Motorola Solutions 89FT4839 Moscad-L P44-UHF FLN5923A, SCADA Terminal User Manual Chapter Error

Motorola Solutions, Inc. Moscad-L P44-UHF FLN5923A, SCADA Terminal Chapter Error

programmers manual

ToolBox for MOSCAD RTUsFor Programming ToolBox Version 7.51 Motorola Inc.1999All rights reservedSystem Overview68P02956C45-A
COMMERCIAL WARRANTY (STANDARD)Motorola radio communications products are warranted to be free from defects in material and workmanship for aperiod of ONE (1) YEAR, (except for crystals and channel elements which are warranted for a period of ten (10) years),from the date of shipment. Parts, including crystals and channel elements, will be replaced free of charge for the fullwarranty period but the labor to replace defective parts will only be provided for one Hundred-Twenty (120) days fromthe date of shipment. Thereafter purchaser must pay for the labor involved in repairing the product or replacing theparts at the prevailing rates together with any transportation charges to or from the place where warranty service isprovided. This express warranty is extended by Motorola Communications and Electronics Inc., 1301 E. AlgonquinRoad, Schaumburg, Illinois 60196, to the original purchaser only, and only to those purchasing for purpose of leasing orsolely for commercial, industrial, or governmental use.THIS WARRANTY IS GIVEN IN LIEU OF ALL OTHER WARRANTIES EXPRESS OR IMPLIED WHICH ARESPECIFICALLY EXCLUDED, INCLUDING WARRANTIES OF MERCHANTABILITY OR FITNESS FOR APARTICULAR PURPOSE. IN NO EVENT SHALL MOTOROLA BE LIABLE FOR INCIDENTAL OR CONSEQUENTIALDAMAGES TO THE FULL EXTENT SUCH MAY BE DISCLAIMED BY LAW.In the event of a defect, malfunction or failure to conform to specifications established by seller, or if appropriate, tospecifications accepted by Seller in writing, during the period shown, Motorola, at its option, will either repair or replacethe product or refund the purchase price thereof, and such action on the part of Motorola shall be the full extent ofMotorola’s liability hereunder.This warranty is void if:a. the product is used in other than its normal and customary manner;b. the product has been subject to misuse, accident neglect or damage;c. unauthorized alterations or repairs have been made, or unapproved parts used in the equipment.This warranty extends only to individual products, batteries are excluded, but carry their own separate limited warranty.Because each radio system is unique, Motorola disclaims liability for range, coverage, or operation of the system as awhole under this warranty except by a separate written agreement signed by an officer of Motorola.Non-Motorola manufactured products are excluded from this warranty, but subject to the warranty provided by theirmanufacturers, a copy of which will be supplied to you on specific written request.In order to obtain performance of this warranty, purchaser must contact its Motorola salesperson or Motorola at theaddress first above shown, attention Quality Assurance Department.This warranty applies only within the United States.COMPUTER SOFTWARE COPYRIGHTSThe Motorola products described in this instruction manual may include copyrighted Motorola computer programsstored in semi conductor memories or other media. Laws in the United States and other countries preserve for Motorolacertain exclusive rights for copyrighted computer programs including the exclusive right to copy or reproduce in anyform the copyrighted computer program. Accordingly, any copyrighted Motorola computer programs contained in theMotorola products described in this instruction manual may not be copied or reproduced in any manner without theexpress written permission of Motorola. Furthermore, the purchase of Motorola products shall not be deemed to granteither directly or by implication, estoppel, or otherwise, any license under the copyrights, patents or patent applicationsof Motorola, except for the normal non-exclusive, royalty free license to use that arises by operation of law in the sale ofa product.
iTable of ContentsGENERAL ..............................................................................................................................................................IIIGlossary ...........................................................................................................................................................iiiTerms and Conventions....................................................................................................................................viMOSCAD RTU And ToolBox Software Version Policy ...................................................................................viiApplicable Documentation...............................................................................................................................viiiModel Complements.........................................................................................................................................ixOptions.............................................................................................................................................................xAccessories.......................................................................................................................................................xiTHE MOSCAD SYSTEM -OVERVIEW...................................................................................................................1The MOSCAD System ......................................................................................................................................1Control Center .............................................................................................................................................................. 1Remote Terminal Unit (RTU)....................................................................................................................................... 2Communication Processor/MODBUS (MCP-M) ......................................................................................................... 2Communication Processor/TCP/IP (MCP-T)................................................................................................................ 2ToolBox for MOSCAD RTUs ...........................................................................................................................3Features and Functions ................................................................................................................................................. 3The RTU Programming Concept.................................................................................................................................. 3Programming Sequence ................................................................................................................................................ 4RTU Definition............................................................................................................................................................. 4Communication Network..................................................................................................................................6The RTUs and the Network.......................................................................................................................................... 7Communication Links................................................................................................................................................... 7Communication Types.................................................................................................................................................. 7Network Configurations ............................................................................................................................................... 8Starting a ToolBox Application........................................................................................................................15Entering the Password .................................................................................................................................................. 15Changing the Session Password.................................................................................................................................... 15THE TOOLBOX FOR MOSCAD RTUS...................................................................................................................16Hardware and Software Requirements ............................................................................................................16Installing ToolBox............................................................................................................................................16Connecting ToolBox to RTU ............................................................................................................................16A Brief Tour .....................................................................................................................................................16The RTU....................................................................................................................................................................... 16Database Principles....................................................................................................................................................... 18Programming Philosophy.............................................................................................................................................. 20The Tools..........................................................................................................................................................22Site Configuration (MOSCAD-L)................................................................................................................................. 23Network Configuration................................................................................................................................................. 25Application Programmer .................................................................................................................................26Database Builder........................................................................................................................................................... 28Process Programming ................................................................................................................................................... 28I/O Link ........................................................................................................................................................................ 29Compiler....................................................................................................................................................................... 30Downloading and Monitoring....................................................................................................................................... 31REMOTE TERMINAL UNIT......................................................................................................................................32The RTU Hardware..........................................................................................................................................32
iiCPU Module................................................................................................................................................................. 32I/O Modules.................................................................................................................................................................. 38RTU Software...................................................................................................................................................38MDLC COMMUNICATION PROTOCOL ...................................................................................................................40Physical Layer..................................................................................................................................................41Link Layer ........................................................................................................................................................41Network Layer..................................................................................................................................................42Transportation Layer .......................................................................................................................................42Session Layer ...................................................................................................................................................42Presentation Layer...........................................................................................................................................43Application Layer.............................................................................................................................................43
iiiGeneralGlossaryThis list of terms consists of abbreviations, acronyms and specialized words used in thismanual.Acronyms and AbbreviationsACK AcknowledgeAGA American Gas AssociationASL Arithmetical Shift to LeftASR Arithmetical Shift to RightBCD Convert to BCD FormatBIN Convert to Binary FormatCD Carrier DetectCOS Change of StateCPU Central Processing UnitCPY CopyCRC Cyclic Redundancy CheckCTD Count DownCTS Clear to SendCTU Count UpDBB Data Base BuilderDCE Data Communication EquipmentDFM Direct Frequency ModulationDOF Delay OffDON Delay OnDPL Digital Private LineDPSK Differential Phase Shift KeyingDSP Digital Signal ProcessingDSR Data Set ReadyDTE Data Terminal EquipmentDTR Data ReadyEGU Engineering UnitsFEP Front End Processor (MCP-M, MCP-T, or FIU)FIU Field Interface UnitFSK Frequency Shift KeyingGND GroundGPS Global Positioning SystemHDLC High -level Data Link CommunicationHW HardwareI/O Input/OutputIGC/M IBM Graphic Center for MOSCAD (old)IMP Integrated Multiprotocol ProcessorINTRAC Two-layer (32 bits) protocol
GeneralivJMP JumpJSP Jump To SubprocessLED Light Emitting DiodeLSL Shift to LeftLSR Shift to RightMCP-M Motorola Communication Processor – MODBUSMCP-T Motorola Communication Processor – TCP/IPMDLC MDLC Motorola Data Link Communication (Seven-layer OSI protocol)MEIC Previous generation RTU typeMMI Man Machine InterfaceMODBUS MODICON BUS ProtocolMOSCAD Motorola SCADAMOSCAD-L Motorola SCADA-LightMOVE Move ValueMOVH Move HighMTE Multi Task EnvironmentNACK Negative AcknowledgeN.C. Normally ClosedN.O. Normally OpenNEMA National Electrical Manufacturers Association (issues enclosurestandards)OSI Open System InterconnectionOVF OverflowPC Personal ComputerPID Proportional Integral DerivativePL Private LinePLC Programmable Logic ControllerPPH Pulse per HourPPS Pulse per SecondPSTN Public Switching Telephone NetworkPTT PushtoTalk(buttononradio)RAM Random Access MemoryRET ReturnRF Radio FrequencyROM Read Only MemoryROR Rotate to RightRNR Receive, Not ReadyRR Receive, ReadyRST ResetRTS Request to SendRTU Remote Terminal Unit (can be MOSCAD or MOSCAD-L)RUNP Run ProcessRX ReceiveSCADA Supervisory Control and Data AcquisitionSW SoftwareTDPSK Trunked Differential Phase Shift Keying
GeneralvTRT Retentive TimerTX TransmitUART Universal Asynchronous Receiver TransmitterUCL User Call FunctionUDF UnderflowXTAL CrystalDefinitionsUpload Load a block of data or code, from the RTU to the ToolBoxDownload Load a block of data or code, from the ToolBox to the RTU.
