A26 5988 2_2841_2302_2311_2321_2303_Component_Descriptions_Oct65 2 2841 2302 2311 2321 2303 Component Descriptions Oct65

Systems

Reference Library

IBM

System/360

Component

Descriptions-

2841

Storage Control Unit

2302

Disk Storage, Models 3 and 4

2311

Disk Storage Drive

2321

Data Cell Drive, Model 1

2303

Drum Storage

This

publication

contains

reference

information

for

the

operation

and

programming

of

storage

devices

which

attach

to

the

IBM 2841

Storage

Control

Unit.

These

storage

devices

include

the

IBM 2311

Disk

Storage

Drive;

the

IBM

2302

Disk

Storage,

Models

3

and

4;

the

IBM 2321

Data

Cell

Drive,

Modell;

and

the

IBM 2303

Drum

Storage.

File

No.

S360-07

Form

A26-5988-2

This

is a

reprint

of

an

earlier

publication

(Form

A26-5988

-1).

The

following

Technical

Newsletter

is

incorporated

in

this

edition:

Form

No.

N26-0131

Pages

iii

and

blank,

1

and

2, 13

and

14,

41

and

42

Date

10/22/65

Copies

of

this

and

other

IBM

publications

can

be

obtained

through

IBM

Branch Offices.

Comments

concerning

the

contents

of

this

publication

may

be

addressed

to:

IBM,

Product

Publications

Department,

San

Jose,

Calif.

95114

ii

Page

IBM

2841

STORAGE

CONTROL

UNIT.

• • • • • • • • • • • • •

••

1

Introduction.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

IBM 2841 F1.Ulctions

•••••••••••••••••••••••••••

Data

Character

Format

•••

•••••

••••••••••••••••••

Data

Characters

•••••••••••••••••••••••••••••

Data

Checking

••••••••••••••••••••••••••••••

Data

Character

Transfer.

• • • • • • • • • • • • • • • • • • • • •

••

2

Track

Format.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

2

Index

Marker.

• • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

2

Gaps.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

2

Home

Address.

• • • • • • • • • • • • • • • • • • • • • • • • • • •

••

3

Track

Descriptor

Record

(RO) • • • • • • • • . • • • • • • • • •

••

3

Data

Records

(Rl

-

Rn)

• • • • • • • • • • • • • • • • • • • • •

••

5

INPUT/OUTPUT

OPERATIONS.

• • • • • • • • • • • • • • • • • •

••

7

Instruc

tions

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Start

I/O

••••••••••••.••••••••••••••••••••

Halt

I/O

••••••••••••••••••••••••••••••••••

Test

I/O

••••••••••••••••••••••••••••••••••

T

est

Channel

•••••••••••

• • • • • • • • • • • • • • • • • • •

ChaIUlel

Operation

••••••••••••••••••••••••••••

ChaIUlel

Status

Word

••••••••••••••••••••••••••

Channel

Address

Word

•••••••••••••••••••••••••

ChaIUlel

Command

Word

•••••••••••••••••••••••

Program

Status

Word

••••••••••••••••••••••••••

Channel

Program

Branching

•••••••••••••••••••••

7

8

10

11

12

Control

Commands.

• • • • • • • • • • • • • • • • • • • • • • • •

••

12

Sense

I/O

Commands

• • • • • • • • • • • • • • • • • • • • • • •

••

15

Search

Commands

• • • • • • • • • • • • • • • • • • • • • • • • •

••

18

Read

Commands

• • • • • • • • • • • • • • • • • • • • • • • • • •

••

22

Write

Commands.

• • • • • • • • • • • • • • • • • • • • • • • • •

••

22

End-of-File

••••••••••••••

• . • • • • • • • • • • • • •

••

27

Multiple

Track

Operation

• • • • • • • • • . • • • • • • • • • •

••

27

Two

-ChaIUlel

Switch

••••

• • • . • . • . • . • • • • • • • • •

.•

27

iii

CONTENTS

Page

Record

Overflow

• • • • • • • • • • • • • • • • • • • • • • • • • • •

••

28

IBM 2311

DISK

STORAGE.

• • • • • • • • • • • • • • • • • • • • • •

••

29

Introduction

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

29

Device

Description.

• • • • • • • • • • • • • • • • • • • • • • • • •

••

29

Data

Storage.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

31

Operator

Controls

and

Indicators

• • • • • • • • • • • • • • • • •

••

31

Operating

Procedures

••••••••••••••••••••••••••

32

IBM

2302

DISK

STORAGE,

MODELS 3

AND

4 • • • • • • • • • •

••

34

Introduction

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

34

Device

Description.

• • • • • • • • • • • • • • • • • • • • • • • • •

••

34

Data

Storage.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • •

••

36

Indicators

••••••••••••••••••••

IBM

2321

DATA

CELL DRIVE

••••••••

Introduction

••••••••••••••••••••••••••••••••

Device

Description

••••••••••••••••••••••••••••

Data

Storage

•••••••••••.••••••••••••••••••••

Operator

Controls

and

Indicators

•••••••••••••••••••

Operating

Procedures

•••••••••••••••••••••••••••

IBM 2303

DRUM

STORAGE

••••••••••••••••••••••••

Introduction

••••••••••••••••••••••••••••••••

Device

Description

••••••••••••••••••••••••••••

Data

Storage

•••••••••

0

••••••••••••••••••••••

APPENDIX

A.

2841/2311

PROGRAMMING

EXAMPLE

•••••••

APPENDIX

B.

HEXADECIMAL-DECIMAL

CONVERSION

APPENDIX

C.

COMMAND

SUMMARY

36

37

38

39

40

41

43

46

51

APPENDIX

D.

TRACK

ORIENTATION

•••••••••••.•.••

52

INTRODUCTION

The

IBM 2841

Storage

Control

Unit

provides

for

the

attachment

of

direct

access

storage

devices

to

IBM

System/360.

These

storage

devices

are:

IBM 2311

Disk

Storage

Drive

(standard

feature)

IBM 2302

Disk

Storage,

Models 3 and 4

(special

feature)

IBM 2321

Data

Cell

Drive

(special

feature)

IBM 2303

Drum

Storage

(special

feature)

A

single

2841

Storage

Control

Unit

provides

for

the

attachment

of

any

combination

of the above

stor-

age

devices

up

to

a

maximum

of

eight

access

mech-

anisms.

With

the

2841 Additional

Storage

special

feature,

up

to

eight

access

mechanisms

may

be

added,

bringing

the

total

available

access

mechanisms

to

sixteen.

A

versatile

set

of

instructions

ensures

optimum

data

processing

efficiency.

Direct

access

to

vast

quantities

of

operating

information

enables

the

user

to

locate

specific

data

records

without

sequential

ad-

dress

searching.

Voluminous

master

record

files

can

be

stored

on-line,

ready

for

immediate

reference

or

updating.

Maintenance

of

master

record

files

can

be

im-

mediate

and

direct;

the

most

current

information

can

be

entered

into

the

proper

area

of

the

master

record

file

as

transactions

occur.

Complex

account-

ing

procedures

can

be

Simplified,

because

interme-

diate

manual

operations,

necessary

to

maintain

off-

line

record

files,

are

eliminated.

IBM 2841

Functions

The

2841

performs

the

following functions:

•

Interprets

and

executes

commands

from

the

channel

attached

to

the

central

processing

unit

(CPU).

•

Provides

a

path

for

data

between

the

CPU

and

attached

storage

devices.

•

Translates

data

appropriately

as

it

is

trans-

ferred

between

the

storage

devices

and

the

CPU.

