Outputs

Table 8- 67

ENO status

ENO

Instruction

Condition

Result (OUT)

All

No error

Valid result

SQR

Result exceeds valid Real/LReal range

+INF

IN is +/- NaN (not a number)

+NaN

IN is negative

-NaN

IN is +/- INF (infinity) or +/- NaN

+/- INF or +/- NaN

IN is 0.0, negative, -INF, or -NaN

-NaN

IN is +INF or +NaN

+INF or +NaN

Result exceeds valid Real/LReal range

+INF

IN is +/- NaN

+/- NaN

SIN, COS, TAN

IN is +/- INF or +/- NaN

+/- INF or +/- NaN

ASIN, ACOS

IN is outside valid range of -1.0 to +1.0

+NaN

IN is +/- NaN

+/- NaN

ATAN

IN is +/- NaN

+/- NaN

FRAC

IN is +/- INF or +/- NaN

+NaN

EXPT

IN1 is +INF and IN2 is not -INF

+INF

IN1 is negative or -INF

+NaN if IN2 is Real/LReal,
-INF otherwise

IN1 or IN2 is +/- NaN

+NaN

IN1 is 0.0 and IN2 is Real/LReal (only)

+NaN

SQRT
LN
EXP

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Basic instructions
8.6 Move operations

8.6

Move operations

8.6.1

MOVE (Move value), MOVE_BLK (Move block), UMOVE_BLK (Move block
uninterruptible), and MOVE_BLK_VARIANT (Move block)
Use the Move instructions to copy data elements to a new memory address and convert
from one data type to another. The source data is not changed by the move process.
● The MOVE instruction copies a single data element from the source address specified by
the IN parameter to the destination addresses specified by the OUT parameter.
● The MOVE_BLK and UMOVE_BLK instructions have an additional COUNT parameter.
The COUNT specifies how many data elements are copied. The number of bytes per
element copied depends on the data type assigned to the IN and OUT parameter tag
names in the PLC tag table.

Table 8- 68

MOVE, MOVE_BLK, UMOVE_BLK, and MOVE_BLK_VARIANT instructions

LAD / FBD

SCL
out1 := in;

Description

MOVE_BLK(
in:=_variant_in,
count:=_uint_in,
out=>_variant_out);

Interruptible move that copies a block of data
elements to a new address.

UMOVE_BLK(
in:=_variant_in,
count:=_uint_in,
out=>_variant_out);

Uninterruptible move that copies a block of data
elements to a new address.

MOVE_BLK(
SRC:=_variant_in,
COUNT:=_udint_in,
SRC_INDEX:=_dint_in,

Moves the contents of a source memory area to
a destination memory area.

DEST_INDEX:=_dint_in,
DEST=>_variant_out);

Copies a data element stored at a specified
address to a new address or multiple addresses.1

You can copy a complete array or elements of
an array to another array of the same data type.
The size (number of elements) of source and
destination array may be different. You can
copy multiple or single elements within an array.
You use Variant data types to point to both the
source and destination arrays.

MOVE instruction: To add another output in LAD or FBD, click the "Create" icon by the output parameter. For SCL, use
multiple assignment statements. You might also use one of the loop constructions.

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Table 8- 69

Data types for the MOVE instruction

Parameter

Data type

Description

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word,
DWord, Char, WChar, Array, Struct, DTL, Time, Date, TOD,
IEC data types, PLC data types

Source address

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word,
DWord, Char, WChar, Array, Struct, DTL, Time, Date, TOD,
IEC data types, PLC data types

Destination address

To add MOVE outputs, click the "Create" icon or right-click on an output stub for
one of the existing OUT parameters and select the "Insert output" command.
To remove an output, right-click on an output stub for one of the existing OUT parameters
(when there are more than the original two outputs) and select the "Delete" command.
Table 8- 70

Data types for the MOVE_BLK and UMOVE_BLK instructions

Parameter

Data type

Description

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal Byte, Word,
DWord, Time, Date, TOD, WChar

Source start address

COUNT

UInt

Number of data elements to copy

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word,
DWord, Time, Date, TOD, WChar

Destination start address

Table 8- 71

Data types for the MOVE_BLK_VARIANT instruction

Parameter

Data type

Description

SRC

Variant (which points to an array or individual array element)

Source block from which to copy

COUNT

UDInt

Number of data elements to copy

SRC_INDEX

DInt

Zero-based index into the SRC array

DEST_INDEX

DInt

Zero-based index into the DEST
array

RET_VAL

Int

Error information

DEST

Variant (which points to an array or individualt array element)