GeneralviTerms and ConventionsThe MOSCAD RTU is shipped in two versions, MOSCAD RTU and MOSCAD-L RTU.Most of the features described in the MOSCAD documentation are common to MOSCADand MOSCAD-L. Throughout the documentation the terms “RTU” and “MOSCAD” referto the “generic” system. Differences are indicated by specific references to MOSCAD andMOSCAD-L.RTUs and MCP/Ms are “sites”. In the MOSCAD documentation, references to “site”generally mean “RTU” and vice-versa. The MCP/M is a central adapter between SCADAand the field.The MOSCAD ToolBox package consists of several Windows 95/NT applications, such asSite Configuration and Application Programmer. Throughout the MOSCADdocumentation the application names are printed in initial capitals.Some features are valid from a certain version of Programming ToolBox. as specifiedusing the ≥Va.b notation. See MOSCAD RTU And ToolBox Software Version Policy.
GeneralviiMOSCAD RTU And ToolBox Software Version PolicyThe version numbers of the Programming ToolBox and MOSCAD RTU system softwareare updated according to additional features and improvements.Compatibility (at source level) between the Programming ToolBox and the MOSCADRTU is assured only if the version number of the Programming ToolBox Software is laterthan the version number of the MOSCAD RTU system software.A version number is composed of two numbers, as in the following example: V1.61. Theone-digit number to the left of the decimal point describes a major modification of thesoftware, while the two-digit number to the right of the decimal point describes a minormodification.In this manual, some headings of major subjects are marked by the following annotation:≥Va.b.For example, ≥V1.61 indicates that the marked subject is supported by an RTU whoseMOSCAD software version number is at least 1.61.This numbering convention applies to MOSCAD-L as well, except for the versions below:If no version number is specified, then that feature is supported by all versions ofMOSCAD and MOSCAD-L.MOSCAD-L Version Supported byToolBox Version1.0x 5.012.0x 6.002.40 6.50
GeneralviiiApplicable DocumentationThe MOSCAD system includes the following manuals:•ToolBox for MOSCAD RTUs, MOSCAD Programming ToolBox - Overview,Motorola publication no. 68P02956C45•ToolBox for MOSCAD RTUs, MOSCAD Programming ToolBox - System Setup &Diagnostic Tools, Motorola publication no. 68P02956C50•ToolBox for MOSCAD RTUs, MOSCAD Programming ToolBox - ApplicationProgrammer, Motorola publication no. 68P02956C55•ToolBox for MOSCAD RTUs, MOSCAD Programming ToolBox - Third PartyProtocols Support, Modbus and Allen Bradley,Motorola publication no. 68P02956C70•ToolBox for MOSCAD RTUs, MOSCAD Programming ToolBox C Toolkit,Motorola publication no. 68P02956C75•ToolBox for MOSCAD RTUs, MOSCAD Programming ToolBox - AGA8 Gas FlowCalculations, Motorola publication no. 68P02957C10•MOSCAD RTU Service manual,Motorola publication no. 68P02991G90•MOSCAD RTU Owner's manual,Motorola publication no. 68P02994G10•MCP/M User’s Manual, Motorola publication no. 68P02945C05-0.
GeneralixModel ComplementsF2316 MOSCAD Programming ToolBoxFVN4126 Program Software Package on CD-ROM + ManualsFLN6457 RS232 Terminal Adapter Cable + Adapters
GeneralxOptionsV377 Third Party ProtocolsFVN4119 Third Party ProtocolsV378 AC Analyzer ToolkitFVN 4335 AC Analyzer ToolkitV284 AGA8 Gas Flow CalculationsFVN 4334 AGA8 Gas Flow CalculationsV212 Master Key DisketteFVN 4396 Master Key DisketteV385 X.25 option for ToolBoxFVN 4730 X.25 option for ToolBoxV204 MDLC over IP option for ToolBoxFVN 4782 MDLC over IP option for ToolBox
GeneralxiAccessoriesFVN1710 Upgrade ToolBoxFVN4126 Program Software Package on CD-ROM + ManualsFVN4334 AGA8 Gas Flow Calculations + ManualFVN4119 Third Party ProtocolsFVN4335 AC Analyzer ToolkitFVN4396 Master Key DisketteFLN2391 “C” Toolkit Package + Manual
1The MOSCAD System - OverviewMOSCAD Programming ToolBox is a package of computer programs that buildssophisticated distributed SCADA (Supervisory Control and Data Acquisition) systemsfor a wide range of applications.The MOSCAD (Motorola SCADA) system consists of remote terminal units (RTU)and one or more computerized control centers, connected to a communication networkvia the Communication Processor/TCP/IP (MCP-T) or the CommunicationProcessor/MODBUS (MCP-M). The Programming ToolBox software package runson a Pentium 100 (or more powerful) computer.The main function of the Programming ToolBox is to define and maintain theMOSCAD system according to user needs and requirements.The Programming ToolBox also enables the engineer to program/download theapplication program to be executed in the RTU and to perform debugging in eachRTU, using a symbolic (graphic) debugging tool. The Programming ToolBox may beoperated either locally by direct connection to the selected unit’s computer port, orremotely, by connection to a computer port of any other RTU in the system (MCP-M,MCP-T, or RTU) via the system communication network.By connecting the Programming ToolBox to a computer port of one of the RTUs,MCP-Ms, or MCP-Ts in the system, you can program or service that specific RTU orany other RTU in the system.The MOSCAD SystemThe entire control system is comprised of the SCADA central computer as a masterstation, communicating with RTUs over various communication links, such asconventional radio, trunked radio, microwave, wireline, or dial system (telephone).The communication system is used for transmitting alarms, status information,telemetric readings, calculated data, diagnostics, and error logging information fromthe RTUs to the central facility computer and vice versa. It is also used fordownloading, monitoring, and debugging the application program at the site.The system can be relatively simple, comprising several RTUs and a control center, ora more complicated hierarchical system, where several sub-centrals communicate withlower, parallel and higher hierarchies. The RTUs may also communicate with eachother and/or with any other hierarchy in the system.Control CenterThe control center computer, with the user interface, provides the user with fullgraphic control of the RTUs’ operation, including database and parameter changes,and on-line application monitoring for the system engineer. The central computer andMCP-M communicate using the MODBUS protocol; MCP-T uses the TCP/IPprotocol.
The MOSCAD System - Overview2One of the functions of the control center is to exchange data with the RTUs. It mayinterrogate the RTUs for any portion of their database. Multiple interrogation(polling) cycles operate with different priorities and by different trigger mechanisms(time or events).Remote Terminal Unit (RTU)The RTU is a smart modular unit designed to operate as a stand-alone controller or aspart of a system having any number of RTUs, control centers, and sub-centralsconnected through a communication network with any number of links and nodes.The RTU is configured and loaded with the appropriate application using theProgramming ToolBox.The RTU is a microprocessor-based unit, which consists of a CPU module and variousI/O and communication modules. The very wide range of I/O and communicationmodules makes the MOSCAD system flexible to satisfy any application requirements.MOSCAD-L, on the other hand, is a lighter version with a limited number of I/Omodules and fewer features.The MCP-M and the RTUs communicate using the MDLC protocol, based on theseven layers of the OSI (Open Systems Interconnection) model published by ISO, andadapted for SCADA communications. The protocol provides network support andmultiple logical channels per physical port, enabling simultaneous central-to-RTU andRTU-to-RTU sessions. It also enables each RTU to simultaneously run severalcommunication sessions, such as data exchange, on-line monitoring, diagnostics, etc.The RTU is discussed in more detail later in this manual. For technical information,consult the Owner’s manual and the Service manual.Note that throughout the ToolBox documentation, the terms RTU and unit are usedinterchangeably.Communication Processor/MODBUS (MCP-M)The MCP-M is an intelligent, intermediary unit that ensures communications betweenthe control center and the RTUs. Its pre-loaded application and database allow it toperform tasks independently, at times when the control center is not active. The MCP-M application and database are dedicated to collecting data from the field andperforming scheduling tasks.The MCP-M is installed in the control center and does not require any furtherprogramming: the user only customizes the unit by setting parameters. It can beconfigured using a ToolBox of its own, which differs from the ToolBox for RTUscovered in this manual.The communication processor does not have independent I/O capabilities. Any datacollection and assessment needs that may arise in the control center premises are metby an additional RTU that is connected to the network like any remote terminal on thefield.
The MOSCAD System - Overview3Communication Processor/TCP/IP (MCP-T)The MCP-T replaces the MCP-M where only a router that converts TCP/IP (overEthernet) to MDLC and vice versa, is needed. Unlike MCP-M, it does not have adatabase or any control capabilities.ToolBox for MOSCAD RTUsThis section is a brief review of Programming ToolBox, the software package used toconfigure an RTU system and to build an application.Features and FunctionsThe following are the main features of the Programming ToolBox:•Configuring the RTU sites, configuring the network, building and maintaining theapplication database and flow•Preparing project documentation for the user•Automatically creating a “central file” to be used later during RTU databasecreation in the MCP-M.•Performing the following functions on any RTU either via local connection or viathe communication network:Downloading and uploading the site configuration and related dataDownloading the application and the network configurationDownloading and uploading the compressed sourceDownloading C blocks which are run by the applicationDownloading the phone bookDownloading the third-party protocolReal-time symbolic (graphic) monitoring and debugging of the application (bothdatabase and process)Updating the time and the date in RTU sitesTesting all hardware modules, including software calibration of analog inputs andoutputsTesting radio channelsRetrieving time-tagged events (of very high resolution) logged in the RTUsSynchronizing the system clock according to MCP-M’s or FIU’s timeRetrieving errors logged in the RTUs (hardware or software malfunctions)Capturing the data packets on the communication links and analyzing the sevenlayers of the MDLC protocolSystem software diagnostics by object entity namesThe RTU Programming ConceptThe various circles illustrated below describe the RTU in layers. The first layer is theRTU hardware that is the base for the system software and application (includingconfiguration) software. When the application software runs, the RTU database isupdated.