•

Furnishes

operation

status

information

to

the

CPU.

•

Performs

checks

to

ensure

accurate

transfer

of

data.

IBM 2841 STORAGE CONTROL UNIT

DATA CHARACTER FORMAT

Data

Characters

The

basic

unit of

data

within

all

components

of

the

IBM

System/360

is

called

a

byte.

A

byte

is

eight

bits

in

length.

A

single

byte

can

represent

one

alphameric

character,

one 8

-bit

binary

number,

or

two

decimal

digits.

The

eight

bits

of

each

byte

can

be

arranged

in any

of

256

combinations.

Decimal

Values

of

Byte Positions

,128

I

64

I

32

I

16

I 8 I 4 I 2

o 4

A Byte

Containing

the

Number

19

I

0 I 0 I 0 I I 0 I 0 I

0 1 2 3 4 5 6

~

A group

of

is

called

a

field.

A

series

of

is

called

a

record.

A

series

of

similar

records

is

known

as

a

logical

file.

The

length and

organization

of

records

and

logical

files

is

versatile

and

is

based

on

the

needs

of

the

data

processing

application.

First Record Second

Re

Field

Name: Social Security Name Address Social Security

Bytes

Required:

Number

5*

30 30

*Two Digits

per

Byte

Records and Fields within a

Fi

Ie

Data

Checking

CPU

(Central

Processing

Unit)

-

Parity

Number

5*

To

ensure

data

accuracy,

a

parity

bit

is

associated

with

each

byte

within

the

CPU.

When

the

byte

is

formed,

the

parity

bit

is

set

to

"zero"

or

"one"

to

maintain

an odd

number

of

"one"

bits

within

the

byte.

This

is

called

odd

parity.

N(

1

Whenever

data

is

accessed

by

the

CPU,

its

parity

is

checked.

Storage

Units

-

Cyclic

Check

In

2841

controlled

storage

devices,

data

is

stored

and

retrieved

in

Areas,

which

contain

one

or

more

fields.

Storage

capacity

can

be

more

efficiently

used

by

associating

check

bits

with

each

area,

rather

than

with

each

byte.

ov----"

Count Area Key Area

Dota

Area

Count

Areas Within Records

As

data

is

transferred

from

the

CPU

to

an

attached

storage

device,

the

2841

removes

the

parity

bit

from

each

byte.

The

2841

then

computes

two

Cyclic

Check

(cc)

bytes

which

are

added to

the

end

of

each

Data

Area.

The

two

Cyclic

Check

bytes

are

arithmetically

coded

to

represent

the

data

in

the

associated

area.

The

Cyclic

Check

code

detects

the

following

types

of

errors:

1. All

errors

occurring

within a

16-bit

span.

2. All

errors

involving

an

odd

number

of

bits

over

any

span.

3.

Errors

involving

an

even

number

of

bits

over

a

span

greater

than

16-bits,

except

in

certain

cases.

During

a

transfer

from

a

storage

device,

all

areas

read

are

inspected

by

the

2841.

Cyclic

Check

bytes

are

recalculated

for

each

area

and

compared

with

those

retrieved

from

storage.

An unequal

com-

parison

will

set

Data

Check

Error

indicators.

As

the

2841

transmits

data

to the

CPU,

Cyclic

Check

bytes

are

removed

and

parity

bits

are

restored

as

needed

to

maintain

odd

parity

.

Data

Character

Transfer

Information

is

transmitted

between

the

CPU

and

2841

Storage

Control

Unit one

byte

at

a

time.

A

ninth

bit,

the

odd

parity

or

check

bit,

is

added

as

needed

and

is

associated

with

each

byte.

Thus,

nine

bits

are

transferred

simultaneously

(in

parallel)

be-

tween

these

two

units.

This

transfer

method

is

called

parallel-by

-bit.

2

Information

is

transferred

between

attached

storage

devices

and

the

2841

one

bit

at

a

time

(in

serial).

This

transfer

method

is

called

serial-by-

bit.

---

The

2841

converts

data

from

serial-by-bit

to

parallel-by-bit

or

from

parallel-by-bit

to

serial-by-

bit

to

provide

data

movement

between

the

CPU

and

the

attached

storage

devices.

System

360

CPU

Parallel

By

Bit

TRACK FORMAT

o.

1~

2

3

4

5

6

7

C

2841

Storage

Control

Unit

Serial

By

Bit

76543210

Data

Transfer Format

Storage

Device

All

direct

access

st<.>rage

units

associated

with

the

2841

use

the

same

track

format:

Index

Home

Mar

ker Address

Record

R.0

Dato

Record

R 1

Dota

R

T

roc

k

Format

Index

Marker

The Index

Marker

indicates

the

physical

beginning

of

each

track.

There

is

one index

marker

per

record-

ing

medium

(disk

pack,

drum,

strip).

All

tracks

on

a

device

are

synchronized

by the

same

index

marker.

No index

indication

appears

on individual

records.

Gaps

(G)

Gaps

(G)

separate

record

areas

on

recording

tracks.

Gap

lengths

will

vary

depending on

storage

device,

location

within

the

record

and the

record

length.

Home

Address

The

Home

Address

consists

of

seven

bytes

which

define

track

condition and

physical

location

within

the

storage

device.

There

is

one Home

Address

per

track.

Home

Addresses

are

transferred

from

the

CPU

to the

storage

device

only by a

Write

Home

Address

operation,

and

from

the

storage

device

to

the

CPU

only

by

a

Read

Home

Address

operation.

Writing

Home

Addresses

is

usually

accomplished

by

utility

programs.

Index Home

Merker

Address

Home Address

Flag

A

flag

(1 byte)

indicates

track

condition.

It

is

nor-

mally

all

zero

bits

when Home

Addresses

are

first

written.

Bit

significance

is:

Bit FWlction

0 Zero

Zero

2 Zero

3 Zero

Flag

4 Zero

Byte

5 Zero

6

Track

Condition

o indicatE:s

operative

track

1

indicates

defective

track

7

Track

Use o

indicates

primaty

track

1

indicates

alternate

track

Cylinder

Number

The

cylinder

number

(2

bytes)

identifies

the

storage

unit

cylinder

within

which

the

data

is

stored.

Read/Write

Head

Number

The

read/write

head

number

(2

bytes)

identifies

a

read/write

head

w\thin

the

selected

cylinder.

The

combination

of

cylinder

and

read/write

head

numbers

is

used

to

locate

a

specific

track.

A

more

detailed

discussion

of

addressing

schemes

will

be

found

in

the

descriptions

of

the

various

storage

units.

Cyclic

Check

A

Cyclic

Check

is

used

for

error

detection

as

de-

scribed

in

the

section

on

Data

Checking. Two

bytes

are

required

for

this

check.

Gap

This

is

a fixed

gap

generated

by

the

2841

to

separate

the Home

Address

from

the

area.

Track

Descriptor

Record

(RO)

The

first

record

following

the

home

address

on

each

data

track

is

the

Track

Descriptor

Record

(Figure

1),

or

RO.

Although

it

may

be

used

to

store

data,

RO

has

been

designed

to

enable

entire

tracks

to

be

moved

to

alternate

tracks

if

a

portion

of

the

primary

track

becomes

defective.

For

description,

a

pri-

mary

track

is

considered

the

original

track

on

which

data

was

stored,

and

an

alternate

track

contains

data

which

has

been

repositioned

from

a

defective

primary

track.

This

repositioning

is

independent

of

the

file

organization

scheme

in

use.