Destination area into which to copy
the contents of the source block

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8.6 Move operations

Note
Rules for data copy operations
• To copy the Bool data type, use SET_BF, RESET_BF, R, S, or output coil (LAD)
(Page 230)
• To copy a single elementary data type, use MOVE
• To copy an array of an elementary data type, use MOVE_BLK or UMOVE_BLK
• To copy a structure, use MOVE
• To copy a string, use S_MOVE (Page 346)
• To copy a single character in a string, use MOVE
• The MOVE_BLK and UMOVE_BLK instructions cannot be used to copy arrays or
structures to the I, Q, or M memory areas.
MOVE_BLK and UMOVE_BLK instructions differ in how interrupts are handled:
● Interrupt events are queued and processed during MOVE_BLK execution. Use the
MOVE_BLK instruction when the data at the move destination address is not used within
an interrupt OB subprogram or, if used, the destination data does not have to be
consistent. If a MOVE_BLK operation is interrupted, then the last data element moved is
complete and consistent at the destination address. The MOVE_BLK operation is
resumed after the interrupt OB execution is complete.
● Interrupt events are queued but not processed until UMOVE_BLK execution is complete.
Use the UMOVE_BLK instruction when the move operation must be completed and the
destination data consistent, before the execution of an interrupt OB subprogram. For
more information, see the section on data consistency (Page 198).
ENO is always true following execution of the MOVE instruction.
Table 8- 72

ENO status

ENO

Condition

Result

No error

All COUNT elements were successfully copied.

Either the source (IN) range or the destination (OUT)
range exceeds the available memory area.

Elements that fit are copied. No partial elements are copied.

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8.6 Move operations
Table 8- 73
RET_VAL

Condition codes for the MOVE_BLK_VARIANT instruction
Description

(W#16#...)
0000

No error

80B4

Data types do not correspond.

8151

Access to the SRC parameter is not possible.

8152

The operand at the SRC parameter is an invalid type.

8153

Code generation error at the SRC parameter

8154

The operand at the SRC parameter has the data type Bool.

8281

The COUNT parameter has an invalid value.

8382

The value at the SRC_INDEX parameter is outside the limits of the
Variant.

8383

The value at parameter SRC_INDEX is outside the high limit of the
array.

8482

The value at the DEST_INDEX parameter is outside the limits of
the Variant.

8483

The value at parameter DEST_INDEX is outside the high limit of
the array.

8534

The DEST parameter is write-protected.

8551

Access to the DEST parameter is not possible.

8552

The operand at the DEST parameter is an invalid type.

8553

Code generation error at the DEST parameter

8554

The operand at the DEST parameter has the data type Bool.

*You can display error codes in the program editor as integer or hexadecimal values.

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8.6 Move operations

8.6.2

Deserialize
You can use the "Deserialize" instruction to convert the sequential representation of a PLC
data type (UDT) back to a PLC data type and to fill its entire contents. If the comparison is
TRUE, then the box output is TRUE.
The memory area which holds the sequential representation of a PLC data type must have
the Array of Byte data type and you must declare the data block to have standard (not
optimized) access. Make sure that there is enough memory space prior to the conversion.
The instruction enables you to convert multiple sequential representations of converted PLC
data types back to their original data types.
Note
If you only want to convert back a single sequential representation of a PLC data type (UDT),
you can also use the instruction "TRCV: Receive data via communication connection".

Table 8- 74

DESERIALIZE instruction

LAD / FBD

Table 8- 75

SCL
ret_val := Deserialize(
SRC_ARRAY:=_variant_in_,
DEST_VARIABLE=>_variant_out
_,
POS:=_dint_inout_);

Description
Converts the sequential representation of a PLC data type (UDT)
back to a PLC data type and fills
its entire contents

Parameters for the DESERIALIZE instruction

Parameter

Type

Data type

Description

SRC_ARRAY

Variant

Global data block that contains the data stream

DEST_VARIABLE

INOUT

Variant

Tag in which to store the
converted PLC data type
(UDT)

POS

INOUT

DInt

Number of bytes that the
converted PLC data type
uses

RET_VAL

OUT

Int

Error information

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Table 8- 76
RET_VAL*
(W#16#...)

RET_VAL parameter
Description

0000

No error

80B0

The memory areas for the SRC_ARRAY and DEST_VARIABLE parameters overlap.

8136

The data block at the DEST_VARIABLE parameter is not a block with standard access.