The MOSCAD System - Overview4The following figure shows different ways of accessing and modifying each of theRTU layers, using the Programming ToolBox:•Locally by direct connection to the RTU•Remotely via the communication networkDiagnostics/DebuggingLocal ProgrammingDownload/Upload/MonitorDownload/MonitororRTUMCP/MRemoteProgrammingRemoteProgrammingAPPLICATIONDATA BASEAPPLICATIONSOFTWARESYSTEMSOFTWAREHARDWARE(CPU, COMM,I/O MODULES)RTUCONTROLCENTERPROGRAMMINGTOOL BOXPROGRAMMINGTOOL BOXDiagnosticsProgramming SequenceThe definition of the RTU application allows the system engineer to build a databaseas a set of tables. The tables used for the RTU database definition are the basis forprocess programming, I/O link definition, automatic central database definition, real-time monitoring of the RTU’s operation, etc.Once the database is built, the RTU application is created using the symbolic MotorolaAdvanced Ladder Diagram Language. These symbolic definitions are later used formonitoring and debugging.The necessary RTU application documentation is automatically produced, includingautomatic insertion of notes into the produced documents.After downloading the application to the RTU, the control program of the terminalcontrols the RTU run-time operations. The Programming ToolBox terminal thenallows the system engineer to perform any required operation.RTU DefinitionThe RTU definition is carried out in three stages, stored as corresponding sections inthe RTU:•Site configuration - defining the I/O modules mounted on the RTU, the unit’s ports,and the site address.•Network configuration - for defining the communications network structure.•Application program - building the application database and flow.
The MOSCAD System - Overview5Site ConfigurationThe MOSCAD system operates with a very wide range of I/O modules and interfacecommunication boards which satisfy any application requirements. The siteconfiguration includes the definition of:•The I/O modules mounted on the RTU and their location in the various racks•The ports of the RTU and their parameters•Site ID (logical address) and system address.Since several RTUs in the system usually have the same configuration (except for thelogical address), you save the configuration to a file. Then, you can download thesame configuration to different RTUs, adding only their logical address and systemaddress.Once the configuration is downloaded to the site, it is ready to receive the userapplication program. The site configuration must be defined and downloaded to theRTU before downloading the application.The file created by Site Configuration is later used by Application Programmer duringI/O Link definition function (I/O assignment). Full details can be found in theApplication Programmer manual.Network ConfigurationThe Network Configuration application is designed to define the communicationnodes in the network. The program determines the network structure - there is no needto define all RTUs, only the nodes in the network. The MDLC protocol uses thesedefinitions for the automatic routing of the packets through the network.Network configuration is needed only in MOSCAD systems that use more than onecommunication link. A simple network, such as one MCP-M connected to onecommunication link, does not require network configuration.Like site configuration, the network configuration parameters can be saved to a file.These parameters can be downloaded using Network Configuration or can beautomatically loaded into the RTUs with the application. During application loading,the user is asked to provide the network configuration name, the site ID, and one linkID of the destination RTU.The same network configuration file is used for all the sites in the system and may alsobe used in other systems (with the same structure).Note: The network configuration must be loaded to all sites in the system (includingsite nodes) to enable each site to route the packets through the network.
The MOSCAD System - Overview6RTU ApplicationThe RTU application is the control process to be executed by the remote terminal.The application definition consists of the following:•RTU database•The process to be performed by the RTU (in the form of rungs, using the MotorolaLadder Diagram Language and C functions)•The connections between the database and the various inputs and outputs of the I/Omodules (I/O link). The I/O link portion of the RTU application is based on thedefinition of the RTU I/O modules as determined in the site configuration.The RTU database is divided into reserved variables or constants, retrieved from awide bank of system information (such as functional variables, reserved flags ortemporary buffers), and user variables or constants, arranged according to various datatypes (such as discrete inputs/outputs, value inputs/outputs, timers, parameters,integer/real values, etc.). User variables, in most cases, represent the actualinputs/outputs from/to the outside world. They are designed to monitor and controlthe user devices connected to the appropriate RTUs. They may also be used torepresent internal inputs/outputs for intermediate results and time elements, or toperform various calculations.The application database is built as a set of tables, where tables define a group ofdevices. Each row defines a separate device, and each column contains device-specific data. The table entries are assigned user-significant names, such as PUMP1.During program execution, the process continuously updates the database according tothe following:•RTU physical inputs/outputs incoming information•Internal data stored in the RTU memory•Data received via the communication channel and the communication ports.DownloadingThe downloading to the RTU is performed in the following order:•Site configuration•RTU application (and/or network configuration) according to the configurationdefinition.•Additional optional blocks, such as: Phone book, “C” blocks, special drivers(MODBUS, AGA8, DNP3, etc.)Communication NetworkThe MOSCAD system network consists of RTUs communicating with one or morecomputerized control centers and/or with other RTUs. Each control center isconnected to the communication network via the MCP-M or MCP-T.The system can be relatively simple, comprising several RTUs and one control center.It can be modularly expanded to a more hierarchical system, where several sub-
The MOSCAD System - Overview7systems (comprising intelligent RTUs and/or sub-centrals controlling their peripheralRTUs) communicate with a central computer.The communication network is flexible, enabling each RTU to communicate withhierarchies above it (RTU-to-central), parallel to it (RTU-to-RTU), under it (anotherRTU), and also relaying messages through it (when the RTU serves as acommunication node).While the communication protocol allows for a complex hierarchical system structure,it does not make it complicated. This is because most of the communicationinteractions are transparent to the user, except in those cases where the communicationis to be defined by the ladder application. In such cases, you should perform simpleprogramming operations to configure the required application.The RTUs and the NetworkEach RTU may be configured to serve as a far-end terminal or as a regional center.The RTU may function as a regional center either by definition or only after loss ofcommunication with the central. It also can act as a communication node (aninterconnection point between two or more different links) while performing its othertasks.The RTU network uses the MDLC protocol, which incorporates all seven layers of theOSI model adapted for SCADA. It supports multiple logical channels per physicalport, enabling simultaneous central-to-RTU and RTU-to-RTU sessions. It also enableseach RTU to simultaneously run several kinds of communication applications, such asreporting alarms by contention, on-line monitoring, performing diagnostics checks,etc. The MDLC protocol is discussed later in this manual.The Programming ToolBox may perform monitoring, modification, diagnostics, errorlogging, etc., on any RTU in the system from any RS232 port in the system,configured as either RS232 Local Computer port or RTU-to-RTU RS232 (RS-link1 –RS-link19).Communication LinksThe system may support a network comprised of a nearly unlimited number of links.The RTU supports a variety of communication media and baud rates, as detailedbelow:•Through the radio/wireline communication port:Direct FM (DFM) modem on conventional radio, up to 4800 bpsFSK modem on conventional radio, up to 2400 bpsFSK modem on trunked radio, up to 2400 bpsWireline, up to 19200 bps, using external modemsWireline, up to 2400 bps, using built-in modemsDial-up, up to 2400 bps, using built-in modemsExternal Dial-up modem•Through the RS-232-C and RS-485 communication ports, up to 19200 bps.The communication via the various ports may be simultaneous.
The MOSCAD System - Overview8The RTU operates on all radio frequencies: VHF 136-174 MHz, UHF 403-430 and450-470 MHz, 900 MHz band, 800/900 MHz trunking and microwave.The RTU contains a circuit for monitoring activity on the radio or linecommunications channel. Channel access software prevents the RTU fromtransmitting over a busy channel. Transmission is inhibited until the channel is free.There are also several priority levels for getting to the channel when it becomesavailable.Communication TypesTheRTUsinthesystemarelinkedtoaradioorwirelinenetworkasdefinedbythesystem engineer, according to user requirements. Each RTU executes its applicationand, simultaneously, supports the communications link (or links) defined for it, andserves as a network node, if so defined.The MOSCAD system supports up to 29 wireline links (LINE 1 to LINE 29), up tonine radio links (RADIO 1 to RADIO 9), and up to 19 local RTU-to-RTU links (RS-link 1 to RS-link 19) that use RS232. Any of the radios may be either conventional ortrunked. Computers may be connected to the ports configured as RS232 LocalComputer or as local RTU-to-RTU link.For conventional radios, up to nine zones can be defined on every frequency (of thenine supported frequencies). A radio link for conventional radios is divided into zoneswhen not all sites can communicate with each other and F1/F2 repeaters (using twofrequencies) are not to be used. In this case, some RTUs will serve as Store &Forward repeaters and the link is divided into zones.A zone is defined as a group of one or more sites that can directly communicate witheach other without a Store & Forward repeater. The name of a zone is composed ofthe link name and the zone number. For example, for RADIO 3 zone number 1 isnamed RADIO 3/1, zone number 2 - RADIO 3/2 and so on.After defining the communications network, the user must define the various linksused in the system as well as the RTUs that serve as nodes between the links. Anetwork node is an RTU that functions as an interconnection point between two ormore different links. A Store & Forward node, on the other hand, is a network node,which relays messages using the same physical port.Network ConfigurationsThe MOSCAD system supports both simple and complex communication networks.The following sections describe various configurations from different aspects.Simple SystemA simple system, comprised of a central computer, MCP-M, and RTUs connected overone communication link, is shown in the following figure:
The MOSCAD System - Overview9ProgrammingToolboxMCP/MCentralComputerProgrammingToolboxRTU 1RTU 2RTU 3RS-232CRadio link (RADIO 1)The Programming ToolBox may be connected to any port of the RTU or MCP-Mconfigured as a computer port.The radio link, named RADIO 1 in the above figure, can be a conventional radio usingDFM (Direct Frequency Modulation) or FSK (Frequency Shift Keying) radio modems,or a trunked radio using FSK radio modem.The ports of the RTUs and MCP-M should be defined via Site Configuration. Thelogical name (in this case, RADIO 1) of the communication link is also defined. Asnetworks involve at least two types of links, simple systems do not need to beconfigured as networks.Two-Link and Multiple Link SystemsA two-link system utilizing a communications network, comprised of twocommunication links, is described in the following figure:MCP/MCentralComputerRTU 4RTU 5RTU 6RS-232CRADIO 1RTU 1RTU 2RTU 3LINE 1The MCP-M in the system illustrated above serves as a network node between linkRADIO 1 and link LINE 1. Configuring the MCP-M to have access to two differentlinks enables the MCP-M to serve as a node between these links.The MDLC protocol permits RTU-to-RTU communications without the interventionof the central computer. RTUs that are not on the same link communicate with eachother via the network node (in this case, the MCP-M).