Count

Area

This

I1-byte

area

describes

the

Data

Area

and Key

Area

which follow.

Flag.

Byte

0 of

the

Count

Area

is

generated

by

the

2841

as

RO

is

written.

It

is

not

sent

from

the

CPU.

Bit

Function

or

Setting

0 Zero

Zero

2 Zero

3 Zero

Flag

4 Zero

Byte

5 Zero

6

Track

Condition

o

indicates

operative

track

1

indicates

defective

track

7

Track

Use o

indicates

primary

track

1

indicates

alternate

track

3

Index

Marker

Home

Address Record

R~

Data Record R 1 Data R

__

--------~A---------~r----------------JA~--------------~----------~

Home

Address

I

CY~liC

Check

5 6

Figure

1.

Track

Descriptor Record

Count Area

Bits

6 and 7

are

transmitted

to

the

flag

bytes

of

all

records

on

the

track

from

the

flag

byte

of

the home

address

of

that

track.

Cylinder

Number.

In a

primary

track,

bytes

1

and 2 of

RO

contain

the

cylinder

number

of

the

primary

track

on which

this

record

was

stored.

If

this

record

has

been

moved

to

an

alternate

track,

the

cylinder

number

of

the

alternate

track

appears

in

the

data

area

of

RO

of

the

defective

primary

track.

Read/Write

Head

Number.

In a

primary

track

bytes

3 and 4 of

RO

contain

the

read/write

head

number

of

the

primary

track

on which

this

record

was

stored.

If

this

area

has

been

moved

to

an

alternate

track,

the

head

number

of the

alternate

track

appears

in

the

data

area

of

RO

of

the

defective

primary

track.

Record

Number.

Byte 5

designates

the

sequential

number

of

the

record

on

the

track.

For

RO,

the

record

number

is

zero.

Key Length. Byte 6

specifies

the

number

of

bytes

in

the Key

Area

of the

record

(excluding

check

bytes).

If

the

record

has

no key,

this

byte

is

zero.

This

byte

can

indicate

a Key Length

from

0

to

255

bytes.

Because

of

its

intended

special

use

with

alternate

track

procedures,

RO

will

normally

have no Key

Area.

Data

Length.

Bytes

7 and 8

specify

the

number

of

bytes

in

the

Data

Area

of

the

record

(excluding

check

4

Key Area Data Area

bytes).

Two

bytes

(16

bits)

can

indicate

Data

Length

from

1 to

65,535

bytes.

Zero

Data

Length

indicates

the

end

of

a

logical

file.

The 2841

sends

special

indicators

to

the

CPU

when

an

End-of-File

record

is

read

or

written.

Cyclic

Check.

Bytes

9 and

10

are

used

for

error

detection

as

discussed

in

the

section

on

Data

Check-

ing.

Key

Area

Although a Key

Area

can

be

written

and

used

in

RO

by

the

commands

used

by

the

2841,

this

use

is

purely

at

the

discretion

of

the

programmer.

Standard

use

of

RO

by IBM

Programming

Systems

does

not

include

a Key

Area.

A

more

detailed

discussion

of Key

Area

may

be

found

in

the

section

of

this

manual

which

describes

Key

Area

within

Data

Records

(R1

-Rn).

Data

Area

The

design

and

use

of

this

area

is

normally

pre-

scribed

by IBM

Programming

Systems.

Because

of

this

special

use

by

the

programming

system,

it

is

recommended

that

this

area

not

be

used

for

applica-

tion

data.

If

the

Data

Length

is

zero,

indicating End

-of-

File,

the

Data

Area

contains one byte

of

zeros

in

addition to the

check

bytes.

No

data

is

transferred

to

the

channel when

this

record

is

read,

but

the

End-

of -

File

indicator

is

set.

Data

Records

(R

1 -Rn)

One

or

more

data

records

may

follow

RO

on a

track.

Count

areas

make

each

record

self-formatting

for

maximum

data

organization

flexibility and

efficiency.

Index

HA

Dcrlal

~

Address

Marker

Address

Marker

* May

Not

be Present

Record R 1 -

Rn

Format

D

Address

Marker

This

2-byte

area

indicates

the

beginning

of

each

record

after

RO

(Figure

2).

Address

markers

are

supplied by

the

2841

as

records

are

written.

They

are

used

by the 2841

to

locate

the beginning of a

record

for

searching,

writing,

and

reading

operations.

Record R 1

Count

Area

This

II-byte

area

describes

the

Key and

Data

Areas

which follow

it.

Bytes

1

through

8

are

created

in

the

CPU by the

program

used

to

write

the

record.

Flag.

Byte 0

of

the

Count

Area

is

generated

by

the

2841

as

each

record

is

written.

It

is

not

sent

from

the CPU.

Flag

Byte

Bit

Function

o o for

even-count

records (RO,

~,

R4, R6)

1 for

odd-count

records

(R

1, R3,

Rs

• •

••

)

Used

by

the

2841

to

ensure

that

all

address

markers

(and

records)

are

present.

The

2841

signals a missing Address

Marker

when

two

consecutive,

identical

bits

are

encountered

(unless

an

Index

Point

intervenes).

Used

with

Record

Overflow

feature.

o for

all

non-overflow

records

and

for

the

last

record

of

an

overflow

chain.

for

each

record

except

the

last

record

of

an

overflow.

r'--------------------------~A~----------------------------~

Data Area

Data Area Address Mar ker

Figure

2.

Address

Marker

and

Count

Area

......

_K_e_Y_~J

J

Area

T

Count

Area

Address Marker

and

Count

Area

~_D_a_ta

_

_JI

~!

__

A_r_ea_~

G

Key

Area

5

~

2

3

4

5

Flag

6

Byte

7

Function

Zero

Track

Condition

0

indicates

operative

track

1

indicates

defective

track

Track

Use

o

indicates

primary

track

1

indicates

alternate

track

Bits 6

and

7

are

transmitted

to

the

flag

bytes

of

all

records

on

the

track

from

the

flag

byte

of

the

Home

Address

of

that

track

by

the

2841.

Cy

linder

Number.

Bytes

1

and

2

contain

the

cylinder

number

of

the

track

on

which

the

data

is

stored.

Read/Write

Head

Number.

Bytes

3 and 4

contain

the

read/write

head

number

of

the

track

on

which

the

data

is

stored.

Record

Number.

Byte

5

designates

the

sequential

number

of

the

record

on

the

track.

Key Length. Byte 6

specifies

the

number

of

bytes

in

the

Key

Area

of

the

record

(excluding

check

bytes).

If

the

record

has

no

key,

this

byte

is

zero.

This

byte

can

indicate

a Key Length

from

zero

to 255

bytes.

Data

Length.

Bytes

7

and

8

specify

the

number

of

bytes

in

the

Data

Area

of

the

record

(excluding

check

bytes).

Two

bytes

(16

bits)

can

indicate

Data

Length

from

1

to

65,535

bytes.

It

should

be

noted

that

maximum

data

length

is

a function

of

the

track

capacity

of

the

specific

storage

device.

See

the

description

of

the

Overflow

Feature

for

records

that

exceed

the

track

size.

6

Zero

Data

Length

indicates

the

end

of

a

logical

file.

Special

indicators

are

sent

to

the

CPU

when

an

End-of-File

record

is

read

or

written.

Cyclic

Check.

Bytes

9 and 10

are

used

for

error

detection

as

discussed

in

the

section

on

Check

Characters.