8150

The Variant data type at the SRC_ARRAY parameter contains no value.

8151

Code generation error at the SRC_ARRAY parameter.

8153

There is not enough free memory available at the SRC_ARRAY parameter.

8250

The Variant data type at the DEST_VARIABLE parameter contains no value.

8251

Code generation error at the DEST_VARIABLE parameter.

8254

Invalid data type at the DEST_VARIABLE parameter.

8382

The value at parameter POS is outside the limits of the array.

*You

can view the error codes as either integer or hexadecimal in the program editor.

Example: Deserialize instruction
The following example shows how the instruction works:
Network 1:

The "MOVE" instruction moves the value "0" to the "#BufferPos" data block tag. The
Deserialize instruction then deserializes the sequential representation of the customer data
from the "Buffer" data block and writes it to the "Target" data block. The Deserialize
instruction calculates the number of bytes that the converted data uses and stores it in the
"#BufferPos" data block tag.
Network 2:

The "Deserialize" instruction deserializes the sequential representation of the data stream
pointed to by "Buffer" and writes the characters to the "#Label" operand. The logic compares
the characters using the comparison instructions "arti" and "Bill". If the comparison for "arti" =
TRUE, the data is article data that is to be deserialized and written to the "Article" data
structure of the "Target" data block. If the comparison for "Bill" = TRUE, the data is billing
data that is to be deserialized and written to the "Bill" data structure of the "Target" data
block.
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Function block (or Function) interface:

Custom PLC data types:
The structure of the two PLC data types (UDTs) for this example are as follows:

Data blocks:
The two data blocks for this example are as follows:

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8.6.3

Serialize
You can use the "Serialize" instruction to convert several PLC data types (UDTs) to a
sequential representation without any loss of structure.
You can use the instruction to temporarily save multiple structured data items from your
program to a buffer, for example to a global data block, and send them to another CPU. The
memory area in which the converted PLC data types are stored must have the ARRAY of
BYTE data type and be declared with standard access. Make sure that there is enough
memory space prior to the conversion.
The POS parameter contains information about the number of bytes that the converted PLC
data types use.
Note
If you only want to send a single PLC data type (UDT), you can use the instruction "TSEND:
Send data via communication connection".

Table 8- 77

SERIALIZE instruction

LAD / FBD

Table 8- 78

SCL
ret_val := Serialize(
SRC_VARIABLE=>_variant_in_,
DEST_ARRAY:=_variant_out_,
POS:=_dint_inout_);

Description
Converts a PLC data type
(UDT) to a sequential representation.

Parameters for the SERIALIZE instruction

Parameter

Type

Data type

Description

SRC_VARIABLE

Variant

PLC data type (UDT) that is
to be converted to a serial
representation

DEST_ARRAY

INOUT

Variant

Data block in which the generated data stream is to be
stored

POS

INOUT

DInt

Number of bytes that the
converted PLC data types
use. The calculated POS
parameter is zero-based.

RET_VAL

OUT

Int

Error information

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Table 8- 79
RET_VAL*
(W#16#...)

RET_VAL parameter
Description

0000

No error

80B0

The memory areas for the SRC_VARIABLE and DEST_ARRAY parameters overlap.

8150

The Variant data type at the SRC_VARIABLE parameter contains no value.

8152

Code generation error at the SRC_VARIABLE parameter.

8236

The data block at the DEST_ARRAY parameter is not a block with standard access.

8250

The Variant data type at the DEST_ARRAY parameter contains no value.

8252

Code generation error at the DEST_ARRAY parameter.

8253

There is not enough free memory available at the DEST_ARRAY parameter.

8254

Invalid data type at the DEST_VARIABLE parameter.

8382

The value at parameter POS is outside the limits of the array.

*You

can view the error codes as either integer or hexadecimal in the program editor.

Example: Serialize instruction
The following example shows how the instruction works:
Network 1:

The "MOVE" instruction moves the value "0" to the "#BufferPos" parameter. The "Serialize"
instruction serializes the customer data from the "Source" data block and writes it in
sequential representation to the "Buffer" data block. The instruction stores the number of
bytes used by the sequential representation in the "#BufferPos" parameter.
Network 2:

The logic now inserts some separator text to make it easier to deserialize the sequential
representation later. The "S_MOVE" instruction moves the text string "arti" to the "#Label"
parameter. The "Serialize" instruction writes these characters after the source client data to
the "Buffer" data block. The instruction adds the number of bytes in the text string "arti" to the
number already stored in the "#BufferPos" parameter.
Network 3:

The "Serialize" instruction serializes the data of a specific article, which is calculated in
runtime, from the "Source" data block and writes it in sequential representation to the
"Buffer" data block after the "arti" characters
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Block Interface:

Custom PLC data types:
The structure of the two PLC data types (UDTs) for this example are as follows:

Data blocks:
The two data blocks for this example are as follows:

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8.6.4
Table 8- 80
LAD / FBD

FILL_BLK (Fill block) and UFILL_BLK (Fill block uninterruptible)
FILL_BLK and UFILL_BLK instructions
SCL
FILL_BLK(
in:=_variant_in,
count:=int,
out=>_variant_out);
UFILL_BLK(
in:=_variant_in,
count:=int,
out=>_variant_out);

Table 8- 81

Description
Interruptible fill instruction: Fills an address range with copies of a
specified data element

Uninterruptible fill instruction: Fills an address range with copies of
a specified data element

Data types for parameters

Parameter

Data type

Description

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word,
DWord, Time, Date, TOD, Char, WChar

Data source address

COUNT

UDint, USInt, UInt

Number of data elements to copy

OUT

SInt, Int, DInt, USInt, UInt, UDInt, Real, LReal, Byte, Word,
DWord, Time, Date, TOD, Char, WChar

Data destination address

Note
Rules for data fill operations
• To fill with the BOOL data type, use SET_BF, RESET_BF, R, S, or output coil (LAD)
• To fill with a single elementary data type, use MOVE
• To fill an array with an elementary data type, use FILL_BLK or UFILL_BLK
• To fill a single character in a string, use MOVE
• The FILL_BLK and UFILL_BLK instructions cannot be used to fill arrays in the I, Q, or M
memory areas.
The FILL_BLK and UFILL_BLK instructions copy the source data element IN to the
destination where the initial address is specified by the parameter OUT. The copy process
repeats and a block of adjacent addresses is filled until the number of copies is equal to the
COUNT parameter.
FILL_BLK and UFILL_BLK instructions differ in how interrupts are handled:
● Interrupt events are queued and processed during FILL_BLK execution. Use the
FILL_BLK instruction when the data at the move destination address is not used within an
interrupt OB subprogram or, if used, the destination data does not have to be consistent.
● Interrupt events are queued but not processed until UFILL_BLK execution is complete.
Use the UFILL_BLK instruction when the move operation must be completed and the
destination data consistent, before the execution of an interrupt OB subprogram.
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Table 8- 82

8.6.5
Table 8- 83
LAD / FBD

ENO status

ENO

Condition

Result

No error

The IN element was successfully copied to
all COUNT destinations.

The destination (OUT) range exceeds
the available memory area

Elements that fit are copied. No partial elements are copied.

SWAP (Swap bytes)
SWAP instruction
SCL
out := SWAP(in);

Description
Reverses the byte order for two-byte and four-byte data elements. No change
is made to the bit order within each byte. ENO is always TRUE following execution of the SWAP instruction.

For LAD and FBD: Click the "???" and select a data type from the drop-down menu.

Table 8- 84

Data types for the parameters

Parameter

Data type

Description

Word, DWord

Ordered data bytes IN

OUT

Word, DWord

Reverse ordered data bytes OUT

Example 1

Parameter IN = MB0
(before execution)

Parameter OUT = MB4,
(after execution)

Address

MW0

MB1

MW4

MB5

W#16#1234

WORD

MSB

LSB

MSB

LSB

Example 2

Parameter IN = MB0
(before execution)

Parameter OUT = MB4,
(after execution)

Address

MD0

MB1

MB2

MB3

MD4

MB5

MB6

MB7

DW#16#
12345678

DWORD

MSB

LSB

MSB

LSB

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8.6.6
Table 8- 85

LOWER_BOUND: (Read out ARRAY low limit)
LOWER_BOUND instruction

LAD / FBD

SCL
out := LOWER_BOUND(
ARR:=_variant_in_,
DIM:=_udint_in_);

Description
You can declare tags with ARRAY[*] in the block
interface. For these local tags, you can read out
the limits of the ARRAY. You will need to specify
the required dimension at the DIM parameter.
The LOWER_BOUND (Read out ARRAY low
limit). instruction lets you read out the variable
low limit of the ARRAY.