The MOSCAD System - Overview10A multi-link system is a network that uses several link types. The following figureillustrates a system where a third link type, RADIO 3, connects an RTU to anotherterminal that communicates over RADIO 2. RTUs connected to the RADIO 1 link canreach RTU 7 via MCP-M and then RADIO 2.MCP/MCentralComputerRTU 4RTU 5RTU 6RS-232CRADIO 1RTU 1RTU 2RTU 3RADIO 2RTU 7RADIO 3Two-Zone SystemA two-zone system that uses conventional radio over a single frequency is described inthe following figure:ZONE 2MCP/MRTU 9RTU 2RTU 1RTU 3ZONE 1RTU 4RTU 5RTU 6Store & ForwardRTU 9 (Site ID = 9) is configured as a Store & Forward repeater. It performs dataexchange between units that operate on the same frequency but are unable tocommunicate directly for reasons of path and propagation. Any RTU in zone 1 maycommunicate with any RTU in zone 2 via this repeater.The figure below illustrates this system schematically. In this case, RTU 9 is anetwork node between the RADIO 1/1 and RADIO 1/2 links. The network software
The MOSCAD System - Overview11treats the Store & Forward node as it treats the node between line and radio: logicallythe links appear as two different links, but physically they share the same port.MCP/MRTU 1RTU 2RTU 4RADIO 1/1RTU 3RTU 9RADIO 1/2Using Site Configuration, the MCP-M and the RTUs in zone 1 are configured to haveaccess to the RADIO 1/1 link. The RTUs in zone 2 are configured to have access tothe RADIO 1/2 link, and RTU 9, the network node, is configured to have access toboth RADIO 1/1 and RADIO 1/2 links.Using Network Configuration, RTU 9 is configured as the only node in the network.This terminal is configured to have two links, RADIO 1/1 and RADIO 1/2.Multiple Zone SystemThe following figure illustrates a MOSCAD system spanning multiple zones.ZONE 2MCP/MRTU 40RTU 15RTU 2RTU 1RTU 3ZONE 1RTU 4RTU 5RTU 6The schematic representation of this system is shown below. The system assumes thatthe two nodes, RTU 15 and RTU 40, cannot “hear” each other. They communicate viathe MCP-M, which is also a Store & Forward node. This system, therefore, consistsof four zones and three nodes (RTU 15, RTU 40, and MCP-M). Any communicationbetween RTUs in different zones passes through these three nodes.MCP/MRTU 1RTU 2RADIO 1/3RTU 15RTU 1RTU 2RADIO 1/2RADIO 1/1RADIO 1/4RTU 40
The MOSCAD System - Overview12In the above situation, three nodes with their accessible (logical) links should bedefined, using Network Configuration.Using Site Configuration, the RTUs in zone 1 should be configured to have access tothe RADIO 1/1 link, and the RTUs in zone 2 to the RADIO 1/2 link.RTU 15 should be configured to have access to both RADIO 1/1 and RADIO 1/3links, while RTU 40 should be configured to have access to both RADIO 1/2 andRADIO 1/4 links.The MCP-M is configured to have access to both RADIO 1/3 and RADIO 1/4 links.Assuming that the two nodes (RTU 15 and RTU 40) can “hear” each other, the resultis a system consisting of three zones and two nodes, as shown in the following figure:MCP/MRTU 1RTU 2RADIO 1/3RTU 15RTU 4RTU 5RADIO 1/2RADIO 1/1RTU 40In this case, the two nodes do not communicate through the MCP-M. Therefore, theMCP-M does not serve as a node in the system. Note that the communication betweenRTUs in different zones passes only through two nodes.Dual Dial Port(MOSCAD version ≥V3.70, MOSCAD-L version ≥V1.00)The CPU supports two dial links at Port2 and Port3. Port2 may be connected to anexternal AT modem and Port3 may be connected to either an external AT modem, orto an internal modem configured at dial option.Prior to using an external modem, emulate an external terminal using a PC and anystandard communication program, and set its parameters as follows:•9600 bps (for example)•8 bits•no parity•1stopbitEnter the modem telephone numbers into the MOSCAD Phone Book utility. If yourtelephone works either in a pulse or in a tone mode, it is recommended to add theletter P(pulse) or T (tone) in front of the telephone number.If you are using an external modem, set its configuration according to the followinglist.
The MOSCAD System - Overview13Action CommandDisable off-line echoing ATE0Enable audio messages ATV1Disable quiet mode (The status codes are sent tothe terminal.) ATQ0Enable all codes ATX4Enable carrier detect when a connection isestablished. AT&C1You may enter the commands in one string, ATE0V1Q0X4&CI&W, where &Wimplies saving the above parameters for the next power-up.When several RTUs are connected to the PSTN (Public Switching TelephoneNetwork), as illustrated below, several configurations are viable as described in theexamples that follow.EXTERNALMODEM ATPORT 2RTU 4 RTU 5RTU 3RTU 2RTU 1EXTERNAL MODEMAT PORT 2 EXTERNAL MODEMAT PORT 3INTERNAL MODEMAT PORT 3EXTERNALMODEM ATPORT 3INTERNALMODEM ATPORT 3EXTERNALMODEM ATPORT 2PSTNNote that in the illustrated configurations, as in all the connections over the PSTN,there is only one link ID. It is the responsibility of the software to decide which line todial. When two lines are available, the Port 2 line has priority.1. To communicate between RTU 1 and RTU 2:•Configure RTU 1 Port 2 as external modem.•Update the RTU 2 telephone number.•Any transmission from RTU 1 to RTU 2 will cause automatic dialing.As the connection is established, information will be transferred fromone modem to the other. When no information is transferred for aperiod longer than the “Hanging up an unused line by INITIATORafter...” Advanced Physical Layer parameter, the line will bedisconnected.
The MOSCAD System - Overview142. To communicate between RTU 1 and RTU 4:•Configure RTU 1 Port 2 as external modem.•Update the two RTU 4 telephone numbers.•Any transmission from RTU 1 to RTU 4 will cause automatic dialingto the first number in the phone book. If the first number is busy, orthere is no answer, the second number is automatically dialed. As theconnection is established, information will be transferred from onemodem to the other. When no information is transferred for a periodlonger than the “Hanging up an unused line by INITIATOR after...”Advanced Physical Layer parameter, the line will be disconnected.3. To communicate between RTU 4, RTU 5, and RTU 3 simultaneously:•Configure RTU 4 Port 2 as external modem and RTU 4 Port 3 asinternal modem dial-up, Auto Answer & Dial.•Update the two RTU 5 telephone numbers and the RTU 3 telephonenumber.•Any transmission from RTU 4 to RTU 5 will cause automatic dialingfrom the first available port (when both ports are available, Port 2 ischosen) to the first number on the list. If the first number is busy, orthere is no answer, the second number is automatically dialed. As theconnection is established, information will be transferred from onemodem to the other. When no information is transferred for a periodlonger than the “Hanging up an unused line by INITIATOR after...”Advanced Physical Layer parameter, the line will be disconnected.•AnytransmissionfromRTU4toRTU3whileRTU4andRTU5areconnected, will cause automatic dialing from Port 3. If RTU 4 andRTU 5 are disconnected, then Port 2 will be selected for dialing.
The MOSCAD System - Overview15Starting a ToolBox ApplicationToolBox consists of different Windows applications. Each application is activated viaan icon included in the ToolBox program folder.Entering the PasswordWhen a ToolBox application is activated at the beginning of a work session, ToolBoxdisplays the Password window, where the password is entered and OK is clicked.(See The Tools in the The ToolBox for MOSCAD RTUs section of this manual.)This operation activates the communication driver and the password remains in forcethroughout the session. If you want to access an RTU that requires a differentpassword, you must stop the communication driver first. See Changing the SessionPassword below.Changing the Session PasswordTo access an RTU that requires a different password, close all ToolBox tools and thendouble-click the Stop Communication Driver application icon in the ToolBox programfolder. Then, activate the ToolBox application you want and enter the password.!WARNINGIf you try to stop the communication driver while a communication session isin progress, a message warns you that a logical channel is currently open. Ifyou chose to continue (stop the driver), the results of the currentcommunication cannot be predicted. It is advisable to finish the current taskandthentostopthedriver.
16The ToolBox for MOSCAD RTUsMOSCAD ToolBox is a set of software tools designed to implement MOSCADprojects. The core of a MOSCAD project is one or more applications that reside in theRTUs that make up a MOSCAD system. ToolBox allows users of different levels andinterests to deal with different aspects of the applications. For example, theapplication developer would usually work with the ToolBox programming tools, whileother types of users would fine-tune the applications at the field, using the ToolBoxcustomization and setup tools.Hardware and Software RequirementsMOSCAD ToolBox runs on a Pentium 100 (or more powerful) computer underWindows 95 or Windows NT. It requires a minimum of 32Mb of RAM.Installing ToolBoxThe MOSCAD Programming ToolBox is installed like any other Windowsapplication. Insert the installation disk in your CD driver, activate setup.exe, andfollow installation messages and instructions. Written instructions can be found onthe leaflet attached to the CD.Connecting ToolBox to RTUThe unit (RTU) may be connected to a local computer via cable FLN6457, which endswith an adapter suitable for computer connection (25-pin female D-type connector).Any RS232 port of the RTU defined as RS232 Local Computer may be used forconnection to the Programming ToolBox. This connection provides access to thatspecific RTU, or to any other RTU in the network, to perform all the functionsdescribed in this manual.The RS232 ports default configuration of RTUs received from factory is RS232 LocalComputer (9600 baud).A Brief TourThis chapter provides a brief description of the MOSCAD/MOSCAD-Lcommunication system, and clarifies basic concepts.The RTUMOSCAD™ is the name of Motorola’s family of SCADA products. It is available ina variety of enclosures, with a multiplicity of two-way radios, and with many differenttypes of input/output (I/O) modules. A MOSCAD RTU is a remote terminal unit in aMOSCAD system.