Key

Area

The Key

Area

concept

has

been

provided

in

storage

units

of the 2841

family

to allow

searching

and

data

accessing

during

a

single

disk,

drum,

or

strip

revolution.

The

Key

Area

can

contain

identifying

information

about

a

record,

such

as

serial

number,

social

security

number,

or

policy

number.

Special

commands

are

provided

to

search

Key

Areas

for

this

identifying

information.

When

the

desired

record

is

found, a

read

or

write

instruction

can

be

issued

and

the

Data

Area

read

or

written

during

the

same

revolution.

Comparison

(during

searching)

is

accomplished

within the 2841.

Thus,

use

of Key

Areas

for

search-

ing

allows

searching

and

comparing

of

keys

and

movement

of

the

desired

Data

Area

to

or

from

the

CPU

during

a

single

disk,

drum,

or

strip

revolu-

tion.

Key

Area

length

ranges

from

1

to

255

bytes.

Two

Cyclic

Check

bytes

are

added

to

the

Key

Area

by

the

2841.

If

Key Length,

in

the

Count

Area,

is

zero,

no Key

Area

will

be

written.

Data

Area

This

area

contains

the

information

identified

by

the

Count and Key

Areas.

Data

information

is

organ-

ized

and

arranged

by

the

programmer.

Two

Cyclic

Check

bytes

are

added

to

the

Data

Area

by

the

2841.

If

Data

Length

was

zero,

indica-

ting

End-of-File,

the

Data

Area

will

contain

one

byte

of

zeros

in

addition to

the

check

bytes,

however

no

data

is

transferred

to

the

channel

when

this

record

is

read.

Input/Output

(I/O)

operations

involve

the

transfer

of

information

to

or

from

CPU

storage.

Within

this

concept,

disk

and

drum

storage

drives

and

data

cell

drives

are

considered

I/O

devices.

The

CPU

program

initiates

I/O

operations

with

the

Start

I/O

instruction.

Bit

positions

24-31

of

this

instruction

identify

the

device.

Start

I/O

causes

the

channel

to

fetch

the

Channel

Address

Word

(CAW)

from

main

storage

location

72.

The

command

ad-

dress

portion

of

the

CAW

designates

the

location

in

main

storage

from

which

the

channel

subsequently

fetches

the

first

Channel

Command

Word

(CCW).

The

CCW

specifies

the

command

to

be

executed

and

the

storage

area

to

be

used.

If

the

channel

is

not

busy,

the

channel

attempts

to

select

the

device

by

sending

the

address

of

the

device

to

all

attached

control

units.

The

control

unit

specified

in

the

address

responds

to

its

selection

and

awaits

further

instructions.

The

command

code

is

sent

to

the

selected

control

unit;

the

control

unit

then

responds

with a

device

status

byte

to

the

CSW.

At

this

time,

the

start

r/o

is

terminated.

The

results

of

the

attempt

to

initiate

the

execution

of

the

command

are

indicated

by

the

condition

code

in

the

Program

Status

Word,

and,

under

certain

conditions,

by

status

bytes

in

the

Channel

Status

Word.

All

data

transfers

from

the

channel

to

the

2841

are

checked

for

parity.

If

a

parity

error

is

detected,

a

unit

check

signal

is

sent

to

the

CSW

by

the

2841

and

the

command

will

not

be

executed.

An

I/O

operation

may

involve

transfer

of

data

to

one

storage

area,

designated

by

a

single

CCW. When

data

chaining

is

specified,

data

is

transferred

to a

number

of

storage

areas.

In

each

case,

a

chain

of

CCWs

is

used,

in

which

each

CCW

designates

an

area

in

main

storage

for

a

part

of

the

operation.

The

program

can

be

notified

of

the

progress

of

chaining

by

specifying

that

the

channel

modify

the

Channel

Status

byte

upon

fetching

a new CCW. When

command

chaining

is

specified,

a

series

of

commands

is

executed.

Termination

of

an

I/O

device

operation

normally

is

indicated

by

two

CSW

conditions:

Channel

End

and

Device

End.

The

channel

end

condition

indicates

that

the

I/O

device

has

received

or

provided

all

informa-

tion

associated

with

the

operation

and no

longer

needs

channel

facilities.

The

device

end

signal

indicates

that

the

I/O

device

has

terminated

execution

of

the

operation.

The

device

end

condition

can

occur

con-

currently

with

the

channel

end

condition

or

later.

If

INPUT/OUTPUT

OPERATIONS

command

chaining

has

been

specified,

the

is

fetched

by

the

channel

and

the

operation

designated

is

commenced.

Unusual

conditions

and

errors

ter-

minate

the

execution

of

a

command

chain.

INSTRUCTIONS

All

I/O

instructions

use

the

following

format:

o

78

1516

1920

31

I/O

Instruction Format

Fields

in

the

instruction

are

allocated

as

follows:

Bit

Position

Field

Designation

0-7

Operation

(Op)

Code

8-15

Not

Used

16-19

20-31

Base Address

Register

Location

(B

1)

Displacement

(D 1 )

Function

Designates

the

operation

to

be

performed.

Designates

the

address

of

a

general

register

in

main

storage.

The

register

is 32

bits

in

length,

but

only

the

low

order

24

bits

are

used.

The

sum

obtained

by

the

addition

of

the

content

of

the

register

at

B1

and

content

of

the

D1

field

identifies

the

channel

and

device

addressed

by

the

instruction.

The

re-

sult

has

the

format:

2021

2324

31

7

Bit Position

Field

DesilEation

Function

0-7

Operation

(Op) Designates

the

operation

to

Code

be

perfonned.

8-20

Not

Used

21-23

Channel

Address

000

-deSignates

multiplexer

channel.

001 -110 -designates

selec-

tor

channel

1-6.

111 -

invalid

combination.

24

Shared

Channel

1

indicates

multiplex

channel

Indicator

or

sub-channel.

On

a

selec-

tor

channel,

this

bit

is

in-

cluded

in

the

control

unit

address.

25-27

Control

Unit

0-7

control

units

per

channel.

28-31

Access

Mechanism

0-7.

Bit

28

will

be

1

only

if

additional

access

feature

is

installed

(indicates

mecha-

nism

8-15).

Bit

positions

24 to 31

of

the

I/O

instruction

specify

a

control

unit

and

access

mechanism.

? I

C~ntrol

~nit

N~.

24

t 2S 26

27

Always 1 for 2841

on

Multiplex

Channel

28 t 29

30

31

Indicates

Numbers

8-15

When Add'i Access

Feature

Installed

Unit

Address Format

A

control

unit

number

is

permanently

assigned

to

each

2841

through

internal

wiring

at

the

time

the

unit

is

installed.

A

maximum

of 16

access

mechanisms

can

be

addressed

by

each

control

unit. A

standard

2841

can

control

eight

mechanisms;

eight

more

can

be

attached

with

the

Additional

Storage

feature~

Start

I/O

All

I/O

operations

are

initiated

by

a

Start

I/O

instruc-

tion.

If

the

channel

facilities

are

free,

Start

I/O

is

accepted

and the CPU continues

its

program.

The

channel

independently

selects

the I/o

device

specified

by

the

instruction.

The

CAW

at

main

storage

location

72

contains

the

protection

key

for

the

sub-channel

and

the

address

of

the

first

CCW. The CCW

so

designated

specifies

the

operation

to

be

performed,

the

main-storage

8

area

to

be

used,

and the

action

to

be

taken

when

the

operation

is

completed.