Parameters
The following table shows the parameters of the instruction "LOWER_BOUND: Read out
ARRAY low limit":
Parameters

Declaration

Data type

Memory area

Description

Input

BOOL

I, Q, M, D, L

Enable input

ENO

Output

BOOL

I, Q, M, D, L

Enable output ENO has the
signal state "0" if one of the
following conditions applies:
•

The EN enable input has
the signal state "0".

•

The dimension specified
at input DIM does not exist.

ARR

Input

ARRAY [*]

FB: Section InOut ARRAY of which the variable
FC: Sections Input low limit is to be read.
and InOut

DIM

Input

UDINT

I, Q, M, D, L or
constant

Dimension of the ARRAY of
which the variable low limit is
to be read.

OUT

Output

DINT

I, Q, M, D, L

Result

You can find additional information on valid data types under "Data types (Page 125)":

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Example
In the function (FC) block interface, the input parameter ARRAY_A is a one-dimensional
array with variable dimensions.

If the "Enable_Start" operand returns signal state "1", the CPU executes the
LOWER_BOUND instruction. It reads out the variable low limit of the ARRAY #ARRAY_A
from the one-dimensional array. If the instruction executes without errors, it sets operand
"Enable_Out" and sets the "Result" operand to the low limit of the array.

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8.6.7
Table 8- 86

UPPER_BOUND: (Read out ARRAY high limit)
LOWER_BOUND instruction

LAD / FBD

SCL
out := UPPER_BOUND(
ARR:=_variant_in_,
DIM:=_udint_in_);

Description
You can declare tags with ARRAY[*] in the block
interface. For these local tags, you can read out
the limits of the ARRAY. You will need to specify
the required dimension at the DIM parameter.
The UPPER_BOUND (Read out ARRAY high
limit) instruction lets you read out the variable
high limit of the ARRAY.

Parameters
The following table shows the parameters of the instruction "UPPER_BOUND: Read out
ARRAY high limit":
Parameters

Declaration

Data type

Memory area

Description

Input

BOOL

I, Q, M, D, L

Enable input

ENO

Output

BOOL

I, Q, M, D, L

Enable output

ARR

Input

ARRAY [*]

FB: Section InOut ARRAY of which the variable
FC: Sections Input high limit is to be read.
and InOut

DIM

Input

UDINT

I, Q, M, D, L or
constant

Dimension of the ARRAY of
which the variable high limit
is to be read.

OUT

Output

DINT

I, Q, M, D, L

Result

You can find additional information on valid data types under "Data types (Page 125)":

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Example
In the function (FC) block interface, the input parameter ARRAY_A is a one-dimensional
array with variable dimensions.

If the "Enable_Start" operand returns signal state "1", the CPU executes the instruction. It
reads out the variable high limit of the ARRAY #ARRAY_A from the one-dimensional array. If
the instruction executes without errors, it sets operand "Enable_Out" and sets the "Result"
operand.

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8.6.8

Read / Write memory instructions

8.6.8.1

PEEK and POKE (SCL only)
SCL provides PEEK and POKE instructions that allow you to read from or write to data
blocks, I/O, or memory. You provide parameters for specific byte offsets or bit offsets for the
operation.
Note
To use the PEEK and POKE instructions with data blocks, you must use standard (not
optimized) data blocks. Also note that the PEEK and POKE instructions merely transfer data.
They have no knowledge of data types at the addresses.

PEEK(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_);

Reads the byte referenced by byteOffset of
the referenced data block, I/O or memory
area.
Example referencing data block:

%MB100 := PEEK(area:=16#84,
dbNumber:=1, byteOffset:=#i);

Example referencing IB3 input:

PEEK_WORD(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_);

%MB100 := PEEK(area:=16#81,
dbNumber:=0, byteOffset:=#i); // when
#i = 3

Reads the word referenced by byteOffset of
the referenced data block, I/O or memory
area.
Example:

PEEK_DWORD(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_);

%MW200 := PEEK_WORD(area:=16#84,
dbNumber:=1, byteOffset:=#i);

Reads the double word referenced by
byteOffset of the referenced data block, I/O or
memory area.
Example:

PEEK_BOOL(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_,
bitOffset:=_in_);

%MD300 := PEEK_DWORD(area:=16#84,
dbNumber:=1, byteOffset:=#i);

Reads a Boolean referenced by the bitOffset
and byteOffset of the referenced data block,
I/O or memory area
Example:

%MB100.0 := PEEK_BOOL(area:=16#84,
dbNumber:=1, byteOffset:=#ii,
bitOffset:=#j);

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POKE(area:=_in_,
dbNumber:=_in_,
byteOffset:=_in_,
value:=_in_);