The ToolBox for MOSCAD RTUs17Think of an RTU as a computer. It has a CPU, real-time clock, RAM and ROMmemory, serial communication ports, etc. A remote terminal unit (RTU) which isinstalled at some field location is a computer. An RTU which may act as a districtcontroller is a computer. An RTU that functions as the communications bridgebetween the radio (or other) communications system and the Master Control Center isa computer. Certainly, that Master Control Center is a computer.Just as a computer may be programmed to perform required tasks on a continuousbasis, MOSCAD is programmed in an advanced, powerful version of the ladder-logicprogramming language (and/or ‘C’). The programmed rungs are compiled into thevery same format that would be used to program an EPROM; the compiled code isdownloaded into electrically-programmed ROM within the RTU. The application, asprogrammed, may then be monitored and debugged.The following picture shows the main parts of the MOSCAD.Radio orModemBackupBatteryAC PowerSupplyCPUModuleExpansionI/O ModulesNEMAEnclosure
The ToolBox for MOSCAD RTUs18The following picture illustrates MOSCAD-L.The MOSCAD application developer need not have a degree or background incomputer science. Any programming experience in ladder-logic, Basic, Pascal or C ishelpful, but not required.Database PrinciplesAll worthwhile computer programming languages require the programmer to definethe variables before they are used. The definition includes the variable name andvariable logic type. The programming language reserves the appropriate memory forthe variable type, and can check for type mismatches as the logic statements arewritten (create an immediate error if the logic statement uses an illegal named variabletype). RTU applications must have all variables defined by name and type before theymay be used.How those named variables are organized is unconventional from a computerprogramming perspective. However, it makes perfect sense when RTU-to-RTU orRTU-to-central communications is considered.The language organizes the programming variables into collections called tables.Tables look very much like computer spreadsheets: they include many rows and mayinclude many columns. Each row and column intersection (cell) is a variable. Sometables have many rows but only one column. All the variables in a single-column tableare of the same type, i.e. all bits, all values, all digital inputs, etc. Each variable in thetable is uniquely named: PUMP1, PUMP2, etc. Such a table may contain up to 250uniquely named variables. A single-column table is illustrated below:
The ToolBox for MOSCAD RTUs19Other tables have many rows and many columns. All variable types within any columnare the same, but the several different columns may be of different variable types. Forexample, a three column table may contain one column labeled PUMP and be adigital-input type; the next column may be labeled START and be an internal valuetype; the third column may be labeled RUNTIM and be a timer type. The variablenames are a combination of the column name and the row number, i.e. PUMP,2 andSTART,4. This multiple-column table structure is particularly attractive when dealingwith dissimilar but related data, particularly as it may apply to some physical devicesuch as the pumps at a pump site. A multiple-column table may contain up to 250 rowsand up to 8 columns. Such a table is illustrated below:The programmer may create up to 127 tables of his/her own design. The design andorganization of the tables should be carefully planned. The operation of theapplication can be monitored by observing the variables; a good table design collectsrelated variables so that many different, but related, things can be observedsimultaneously.A good table design anticipates which variables must be reported to a central site, andorganizes those variables (whenever possible) into just a few tables. Understand thispart of the project, and the technical details of the applications—they are both veryimportant. Note that the protocol driver in the central has the same table structures asdo the RTUs communicating with the central. Data transfer becomes the simple taskof moving row/column data between identical tables.You, the programmer, define the variable names. You are not required to use a bit-and-register notation that reflects the electrical design of the RTU. You may defineand name your variables as you wish, with no restrictions other than name length.Even if you program in another language, the RTU system will accept your variablenames.
The ToolBox for MOSCAD RTUs20The database supports many variable (data) types. For full details, refer to theDatabase Concept chapter in the Application Programmer manual.Programming PhilosophyIn order to create an application program which meets your needs, first identify thetasks required of the program, including the information needed to complete each task(e.g. digital inputs, variables from another site, permission flags from the central, etc.).Next, sketch, in flowchart form, the logical steps required to convert the stated inputsinto the required output(s). Make sure that all combinations of inputs are properlyaddressed and lead to the correct output(s). This step is key, as it is much easier tocorrect mistakes in a flowchart on paper than to debug and correct lines ofprogramming code.All of the logic operators that are used in Basic or Pascal or C programming languagesare available to the RTU ladder-logic programmer. Only the syntax is different.Remember, the logic statements will eventually be compiled; you can’t tell how it wasprogrammed by looking at the compiled code.The operators are discussed at length in the Ladder Diagram Language chapter of theApplication Programmer manual.Ladder logic originated from the language of relays. The contacts of the relays, singlyor in combinations, appear to the left of the logic statements and constitute the tests.The coil of the relays appears to the right of the logic statement and constitutes theactions. Tests on the left, actions on the right. Line after line. The structure lookslike the rungs of a ladder, hence the name of the programming language and the name(rung) of each logic statement.The RTU implementation of ladder logic programming allows up to six lines per rung,and up to eight symbols on a single line. Therefore each RTU rung may indeed be acomplete logic statement (IF this THEN that ORIF other-this THEN other-that ELSE...).Some of the basic tests and actions are listed below.Tests (inputs)—| |— The fundamental relay contact is Normally Open; it closes when the coil isactive. There is also a Normally Closed relay contact that opens when thecoil is active. The variable name being tested must be a bit-type(not a—| / |— value-type) and appears above the symbol. These are illustrated on the left.It’s quite amazing how many decisions can be made with only these twooperators. Put them in series and you have a logical AND – see below. Putthem in parallel and you have a logical OR. You can apply Boolean logic toreduce the number of required open/close contacts, as is mandatory withhardware logic solutions. But every RTU “coil” has an unlimited numberof like-named contacts, so there is no cost incentive to minimize the numberof relay contacts. You can therefore avoid such reductions and keep thelogic readable.—| |— —| |— —| / |—……. x • • • • y••••z
The ToolBox for MOSCAD RTUs21—| < |— Ladder logic originally treated only binary data – relay contact open orclosed. Ladder logic was later modified to handle value (non-binary) data.—| = |— The variable names being tested must be value-types (not bit-types) andappear above and below the symbol. These symbols are shown at left.—| ≠ ≠ ≠ ≠ |— Testing value data has many applications. Consider some process that mustoperate if a value exceeds some setpoint.—| > |——| ↑ ↑ ↑ ↑ |— A third type of test operator is the Differentiator. It checks for a differencebetween the current and previous state of the named variable(s) that precede—| ↓ ↓ ↓ ↓ |— it in the rung; the operator is true only when this difference occurs. Theoperator can be used to check for the rising or falling “edge” of the namedvariable(s), so that the associated action only occurs once. The indexvariable, if used in any of the preceding named variables, also appearsabove the differentiator symbol.Actions (Outputs)—( ) Relay On & Relay Off: The original ladder logic action was to energize thecoil of a relay – this remains the fundamental action. As long as the—( / ) associated test is true, then the coil (action) will be energized (true). Aextension of this concept is the NOT – as long as the test is true, the actionwill not be true. The named variable associated with the coil appears abovethese symbols as illustrated on the left.—( L) Latch & Unlatch: Situations exist wherein the test may be momentarily true,but the associated action should remain true until specifically made not true.—( U) Combinational logic can be used to create this action, or – more simply –the Latch and Unlatch actions may be used. If the test(s) in the rung used tolatch the coil is true then the named variable will be latched; a similar actionwill happen in the rung used to unlatch the coil. Rungs are tested andexecuted sequentially, as they appear in the task, so if both rungs aresimultaneously true then the action in the last rung to be executed willdetermine the state of the named variable. The symbols are shown on theleft.—( SCAN ) Scan: This action reads input data from physical I/O modules into the CPUmodule, and updates the appropriate variables in the several data tables. Theaction also writes data from the CPU data tables to the I/O modules. Andthe action updates mapped bit and value variables within the data tables.—( MOVE ) Move Low & Move High: When the associated test is true, these actionsmove (copy) value data from one variable to another without changing the—( MOVH) source variable. Move Low (MOVE) is more commonly used; it moves all16 bits of one value variable to another value variable. Move Low may alsobe used to move 8 consecutive bits in a single-column table into the lowbyte of a value variable (bit packing); Move High (MOVH) would be usedto move 8 other consecutive bits in a single-column table into the high byteof the value variable. MOVE or MOVH can also be used to move the low orhigh byte respectively of a value variable to 8 consecutive bits of a single-column table (bit unpacking).