If

any of the

several

conditions

exist,

Start

I/O

will

cause

the

status

portion,

bit

positions

32-47,

of

the

CSW

at

main

storage

location

64 to

be

replaced

by a new

set

of

status

bits.

The

status

bits

pertain

to the device

addressed

by

the

instruction.

The

con-

tents

of the

other

fields

of

the

CSW

are

not

changed.

Halt

I/O

Halt

I/O

terminates

a channel

operation,

and

the

2841

is

disconnected

from

the

channel.

Halt

I/O

does not

cause

a command

byte

to

be

transferred

to

the

2841.

If the

operation

in

progress

was a

write

command,

the

2841

completes

the

write

operation

by

inserting

valid

zeros

to

the end of

the

field

or

track.

An

erase

command

also

inserts

valid

zeros

to

complete

the

operation.

Test

I/O

Test

I/O

sets

the

condition code in

the

Program

Status Word to

indicate

the

state

of

the

addressed

channel,

sub-channel,

and

I/O

device.

The

Channel

Status Word

is

stored

in

location

64.

Test

Channel

Test

Channel

sets

the

condition code in

the

Program

Status Word to

indicate

the

state

of

the

channel

ad-

dressed

by

the

instruction.

The condition code

then

indicates

channel

available,

interruption

condition

in channel, channel working,

or

channel not

opera-

tional.

The execution of

this

command

does

not

affect the

2841.

CHANNEL OPERATION

The IBM 2841

Storage

Control

is

attached

to the CPU

through

a

set

of

data

paths

called

a channel

(Figure

3).

So

that

the

CPU may

control

a wide

variety

of

input/output

devices

with a

minimum

of

programming

differences,

all

control

units

are

designed

to

re-

spond to a

standard

set

of

commands

from

the

chan-

nel.

The

control

unit

then

translates

these

com-

mands

into

specific

operating

orders

for

the

particu-

1ar

input/output

unit.

This

enables

the

CPU to

oper-

ate

all

input/output

devices

uniformly

with

the

set

of

basic

instructions.

Channel Status Word

(CSW)

The Channel Status Word

informs

the

program

of

the

status

of an

I/O

device

or

the conditions

under

which an

I/O

operation

has

been

terminated.

The

System/360

CPU

Issues

I/o

Instructions

Executes Commands (CCW's)

I

NSTRUCTIO

NS

and

COMMANDS

Figure

3.

Instructions,

Commands

and

Orders

Data

Cell

Drive

CSW

is

formed,

or

parts

of

it

are

replaced,

during

I/O

interruptions

and

during

execution

of

I/O

in-

structions.

The

CSW

is

placed

in

main

storage

at

location

64.

It

is

available

to

the

program

at

this

location

until the

interruption

occurs

or

un-

til

another

I/O

instruction

generates

a new CSW,

whichever

occurs

first.

When the

CSW

is

stored

as

a

result

of

an

I/O

interruption,

the

I/O

device

is

identified

by

the

I/O

address

in

the

old

PSW. The

information

placed

in

the

CSW

by

an

I/O

instruction

pertains

to

the

device

addressed

by

the

instruction.

2841

Storage

Control

The

CSW

has

the

following

format:

I Key I 0000 I Command Address

0 3 4

78

I

Device

St1tus

Channel

I

Count

32

39

40

4748

I

31

I

63

Channel

Status Word

~

F.ields in the

CSW

are

allocated

for

the

following

purposes:

9

CSW

Bit

Position

Field

Designation

0-3

Protection

Key

4-7

Not

Used

Function

Form

the

storage

protection

key

used

in

the

chain

of

operation.

Always zero.

8-31

Command

Address

Form

an

address

eight

positions

32

Attention

33

Status

Modifier

34

Control

Unit

End

35

Busy

36

Channel

End

37

Device

End

38

Unit

Check

39

Unit

Exception

10

higher

than

the

address

of

the

last

CCW

used.

Not

Used.

Set

whenever

a

Search

High,

Search

Equal,

or

a

Search

High

or

Equal

command

has

been

executed

and

the

con-

dition

satisfied.

The

Status

Modifier

is

also

set

whenever

the

2841 is Busy.

This

bit,

in

conjunction

with

the

Busy Bit,

signifies

Control

Unit

Busy.

Set

if

a

Control

Unit

Busy

status

has

been

generated

previously

and

the

busy

condition

has

been

terminated.

Indicates

that

the

selected

device

is

busy.

It

is

set

when

a

new

command

chain

is

initiated

while

the

selected

access

mechanism

is

still

in

motion

due

to

a

command.

In

conjunction

with

the

Status

Modifier

bit,

indicates

the

con-

trol

unit

is

busy.

It

is

set

when

a

new

command

chain

is

initi-

ated

while

the

2841 is

causing

a

track

to

be

erased

following

a

Format

Write

command.

See

section

on

Two

Channel

Switch.

Set

at

the

end

of

each

channel

command.

Indicates

that

an

access

mechanism

is

free

to

be

used.

Set

whenever

an

unusual

or

error

condition

is

detected

in

the

2841

or

the

selected

file

device.

A

Sense

1/0

Command

may

then

be

used

to

identify

the

condition.

Indicates

an

End-of-File

has

been

detected

during

a

Read

RO

CKD,

Read

KD,

Read

D,

Write

KD,

or

Write

D

operation.

It

results

from

a

Data

Length

of

zero

being

detec-

ted

in

the

Count

Area

of

a

record.

CSW

Bit

Position

Field

Designation

40-47

Channel

Status

48-63

Gount

Function

When

this

condition

is

detected,

no

data

is

transferred.

If

Key

Length

is

not

zero,

the

Key

Area

is

transferred.

Indicate

channel

conditions

as

follows:

Bit

Designation

40

Program-controlled

interruption

41 IncOlTect

length

42

Program

check

43

Protection

check

44

Channel

data

check

45

Channel

control

check

46

Interface

control

check

47

Chaining

check

Form

the

count

of

the

last

CCW

used.

Channel

Address

Word

(CAW)

Successful

execution

of

start

I/O

causes

the

channel

to

fetch

a

channel

address

word

from

main

storage

location

72.

The

CAW

specifies

the

location

in

main

s.torage

where

the

channel

program

begins.

The

CAW

has

the

following

format:

Command Address

o

34

78

31

Channel

Address

Word

CAW

fields

are

allocated

for

the

following

purposes:

CAW Bit

Position·

Field

Designation

0-3

Protection

Key

4-7

Function

Forms

the

Storage

Protection

key

for

all

commands

associated

with

Start

1/0.

This

key

is

matched

with

a

storage

key

whenever

data

is

placed

in

storage.

Always

Zero.

8-31

Command

Address

Designates

the

lacation

of

tIie

first

CCW

in

main

storage.

Channel

Command

Word

(CCW)

The

byte

location

specified

by

the

CAW

is

the

first

of

eight

bytes

of

information

(a

double word)

that

the

channel

fetches

from

main

storage.

These

64

bits

of

information

are

called

a Channel

Command

Word

(CCW). The

address

of

the

leftmost

position

of

the

CCW

must

be

divisible

by

four

(in

binary

notation,

the two

low-order

positions

of

the

address

are

zero).

One

or

more

CCWs

make

up

the

channel

program

that

directs

channel

operations.

The CCW

specifies

the

command

to

be

executed.

For

commands

initiating

I/O

operations,

it

desig-

nates

the

storage

area

associated

with

the

operation

and

the

action

to

be

taken

when

transfer

to

or

from

the

area

is

completed.

CCWs

can

be

located

any-

where

in

main

storage

and

more

than

one

can

be

associated

with a

Start

I/O.