The ToolBox for MOSCAD RTUs22The ToolsToolBox is a collection of software programs that eases the task of coding theflowchart steps and making the RTU run the application correctly. A printer isrequired if the user wants hard copies of the application; the application is also storedon the hard disk.After installing ToolBox, the icons of the various tools included in your packageappear in the MOSCAD Programming ToolBox folder, as shown below.Many of the basic tools are described in detail in the System Setup and Diagnostics(SSD) manual. These include, Site Configuration, Network Configuration, variousUtilities, and Diagnostic tools.To start a tool:1. Connect to the RTU (though you can set configuration values and developapplications without an RTU connection).2. Double-click the icon of the tool you want. If a password is required, thefollowing dialog box appears.3. Type the password and click OK.4. The main window of the selected tool appears. If a password was required, butwas incorrectly entered, no communication is established between the RTU andthe ToolBox. If the Cancel button is pressed, the tool starts up, but some of thecommunications-related functions will be hidden (gray)
The ToolBox for MOSCAD RTUs23Site Configuration (MOSCAD-L)Let’s start with Site Configuration (this brief tour illustrates the site configuration forMOSCAD-L; the processes described here are very similar to those that apply to thefull MOSCAD system). This program is used to define which I/O modules are presentin the unit and where they will be placed in the module rack. It is also used todetermine the functionality of the RS-232 and radio (modem) ports on the CPUmodule to be defined. The address of the specific RTU is then defined, and thecombination downloaded into the RTU’s CPU module. This process gives somepersonality to the RTU; this process must be accomplished via a local cable betweenthe ToolBox computer and the RTU.After activating the MOSCAD-L Site Configuration application, the followingwindow appears:The File menu includes commands for starting a new configuration, retrieving anexisting set (file) of configuration values, saving a configuration, printing the contentsof a configuration file, and the like. Click the File menu (or press ALT+F) to open it.It looks as shown below.
The ToolBox for MOSCAD RTUs24To start configuring a site, select the New command from the File menu or click on theNew icon. This automatically opens a new file, with default configuration settings, asshown below. The sections marked Module1 Module2, Module3 each represent anexpansion I/O module in the unit. (See the picture of the unit in The RTU sectionabove.) The CPU module does not appear on the Site Configuration screen, as it isalways placed in Rack 0, Module 0. The other I/O modules may be specified byclicking the desired Module (e.g. Module1) button.After clicking Module1, the I/O Modules dialog box appears, which enables you toselect a type for the module:After selecting the module type from the list, click OK.Repeat the process (click the Module2 button, then open the type list, etc.) for all therequired I/O modules. Made a mistake? Just click Type again, and select anothervalue from the type list. The current definitions of the three ports of the CPU moduleappear on the main window. One port, usually Port 1, is by default defined as LinkName = Computer 1, and Port Type = RS232- Local Computer. Use this port for thelocal connection of the ToolBox. To see the default port definition, click the Port 1button. The following is displayed:
The ToolBox for MOSCAD RTUs25The other two ports are configured in a similar way, though the values vary. Port 2defaults to the same configuration as Port 1, but can be changed as necessary. Port 3usually defines the communications medium required (e.g. radio, modem ). Once theports are configured, the values are saved in a site configuration file and downloadedto the unit. The Site Configuration section of the System Setup and Diagnosticsmanual describes the types and parameters for each port, as well as the procedure fordefining, saving and downloading the site configuration to the RTU.Network ConfigurationThe second major step is configuring the network. Most data radio communicationsystems have a single base transmitter located somewhere near the center of thephysical coverage area, as illustrated below. The transmitter emits radio energy; thedistance the emission travels define the coverage limits of the system. Normally, alldata equipment will lie within this coverage area, in which case, no networkconfiguration need be defined.RTURTURTURTURTUHowever, if one or more sites with data equipment lie outside this coverage area;reliable communications with these sites cannot be assured. The RTU provides asolution to this problem which requires no additional hardware. A map of the networkis created and existing units are used to relay information around the network to itsdestination.
The ToolBox for MOSCAD RTUs26Any RTU can receive data, validate that data, and store it in a buffer forretransmission a few seconds later. An RTU with more than one communicationsmedium (link), known as a “network node”, stores the data and relays it to anotherRTU. Note that network node RTUs are also capable of operating as regular RTUs;thus no special, dedicated hardware is required. The data Store & Forward capabilityis a communications protocol task; and requires nothing to be programmed in theapplication.A logical name is assigned to each communications medium in the network (e.g.Radio1, Radio2, Line1, Line2). Most sites will have a single communications medium– these are not network nodes. A few sites may have both a radio and a wirelinemodem, or two radios – these are definitely network nodes. Some sites may have asingle radio that communicates both with the main portion of the system and also withone or more out-of-range RTU sites. These are also network nodes; the link nameswould be Radio1/Zone1 and Radio1/Zone2 (abbreviated Radio1/1 and Radio1/2respectively) or their equivalent.Use the Network Configuration program to define these network nodes and theirrespective links, as described in the Network Configuration section of the SystemSetup and Diagnostics manual.Application ProgrammerOnce the site and network have been defined, building the application can be built,using the Application Programmer. The application (also called a project) consists ofa database and a ladder program.1 Activate Application Programmer from the MOSCAD Programming ToolBoxfolder, as you opened the Site Configuration and Network Configuration. (If youchose not to connect to the unit at this time, hit CANCEL when prompted for theCommunication driver password. The main window appears as shown below. Notethat most of the icons will be dimmed and unselectable.2. From the Project menu, select the New command, or click on the New icon. TheNew dialog box is displayed. The ToolBox lists all existing applications (projects)under Directories; hence the list may vary from computer to computer.
The ToolBox for MOSCAD RTUs273. For each project, Application Programmer opens a new subdirectory undertbox750\user. The path appears in the Selected Path box, and the insertion point ispositioned where you are expected to type the name of the project. Type a projectname of up to 8 characters and click the Create button. This creates the sub-directories and the application files. Anything you save related to the application willbe stored in that directory. Another user (e.g. user1) area can be created by changingthe value in Selected Path.4. Open the Edit menu. The commands Database Builder, Process Programming andI/O Link represent the main application building steps.Database BuilderDatabase Builder is used to create the application variables. Variables are “declared”in table-like windows.Select Database Builder from the Edit menu. The following dialog box is displayed.The Database Builder window tabs show three types of tables, User Tables (created bythe user specifically for the project), System Tables (available to the project), andConstants Table (available to the project). User Tables is selected by default. Hereyou may create (Append) and Edit tables of variables which represent the inputs andoutputs of your system, as mentioned in Database Principles above. For full details,see the Application Programmer manual.
The ToolBox for MOSCAD RTUs28Process ProgrammingThe defined variables may now be used in the coding of the various rungs of theapplication, which determine what actions are performed, under what conditions. Youmay wish to refer at this time to the lists of available tests and actions in ProgrammingPhilosophy above. Tests, actions, and variables – you're ready to go. Both the DataBase Builder and the Process Programming use an Append/Add capability to define anew table or process, and an Edit capability to insert variables or logic statements intothat table/process. Open the Edit menu and select Process Programming. Thefollowing dialog box is displayed.The MAIN process exists by default because it automatically runs at powerup or uponan application restart. The MAIN process provides the framework in which theapplication runs. Process and Rung Operations enable you to add and edit new rungsand processes. The logic of the rungs is programmed according to the logic of theflowchart created, which was based on the tasks required of the RTU. For full detailson Process Programming, see the Application Programmer manual.I/O LinkThe Site Configuration program is used to define the physical aspects of the RTUhardware. The Application Programmer program is used to define a virtual process
The ToolBox for MOSCAD RTUs29that has no link to any physical reality. Yet such a link is required. This is done usingI/O Link.1. In the Application Programmer main window, open the File menu and select ImportSite Configuration.2. Select the site configuration file related to your application (field.cfg).3. Open the Edit menu and select I/O Link. The following dialog box is displayed.4. The I/O Link dialog displays the application tables. The Status column shows thosetables that include an I/O module which requires linking. The minus sign indicatesincomplete link data. Highlight the first table that needs link information and click theEdit button. The table is displayed.For each variable in the table, enter the appropriate Rack and Module numbers on theRTU and the desired physical input or output on the specified module. Thesedefinitions are saved together with the rest of the project information. For a fulldescription of the I/O Link procedure, see the Application Programmer manual.The link process is the only association between the physical reality of the siteconfiguration and the virtual reality of the application. If the site configuration is
The ToolBox for MOSCAD RTUs30subsequently revised, the new version should be imported into the project. Theapplication itself is not necessarily affected.CompilerOnce the application is saved, it must be converted into a form which can beunderstood by the CPU. The compiler turns the visual ladder logic table and rungdefinitions into code to be executed directly by the microprocessor in the CPUmodule. Open the Run-Time menu in the main window and select the Compilercommand. A two-pass compilation takes place. Errors are reported along with theassociated rung name. You must correct these errors to produce error-free compiledcode. A successful compilation produces an “End of Compilation” message thatprovides a few items of information.Downloading and MonitoringThe compiled code is ready to be downloaded into the CPU module. This can be donelocally, using a cable, or remotely over the communications network (from any site inthe system to any other site in the system).The runtime operation of the downloaded code may be monitored via an upload fromthe CPU. You can upload locally using a cable, or via the communications network.You may monitor the runtime values in any table or in any rung – you choose thepresentation format.
32Remote Terminal UnitThe MOSCAD Remote Terminal Unit (RTU) is a modular unit, comprised of a CPUmodule, communication boards, and I/O modules interconnected by a common modularbus. The modular construction allows you to configure each RTU according to the preciserequirements of the application. It also permits future expansion as the applicationdevelops.The lighter model, MOSCAD-L RTU, includes only a CPU and three I/O modules.The RTU HardwareThe core of the RTU is the CPU module. The other modules provide digital (discrete) andanalog input/output capabilities.Each module is enclosed in a plastic box, which allows for fast assembly/disassembly(snap-in technique) without the need for tools.In the MOSCAD RTU, each module has LED indicators that monitor operations.CPU ModuleThe MOSCAD CPU module, based on the high-performance Motorola IntegratedMultiprotocol Processor (IMP) MC68302, provides three communication channels, one ofwhich is an interchangeable interface plug-in board. The module is located in slot 0 of racknumber 0 - the leftmost module on the first bus of the first rack.MOSCAD-L is based on the LC68302 processor and provides three communicationchannels.MemoriesThe CPU board contains two types of on-board memories:•Static CMOS RAM (SRAM), used for storing data and system parameters. The RAM isbacked-up by a lithium battery.•Segmented FLASH memory, used for storing the system program, the site configurationinformation, the user application, and the system configuration data, and programmedvia Programming Toolbox.Front Panel - MOSCADThe CPU module’s front panel includes the following:•Communication port connectors•Twenty diagnostic LEDs•Two push-buttons•BatteryCommunication Ports
Remote Terminal Unit33The CPU module has three communication ports with the following characteristics:•Communication port 1 with two interface options:RS-485 for UART start/stop operation and baud rate of up to 57,600 b/sec (port 1A).RS-232C with full DCE/DTE operation and baud rate of up to 57,600 b/sec (port 1B).•Communication port 2 with RS-232C interface as port 1b.•Communication port 3 – a plug-in port designed for various radio or linecommunications. The available plug-in boards are listed in Site Configuration.The two RS-232C ports (1b and 2) may be configured by the site configuration software(see Site Configuration in the System Setup and Diagnostics Tools manual). The defaultconfiguration of both ports is RS232 Local Computer.Diagnostic LEDsInMOSCAD,the20diagnosticLEDsarearrangedin4x5matrix.ThefunctionofeachLED is described below:PWR LOAD CONF APPLAC TX1 TX2CPU ERRMONRX2RST BAT CM1 CM2FAIL PORTSRX1CPUTX3RX3CM3PWR (Power): Lights as long as the 12 V DC input power is applied to the RTU,indicating that the unit is operating.AC (AC Fail): Lights when the AC power supply to the unit fails (operates on the unit’s 12V battery).CPU (CPU Fail): Lights to indicate a malfunction in the CPU. The nature of themalfunction is indicated by the 16 LEDs situated in the four columns on the right, whichlight simultaneously with the CPU Fail LED, as detailed below (CPU LED is on):•(1) CM3 LED is on: RAM test has failed.•(2) RX3 LED is on: ROM test has failed.•(3) CM3 and RX3 LEDs are on: FLASH memory test has failed.
Remote Terminal Unit34•(4) TX3 LED is on: Create software module has failed. (There is probably not enoughmemory. It is advisable to add a memory extension board or to reduce memoryconsumption.)•(5) CM3 and TX3 LEDs are on: Real time clock has failed.•(6) RX3 and TX3 LEDs are on: Internal clock has failed.•(7) CM3, RX3, and TX3 LEDs are on: Hardware breakpoint has failed.•(8) MON LED is on: XTAL rate change has failed.•(9) CM3 and MON LEDs are on: User request has failed.•(10) RX3 and MON LEDs are on: Application version was compiled and downloadedby a previous version of the Programming Toolbox.•(11) RX3, CM3, and MON LEDs are on: The current site configuration wasdownloaded by a previous version of the Programming Toolbox.RST (CPU Reset): Flashes upon reset of the CPU, usually caused by the watchdog timer,indicating that the software is not running properly.ERR (Error): Lights to indicate that an illegal state has been detected in the software, or amodule/board is missing, and other malfunctions. These events are logged in a specialerror logger in the CPU. The contents of the error logger may be read via ProgrammingToolbox (see Diagnostics in the System Setup and Diagnostics Tools manual).BAT (low battery voltage): Lights to indicate that the voltage of the lithium battery (whichbacks up the CMOS RAM when the 12 V voltage is not supplied to the modules), is low.The battery must be replaced. Note that the battery may be replaced without interruptingRTU operation, by pulling out the used battery and inserting a new one.LOAD: Lights to indicate that a configuration definition or an application is beingdownloaded to the FLASH memory.CONF (configuration): Is lit to indicate that a site configuration definition has been loadedinto the FLASH memory.APPL (application): Is lit to indicate that an application has been loaded into the FLASHmemory. The LED flashes in the following cases:•When the application program is in the “STOP SCAN” state for performing diagnosticsvia the monitoring program of the Application Programmer.•When the application run-time is too long (more than 1.2 seconds). This is caused by amistake in the Ladder Diagram program, such as an infinite loop.•When the application program is in the STOP state during hardware test performed bythe Programming Toolbox.MON (monitor): Lights when the monitoring program of Application Programmerperforms symbolic debugging of the Ladder Diagram function. This is achieved byinserting breakpoints to obtain “snapshots” of the data during the process.TX1: Lights when the RTU is transmitting data via port 1.RX1: Lights when the RTU is receiving data via port 1.
Remote Terminal Unit35CM1: Lights when the communications channel used by port 1 is busy.TX2, RX2, CM2: As above, for port 2.TX3, RX3, CM3: As above, for port 3.By default, LEDs are always displayed. Even the command "Disable leds display" in "LedsTest" in the "HW Test" in the ToolBox will not turn any LEDs off. However, it is possibleto set a time out for the LEDs. In the Site Configuration, use the "Advanced" menu, choose"General System Parameters" and then "Leds". The "Leds operating mode" has a defaultvalue of "Light always". This may be changed to "Light up to time out". The default timeout is 600 seconds, which is ten minutes.When the time out is reached, the LEDs turn off. This provides a small savings inelectricity. Pressing the push-button will re-light the LEDs in CPU mode. When working in"Light up to time out" mode, the command "Disable leds display" in "Leds Test" in the"HW Test" in the ToolBox will turn all the LEDs off. Then the command "Enable ledsdisplay" will relight the LEDs in CPU mode.Push-button PB1The main function of PB1 is to turn the LEDs on and off, as follows:•When the push-button is pressed once momentarily, the display is activated•When the push-button is quickly pressed twice, the display turns off. To conserveenergy, the display turns off after 10 minutes if it is not switched off manually.•When the push-button is pressed continuously, all the LEDs light simultaneously (forLED test). The LEDs extinguish when the switch is no longer pressed.In all modules there are several LEDs that do not turn off when all other LEDs do. TheseLEDs, such as the four leftmost LEDs of the CPU module, indicate malfunctions andimportant events.Push-button PB2For the use of the ladder application.A CPU restart is performed when the RTU is switched on, and PB1 and PB2 are pressedsimultaneously for about 10 seconds continuously. A CPU restart is also performed whenPB1 and PB2 are pressed simultaneously for about 30 seconds continuously while the RTUis operating. This erases the user flash memory (i.e. site configuration, applications, etc.)and restores the RTU to the default configuration. The buzzer sounds when the RTU isrestarted.BatteryThe lithium battery backs up the CMOS RAM and the real time clock when the 12Vvoltage is not supplied to the modules. Note that the battery may be replaced withoutinterrupting the RTU’s operation by pulling out the used battery and inserting a new one.The RTU is shipped from the factory with the battery disconnected by an insulating strip(to prolong battery life). Carefully pull out the strip before working with the RTU. If theRTU is to be stored for a long time, do not forget to place the insulating strip.Buzzer
Remote Terminal Unit36The buzzer sounds during the cold start-up of the CPU module and while erasing theconfiguration/application from the FLASH memory.Front Panel – MOSCAD-LThe CPU module’s front panel includes the following:•Twenty diagnostic LEDs•One push-buttonDiagnostic LEDsIn MOSCAD-L, the LEDs are arranged as shown below:CPU M1 M2 M3LOAD1CONF5Appl9MON13RST2TX16TX210 TX314ERR3RX17RX211 RX315BAT4CM18CM212 CM316The upper row of four LEDs (CPU, M1, M2, M3) is used to indicate what information isdisplayed in the remaining sixteen LEDs (CPU, or I/O Module 1, 2 or 3). Each press of thepush-buttonswitchesfromCPULEDdisplaytoM1toM2toM3,andthenbacktoCPU.In any display mode, when blinking, M1, M2, and M3 also indicate I/O Module Fail.There are two possible reasons for I/O Module Fail:(1) Missing I/O module(2) Incorrect I/O module (doesn't match configuration in Flash)CPU RESET (RST LED)In the CPU LED display, one LED is NOT always under software control. This is the RSTLED (second row, first column). When ONLY the CPU LED and the RST LED are on,then the CPU is in RESET state and these LEDs are hardware controlled.When ONLY the RST LED is on during startup (CPU LED OFF), the CPU is performingpower up tests.CPU LEDs on startup: SERIOUS FAILURE (CPU FAIL)When a SERIOUS FAILURE is found during startup power up tests, the ERR LED willblink (CPU LED OFF). For example, on ROM fail, or RAM fail, or CREATE fail, theERR LED will blink, and the LEDs in columns 3 and 4 will contain the error codeindicating the CPU error. (See list of errors under CPU Fail in MOSCAD DiagnosticLEDs above.)