The channel

refers

to

a

CCW

in

main

storage

only

once.

Once obtained,

the

pertinent

information

is

retained

in

the

channel.

The

first

CCW

is

fetched

during

the execution

of

Start

I/O.

Each

additional CCW in the

sequence

is

obtained when

the

operation

has

progressed

to a

point

where

the additional CCW

is

needed.

Fetching

of

CCW

s by the channel

does

not

affect

the contents

of

main

storage.

Fields

in

the

CCW

are

allocated

for

the following

purposes:

CCW Bit

Position

Field

Designation

0-7

Command

Code

8-31

Data

Address

32

33

34

Chain

Data

(CD)

Flag

Chain

Command

(cq

Flag

Suppress

Incorrect

Length

Indicator

(SIU)

Function

Specify

the

operation

to

be

per-

formed.

The

4

high-order

bits

specify

the

function

to

be

per-

formed

by

the

addressed

I/O

device;

the

2

low-order

bits

specify

the

channel

function.

Specify

the

location

of

an

8-bit

byte

in

main

storage.

This is

the

first

location

of

the

area

designated

by

the

CCW.

When

set

to

one,

specifies

chain-

ing

of

data.

It

causes

the

storage

area

designated

by

the

to

be

used

with

the

current

oper-

ation.

The

command

code

of

the

will

be

ignored.

When

bit

32 is zero,

the

current

CCW is

the

last

one

for

the

operation.

When

set

to

one,

and

when

the

CD

flag

is

zero,

specifies

chain-

ing

of

commands.

It

causes

the

operation

specified

by

the

com-

mand

code

in

the

to

be

initiated

on

normal

comple-

tion

of

the

current

operation.

Controls

whether

an

incorrect

length

condition

is

to

be

indi-

cated

to

the

program.

When

this

bit

is

set

to

one

and

the

CCW Bit

Position

Field

Designation

35

Skip

(SKIP)

Flag

36

37-39

40-47

Program-Control-

Interruption

(PC!)

Flag

Transfer-in-

Channel

48-63

Count

Function

CD

flag

is zero

in

the

last

CCW

used,

the

incorrect

length

indication

is suppressed.

When

both

the

CC

and

the

SILl flags

are

set

to

one,

command

chaining

takes

place

regardless

of

the

presence

of

an

incorrect

length

indication.

Absence

of

the

SIll

flag

or

the

presence

of

the

CD

flag

causes

the

pro-

gram

to

be

notified

of

the

in-

correct

length

condition

when

it

occurs.

When

set

to

one,

specifies

sup-

pression

of

a

transfer

of

infor-

mation

to

storage

during

a

read,

read-backward,

or

sense

op-

eration.

When

bit

35 is

zero,

normal

transfer

of

data

takes

place.

When

set

to

one,

causes

the

chan-

nel

to

generate

an

interruption

condition

upon

fetching

the

CCW.

When

bit

36

is

zero,

normal

operation

takes

place.

Bit positions

37-39

of

every

CCW

other

than

one

specifying

transfer

in

channel

must

contain

zeros.

Violation

of

this

restriction

gen-

erates

the

program-check

condi-

tion.

For

additional

information,

see

Control

Commands

-

Transfer-in-Channel.

Not

used.

Specify;

the

llumber

of

8-bit

byte

locations

in

the

storage

area

designated

by

the

CCW.

Program

Status Word (PSW)

A double

word,

the

program

status

word

(PSW)

con-

tains

information

required

for

proper

program

exe-

cution.

In

general,

the

PSW

is

used

to

control

in-

struction

sequencing and to hold and

indicate

the

status

of

the

system

in

relation

to

the

program

being

executed.

The

active

or

controlling

PSW

is

called

the

"current

PSW."

By

storing

the

current

PSW

during

an

interruption,

the

status

of the CPU

can

be

preserved

for

subsequent

inspection.

By loading a

new PSW

or

part

of

a PSW, the

state

of

the

CPU

can

be

initialized

or

changed.

11

The

PSW

has

the

following

format:

Program Status Word

ISystem Mask I

Key

I AMWP\

o 7 8

1112

15

16

32.

3334

35 36

3940

PSW

Bit

Position

Field

Designation

0-7

System

Mask

8-11

Interrupt

Key*

12 ASCII (A)*

13

Machine-Check

Mask (M)*

14

Wait

State

(W)*

15

Problem

State

(P)*

16-31

Interruption

Code*

32-33

Instruction

Length

Code (ILC)*

Interruption Code

31

Instruction Address

63

Function

Associated

with

I/O

channels

and

external

signals. When a

mask

bit

is

one,

the

source

can

inter-

rupt

the

CPU. When a

mask

bit

is zero,

the

corresponding source

cannot

interrupt

the

CPU

and

interruptions

remain

pending.

Identifies

the

cause

of

an

I/O,

program,

supervisor

call,

or

external

interruption.

34-35

Condition

Code (CC)*

36-39

Program

Mask*

40-63

Instruction

Address

*Refer

to

IBM

System/360

Principles

of

Operation,

Form

A22-6821.

Channel

Program

Branching

Normally

the

in

a chain

is

fetched

from

a

core

position

eight

bytes

higher

than

the

current

CCW.

This

sequence

can

be

modified in two ways:

12

1.

If

command

chaining

is

specified

in

the

cur-

rent

CCW

and execution of the

CCW

results

in

a

status

modifier

indication (without

other

unusual

conditions

detected),

the channel

will

fetch

the

from

a

main

storage

location

sixteen

positions

higher

than

the

current

CCW

(one

CCW

is

skipped). Since

all

Search

commands

transmit.a

status

modifier

indication,

this

allows

branching

from

a command

chain

when

the

search

command condition

has

been

satisfied.

2. The

programmer

can

also

modify the

CCW

chain

sequence

by

using

the

Transfer-in-

Channel (TIC)

command.

This

command

directs

the

channel to

fetch

the

from

an

address

specified

within

the

TIC

CCW. See

Control

Commands

-

Transfer-

In -Channel

for

additional

information.

These

methods

of

modifying

the

sequence

of a

chain

of

CCWs

provide

branching

capability

in

the

channel

program.

Control

Commands

Control

operations

on 110

devices

do

not

involve a

transfer

of

data

between a

storage

unit

and

the

CPU.

However,

in

certain

Control

operations,

a few

bytes

or

bits

may

be

transferred

between

the CPU and

2841 to

enable

the

operation

to

take

place.

These

bytes

are

parity

checked

during

transfer.

Erase

This

command

is

used

to

erase

the

end

of a

track

after

a

track

overflow

has

occurred.

It

has

the

same

chaining

requirements

as

a

Write

Count-Key-

Data

command.

The

execution

of

this

command

causes

one's

to

be

written

from

the

end

of the

Data

area

of

the

record

on which the

preceding

search

was

satisfied,

or

the

record

just

written

by

Write

CKD, to the

end

of

the

track.

Channel End and

Device End

signals

are

generated

when Index

Point

is

reached.

Both the channel and the

control

unit

are

busy

during

execution

of

this

command.

Erase Command Code

Decimal Hexadecimal Binary

17

11

0001

No

Operation

(No-Op)

This

command

causes

the

addressed

device

to

re-

spond

with

Channel End and

Device

End.

No

infor-

mation

other

than the

command

itself

is

trans-

ferred

to

the

2841. The

addressed

device

takes

no

action.

Channel

End

and Device

End

are

signalled

simultaneously

to

the

CSW.