Remote Terminal Unit37AI LEDsIf both the UDF and the OVF LED for a channel are on, this indicates that the specified AIchannel is not calibrated. If this occurs in the field, it indicates a hardware problem withthe IO module.DC On-Off SwitchIn MOSCAD-L versions up to and including V2.0x, switching DC OFF with the DC On-Off switch normally causes COLD RESTART. This is different than MOSCAD, whichhas a Lithium Battery backup to provide WARM RESTART.As of version V2.40, WARM RESTART may be triggered on MOSCAD-L (e.g. to replacea faulty I/O module,) if you have AC FAIL (see below) when you switch DC OFF. Firstdisconnect the PWR IN connector, and wait until the PWR LED goes off. This is ACFAIL. Then switch DC OFF. Replace the I/O module. When DC is switched ON again,you should get WARM RESTART, if the battery is connected and functioning. Don'tforget to reconnect the PWR IN connector; otherwise the battery will be drained. Thisprocedure enables WARM RESTART on systems with Solar Panel which never have ACFAIL.COLD RESTART is performed by switching DC OFF with the DC On-Off switch, whilepushing the push-button. ( ≥V2.40)LEDs TimeoutBy default, LEDs are always displayed. Even the command "Disable leds display" in "LedsTest" in the "HW Test" in the ToolBox will not turn any LEDs off. However, it is possibleto set a time out for the LEDs. In the Site Configuration, use the "Advanced" menu, choose"General System Parameters" and then "Leds". The "Leds operating mode" has a defaultvalue of "Light always". This may be changed to "Light up to time out". The default timeout is 600 seconds, which is ten minutes.When the time out is reached, the LEDs turn off. This provides a small savings inelectricity. Pressing the push-button will re-light the LEDs in CPU mode. When working in"Light up to time out" mode, the command "Disable leds display" in "Leds Test" in the"HW Test" in the ToolBox will turn all the LEDs off. Then the command "Enable ledsdisplay" will relight the LEDs in CPU mode.Push-button PB1Push-button during normal operationWhen the push-button is pressed once momentarily, the display is activated. Everyconsecutive short pressing of the push-button advances the display mode in those moduleswhere more than one display mode is available.One long press (several seconds): Test LEDS. This will light all LEDS regardless of thedisplay mode. When the push-button is released, the display will return to the CPU displaystate. However, after pressing for ten seconds the display will return to the CPU displaystate, even if the push-button is still pressed.One very long press (thirty/forty seconds): Erase Flash. During normal operation, press thepush-button and hold it down continuously (thirty/forty seconds) until the LEDs blink
Remote Terminal Unit38three times. Then the MOSCAD-L will erase the User Configuration, Application andeverything else in the Flash memory. After that, CPU RESET will occur.Push-button during startupPush-button pressed while power turned on: Download System. CPU LED begins to blink(all other LEDs off). CPU is in "Download System to Flash" mode.Push-button pressed after power is turned on and all LEDs are on: Erase User Flash.During startup, while all LEDs are on, press the push-button and hold it down continuouslyuntil the LEDs blink three times. Then the MOSCAD-L will erase the User Configuration,Application and everything else in the Flash memory. After that, CPU RESTART willoccur.The push-button is also used when downloading system software (see System Downloadersection in System Setup and Diagnostics Tools manual.)I/O ModulesThe RTU uses modular design with a variety of modules, such as:•Input modules, for discrete inputs and input counters or analog inputs•Output modules, for discrete outputs or analog outputs•Mixed input/output modulesRTU SoftwareThe RTU software design is based on an object-oriented Multi-Tasking Executive System(MTE). It has been designed so that during “cold start-up” it creates all software entitiesneeded to support the different hardware modules and communication ports as configuredvia Site Configuration program by the system engineer. This permits the use of only onestandard software package for all RTUs and provides flexibility in supporting theapplication requirements without sacrificing efficiency.The software supports a communication protocol based on the OSI model (published byISO). The protocol comprises all of the seven recommended layers, adapted for SCADA.The RTU software also provides the following:•Ladder application processes divided to run under up to five different priorities, toimprove time efficiency. Another ten tasks can be run by ‘C’ Toolkit.•Real time symbolic monitor debugger for the Ladder Diagram application.•Clean power-down/power-up recovery of the RTU (supported by software andhardware). After power-up, the RTU continues from the same task that was suspended.The RTU’s real time clock continues to advance with battery power during the outagetime. The application decides whether anything is to be done about “lost” time.•Clock synchronization – between various RTUs; can be activated via the ToolBox or aLadder application.•Background “housekeeping” of the software entities – to detect software and hardwaremalfunctions.
Remote Terminal Unit39•An error logger to store all abnormal conditions (software and hardware) for retrieval atany time by the Programming Toolbox Error Logger from any port in the system (notnecessarily on the same RTU).•Diagnostics of every software entity (using symbolic entity names) in the RTU,provided from any port in the system.The RTU does not have option jumpers or potentiometers. All options and adjustmentsare software controlled. This increases reliability while reducing the risk of forgettingadjustments.
40MDLC Communication ProtocolThe MDLC communication protocol is based on the OSI (Open Systems Interconnection)model published by ISO. The protocol comprises the seven recommended layers adaptedfor SCADA, in which every RTU is simultaneously a distributed control unit and acommunication node serving itself as well as other units.Information is transmitted in the form of variable-length digital words. Advanced securitytechniques are employed to provide protection against false messages.The protocol is efficient for transferring small quantities of information, such asmeasurements and discrete statuses, as well as for transferring large quantities ofinformation, such as downloading software applications, including data base, process, etc.SITE AAPPLICATIONPRESENTATIONSESSIONTRANSPORTNETWORKMULTI-LINKPHYSICALSITE CAPPLICATIONPRESENTATIONSESSIONTRANSPORTNETWORKMULTI-LINKPHYSICALMULTI-LINKPHYSICALMULTI-LINKPHYSICALNETWORKSITE BCRC CRC CRC CRCThe following subparagraphs describe the seven layers of the protocol, shown in the figureabove:•Physical layer.•Link layer.•Network layer.•Transportation layer.•Session layer.•Presentation layer.•Application layer.
MDLC Communication Protocol41Physical LayerThe physical layer comprises the various communication ports and their associatedsoftware.The software contains all the specific handling required by the communication ports andprovides an identical interface to the link layer. In this way, it is possible to define astandard entity for the link layer.The software is flexible and adapts itself to the number of ports and their various types asdefined by the user, but the possibility of defining a large number of ports of various typesdoes not impair software efficiency.The physical ports may also be configured to provide hard-copy printout to a printer.Link LayerThe function of the link layer is to ensure proper communication over a singlecommunication channel. The information is stored in variable-length frames where the linklayer protocol contains the following fields (for a DATA frame):•The address of the unit to which the DATA is transmitted.•The address of the transmitting unit.•The number of the frame.•CRC for error detection.Dual addressing is used to allow RTU-to-RTU transmission without central intervention,transmission to several centrals, or a hierarchical system where some of the RTUs serve assub-centrals for the lower hierarchies.During reception, the address is identified by hardware (and not by software) at thephysical level, in order not to spend software time on checking words that are not intendedfor that specific RTU. This preliminary screening enables reception of at least fourdifferent addresses per RTU: single address to access a specific RTU, broadcast address toaccess a group of RTUs, and two additional addresses enabling various communicationoperations.A link entity associated with a channel may receive several types of information:information that is intended for that specific RTU and information passing through it andis designated to other RTUs. The link entity transmits an acknowledgment (ACK) to eachRTU according to the DATA received from it. The ACK word is separated from theDATA word, since the RTU receiving the DATA is not necessarily the same RTU towhich the ACK is addressed.The ACK word enables the receiving site to identify the missing frames and retransmitonly those frames, thus saving air time by not repeating all the information transmitted.The CRC is 32 bits or 16 bits per CCITT definition.The frame synchronization (FLAG), at the beginning and at the end of each word, istransmitted in different ways for different physical ports.
MDLC Communication Protocol42Network LayerA system is defined as a network whenever it uses more than one communication medium,such as wireline and/or various radios, as well as Store & Forward repeaters, all on a singlefrequency. The communications in the network occur among nodes, which physically maybe RTUs, centrals, or repeaters.The network layer and its protocol are responsible for routing packets in the network viathe various nodes to enable communication between any two sites in the network.It is possible to access any application anywhere in the system from any port in the system,such as the RS-232 ports of the various RTUs, for purposes of definition, monitoring,modification, diagnostics, error logging, etc.Transportation LayerThe transportation layer ensures END-to-END completeness of the informationtransmission (between the RTU that has transmitted the message and the one that shouldreceive it). This layer transfers the DATA in an orderly fashion to the session layer aboveit. The protocol of this layer assigns sequential numbers to the packets (independent of thenumbers assigned by the link layer) and transmits an ACK word to indicate that the DATAis complete and all packets are transferred in the appropriate order to the layer above.The transport layer performs multiplexing, thus enabling several session entities (logicalchannels) to operate via one physical port or several physical ports. It is possible to defineany number of logical channels, regardless of the number of physical channels defined.Session LayerThe session layer enables the definition of any number of entities (instances), which arecapable of conducting a session with a parallel entity in another RTU, a central, or a sub-central. These entities and their protocol simultaneously conduct several sessions betweenany two sites, i.e., to simultaneously run several applications such as data transfer,diagnostics, monitoring, etc., without interference between the applications. The sessionhandling includes the following:•Start session.•Synchronization of message direction.•End session.•Abort session.•Re-synchronize session.The session layer also provides for transfer of short one-frame messages from one site tothe parallel application at another site without the need to start a session.
MDLC Communication Protocol43Presentation LayerThis layer handles the presentation of the DATA received from the various applicationswithin the various packets. It performs the following:•Checks that the information transferred to the application is complete.•Compresses the information.•Encrypts the information.•Checks authentication.Application LayerThis layer contains all the communication applications required for maintaining a SCADAsystem, as detailed below:a. Application enabling bi-directional data transfer upon request from the data bases ofthe sites.b. Software for downloading configuration to the sites:•I/O modules definition.•Communication ports definition.c. Software for downloading and monitoring application software (defined by the userin the ladder diagram language) to the sites, including:•Definition of the data structure.•Object code of processes.•Real-time symbolic monitoring of data base and processes.d. Application for transmitting events and short messages.e. Application for broadcasts.f. Application for remote diagnostics of the hardware and the software.g. Application for the retrieval of error messages stored in the error logs of the sites.h. Application for the calibration of A/D and D/A modules.i. Application for communication analysis and accumulation of statistics.j. General Downloader to download various blocks (e.g. site configuration, ladderapplications, network configuration, phone book, “C” blocks, third party drivers,x.25 conversion table, IP conversion table, etc.)

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