No-Operation

Command Code

Decimal Hexadecimal Binary

03 03

00000011

Restore

This

command

is

used

with

the

2321 only,

It

causes

the

2321

to

restore

the

strip

from

the

drum

to

the

cell.

It

causes

Channel End

to

be

generated

upon

initiation

of

the

operation

by

the

Control

Unit and

Device End when

the

strip

is

fully

restored.

The

Restore

command

operates

exactly

like

a

seek

com-

mand

except

that

no

address

is

transferred

to

the

2841.

A

Restore

command

is

not

restricted

by

the

file

protect

mask.

Any

device

other

than

a 2321

performs

a No-op when a

Restore

command

is

given.

Restore Command Code

Decimal Hexadecimal Binary

23

17

00010111

Recalibrate

This

command

is

used

with

the

2311 only.

It

causes

the

2311 to

seek

to

head

zero

and

track

zero.

It

causes

Channel End

to

be

generated

immediately

and Device End to

be

generated

when

the

operation

is

complete.

Any

device

other

than

a 2311

performs

a No-op when a

Recalibrate

command

is

given. A

Recalibrate

command

works

under

the

same

File

Protect

Mask

as

a

Cylinder

Seek

command.

Reca

librate· Command Code

Decimal H exadec i

ma

I Binary

19

13

0001 0011

Seek

Three

seek

commands

are

associated

with

the

2841

Storage

Control

unit:

Seek,

Seek

Cylinder,

and Seek

Head.

After

a

Start

I/O

instruction

has

selected

the

proper

channel,

control

unit,

storage

unit, and

access

mechanism,

the

Seek

CCW

transfers

a

6-byte

Seek

Address

from

main

storage

to

the

2841.

The

CCW

count

(pOSitions 48-63)

should

specify

a

6-byte

count

field.

If

the

count

is

more

than

six,

the

2841

operates

on the

first

six

bytes

transferred

and,

if

the

CCW SILl

(Suppress

Incorrect

Length

Indicator)

bit

is

zero,

a

Wrong

Length

Record

is

signalled

to

the

CSW.

If

the

CCW count

is

less

than

six,

the

CSW

Unit

Check

bit

is

set,

and a

Sense

I/O

CCW

may

be

used

to identify

the

Seek

Check

and

Command

Reject.

The

six

bytes

specified

must

form

a

valid

address.

At

the

completion

of

a

successful

address

transfer

from

main

storage

to

the

2841, a Channel End

indica-

tion

is

sent

to

the

CSW. A

Device

End

indicator

is

set

in

the

CSW

when the

selected

access

mechanism

has

reached

the

addressed

track.

A Seek

command

need

not

be

preceded

by any

other

CCW.

Seek

commands

operate

in

conjunction

with

the

Set

File

Mask

command.

The

6-byte

seek

address

is

arranged

as

follows:

Device Byte 0 Byte 1 Byte 2 Byte 3

Byte

4 Byte 5

2311

X X X 0-202 X

0-9

cylinder head

2302 X X X 0-249 X 0-45

cylinder head

0-79 X

0-9

2303

X X X cylinder head

2321

X

0-9

0-19

0-9

0-4

0-19

cell sub-cell strip cylinder head

X indicates not used, but all bits

must

be

zero.

Seek.

All

six

seek

address

bytes

referenced

by

the

cCW

are

used

to

determine

seek

address.

Seek

Cylinder.

Only

the

four

low-order

bytes

(bytes 2-5)

referenced

by the CCW

are

used

to

de-

termine

seek

address.

With

the

2321, only

bytes

4

and 5

are

used.

Seek Head. Only the two

low-order

bytes

(bytes 4

and

5)

referenced

by

the

CCW

are

used

to

determine

seek

address.

With

the

2321, only

byte

5

is

used.

Command Seek Command Code

Decimal Hexadecimal Binary

Seek 07

07

00000111

Seek Cylinder

11

OB

00001011

Seek Head

27

1B

00011011

Set

File

Mask

(Figure

4)

A

Set

File

Mask

command

causes

one

byte

of

data

to

be

transferred

from

main

storage

to

the

2841.

At

the

completion

of

the

transfer,

a Channel

End

and

13

Set

File

Mask

BO

0

7 8

Data

Address

Specifies

CPU

Storage

Location

of

the

Mask

Byte,

At

That

Location

is

Found:

Permit

Write

Commands

All Except

Write

Home Address

and

Write

Record

RO

None

Write

Data

or

Write

Key

&

Data

All

31 32

Count

36

47

48 63

( 0000000000000001)

B3

B4

Permit

Seek

Commands

·0

0 All

0

Seek

Cylinder

or

Seek

Head

0

Seek

Head

None

For

the

2841

Storage

Control,

B2, B5, B6,

and

B7

of

the

mask must

be

zero.

If

these

bits

are

not

zero,

the

mask

is

considered

to

be

invalid

and

a CSW

Unit

Check

signal

is

generated.

A

subsequent

Sense

I/O

command

will

indicate

Command

Reject.

Figure

4.

Set

File

Ma;k

Device

End

signal

are

sent

to

the

CSW.

The

byte

of

data

that

is

sent

to

the

2841

describes

the

Write

and

Seek

functions

that

can

be

performed

in

the

CCW

chain.

Set

File

Mask

can

be

issued

anyplace

within

a CCW

chain.

At

the

completion

of

the

CCW

chain,

the

File

Mask

is

reset

to

all

zeros.

If

a

Seek

or

Write

command

is

issued

which

violates

the

File

Mask,

the

command

is

not

execu-

ted,

and a

Unit

Check

signal

is

generated

in

the

CSVil

Status

Byte.

A

subsequent

Sense

I/O

command

sig-

nals

File

Protect

and

Command

Reject

if

the

gener-

ation

was

a

write.

For

a

seek

operation,

File

Pro-

tect

is

set;

for

a

write

operation,

both

File

Protect

and

Command

Reject

are

set.

A

Set

File

Mask

command

can

be

issued

only

once

within

any

given

CCW

chain.

If

an

attempt

is

made

to

issue

more

than

one

Set

File

Mask

command

with

a

given

CCW

chain,

a Unit

Check

signal

is

generated

in

the

CSW

Status

Byte.

A

14

subsequent

Sense

I/O

command

indicates

Command

Reject

and

Invalid

Sequence.

Space

Record

This

command

enables

the

2841

to

pass

over

the

on

a

track.

It

allows

the

2841

to

retrieve

subsequent

records

from

a

track

when

the

Count

Area

of

a

preceding

record

is

not

readable.

The

execution

of

the

Space

Record

command

causes

the

2841

to

search

for

the

Marker

on

the

track.

Upon

detection

of

the

Address

Marker,

Channel

End

and

Device

End

signals

are

genera~ed.

Thus,

the

following CCW

searches

for

the

Address

Marker

following

the

one

detected

by

the

Space

Record

command.

When a Space

Record

command

follows a

Search

HA

or

Read

HA

CCW

~

the

search

for

an

Address

Marker

is

suspended

and

Channel

End and

Device

End

signals

are

generated

immediately.

The

effect

of

this

sequence

is

to

cause

Record

RO

to

be

passed

over.

The

Space

Record

command

does

not

detect

a

Missing

Address

Marker.

However,

if

an

Address

Marker

is

missing,

it

is

detected

on

all

valid

com-

mands

chained

from

the

Space

Record

command

except

Search

ID

commands.

The

Space

Record

command

must

be

chained

from

either

a

Search

or

a

Read

command.

Space Record Command Code

Decimal Hexadecimal Binary

15

OF

00001111

Transfer

In

Channel (TIC)

The

Transfer

in

Channel

command

provides

chaining

between

CCWs

not

located

in

adjacent

CPU

storage

locations.

The

is

fetched

from

the

loca-

tion

specified

by

the

Data

Address

field

of the TIC

CCW.

TIC

does

not

initiate

any

channel

I/O

operation

and

the

I/O

device

is

not

signalled

that

this

command

is

being

executed.

TIC

may

not

be

the

first

CCW

designated

by a

CAW. One TIC

command

may

not

transfer

directly

to

a

second

TIC

command.

When

either

of

these

errors

is

detected

or

when

an

invalid

address

is

specified

in

Transfer

in

Chan-

nel,

the

program-check

condition

is

generated.

De-

tection

of

these

errors

during

data

chaining

causes

the

operation

of

the

I/O

device

to

be

terminated,

whereas

during

command

chaining

they

cause

an

interruption

condition

to

be

generated.

Bit

positions

0-3

and 32-63

are

ignored.

Bits

29-31

must

be

zero

to

meet

the

boundary

require-

ments

for

double

words.

TIC Command Code

Decimal Hexadecimal Binary

X8

XXXXIOOO

Positions

Marked

"X"

Are

Ignored

Sense

I/O

Commands

Four

bytes

of

sense

condition

information

are

pro-

vided

by

the

2841

to

identify

the

setting

of

the

Unit

Check

bit

in

the

CSW

Status

Byte.

These

Sense

Bytes

are

transferred

to

the

Channel

by

a

Sense

I/O

com-

mand.

The

Data

Address

portion

of

the

CCW

directs

the

bytes

to a

specific

CPU

storage

location.

Sense

I/o Command Code

Decimal H exadec i

ma

I Binary

04 04

0000 0100

The

significance

of

a

"1"

condition

for

each

bit

is:

Byte Bit

Designation

o o

o

0 2

0 3

0 4

0 5

Command

Reject

Intervention

Required

Bus

Out

Parity

Check

Equipment

Check

Data

Check

Overrun

Significance

of

"1"

Indicates

that

the

2841

has

received

an

invalid

operation

code,

an

in-

valid

sequence

of

commands,

an

invalid

Seek

Address*,

or

a

file

mask

is

violated

on

a

write

com-

mand.

(See

Set

File

Mask.

)

Indicates

that

the

specified

file

is

not

physically

attached

to

the

system

or,

if

physically

attached

to

the

system,

it

is

not

available

for

use

because

the

file

motor

is

not

on,

a

cover

interlock

is

open,

etc.

Indicates

that

the

2841

has

detected

a

parity

error

during

the

transfer

of

a

command

or

data

from

the

chan-

nel

to

the

2841.

A

parity

error

detected

during

command

transfer

signals

a

Parity

Check,

not

a

Com

...

mand

Rej

ect.

Indicates

that

an

unusual

condition

is

detected

in

the

control

or

storage

unit.

Conditions

covered

by

this

bit

are

defined

by

Sense

Byte

2.

Indicates

that

a

data

error

has

been

detected

in

the

information

re-

ceived

by

the

2841

from

the

storage

unit.

Indicates

that

a

chained

CCW

was

issued

but

that

it

was

received

too

late

to

be

properly

executed;

or

that

a

byte

was

received

during

Reading

or

Writing;

or

that

a

byte

was

received

too

late

(during

a

read

or

write

operation)

to

be

executed

properly.

*A

track

condition

interrupt

on

an

overflow

record

occurs

during

a

write

command.

15

Byte Bit

Designation

Significance

of

11111

o 6

o 7

o

2

3

4

16

Track

Condition

Check

Seek

Check

Count

Area

Check

When

Writing,

the

remaining

por-

tion

of

the

record

area

will

be

filled

with

valid

zeros

and

the

Overrun

check

will

be

generated.

When

Reading,

the

remaining

portion

of

the

record

will

continue

to

be

read

into

the

2841

and

the

Overrun

Check

will

be

generated.

Indicates

defective

track.

Indicates

that

the

file

has

been

un-

able

to

complete

a

Seek

because:

1.

Transferred

Seek

address is

out-

side

the

v.!lid address

boundaries

of

the

storage

device.

Unused

seek

address bytes

must

be

a

valid

address for

the

device

selected.

Command

Rej

ect

is

also

set.

2.

Less

than

six

seek

address

bytes

were

sent.

Equipment

failed

which

resulted

in

the

access

mech-

anism

going

to

either

the

inner

or

outer

stop.

In

this

case

Command

Rej

ect

is

not

set.

Indicates

that

a

data

error

has

been

detected

in

a

Count

Area

read

from

the

storage

device.

Data

Check

(bit

4)

in

Byte 0 is

also

tumed

on.

Error

detection

is

the

same

as

described

for

Data

Check.

Track

Overrun

Indicates

that

writing

has

not

been

completed

by

the

time

the

Index

Point

is

detected.

This

type

of

error

is

created

during a

Write

RO

or

Write

Count,

Key,

and

Data

operation.

Cylinder

End

Invalid

Sequence

No

Record

Found

Indicates

that

the CCW

Command

Chain

has

not

been

completed,

and

Cylinder

End has

been

detected.

Indicates

that

an

attempt

has

been

made

to

execute

an

invalid

sequence

of

CCWs

or

that

two

Set

File

Mask

commands

appear

in

the

same

command

chain.

Valid

command

sequences

are

de-

fined

in

the

individual

command

descriptions.

Command

Rej

ect

(Byte 0

bit

0)

is

also

set

when

an

invalid

sequence

is

detected.

Indicates

that

while

executing

a

chain

of

CCWs,

the

2841

has

detected

two

Index

Points

without

completing

an

intervening

command

to

read

or

Byte Bit

Designation

Significance

of

11111

write

the

Data

Area,

Read

Home

Address,

or

Read

RO.

It

is

also

set

in

conjunction

with

Missing Address

Marker

if

there

is

no

data

on

the

track.

No

Record

Found

is

never

set

if

the

Multi-Track

bit

in

the

command

(Bit

0)

is

on.

5

File

Protected

Indicates

that

a

Seek

or

Write

CCW

6

7

was issued

contrary

to

the

file

mask.

The

Command

Reject

bit

is

also

set

by

this

condition,

if

the

operation

is a

write

operation.

Missing

Ad-

A missing Address

Marker,

which

dress

Marker

may

indicate

a missing

record

is

detected

during

the

execution

of

command

or

chain

of

commands

which

operates

on

successive

Count

Areas

on

a

track.

The

con-

dition

detected

is two

successive

records

on

a

track

with

equal

bit

conditions

in

bit

0

of

the

Flag

bytes,

with

no

intervening

Index

Point.

Overflow

Incomplete

A

missing

Address

Marker

is

also

detected

if

two

Index

Points

are

passed

with

no

intervening

Address

Marker

record

on

the

track.

When

a Missing Address

Marker

is

detected,

this

bitand

bit

4

of

Sense

Byte zero

(Data

Check)

will

be

tumed

on

for

all

commands

or

chained

commands

except

Search

ID CCWs.

The

Search

ID

CCW

may

be

used

to

pass

over

the

Mis-

sing

Address

Marker

so

that

the

re-

maining

data

on

the

track

can

be

retrieved.

Missing Address

Marker

is

set

in

conjunction

with

No

Record

Found

if

there

is

no

data

on

the

track.

This

bit

is

used

with

the

Record

Overflow

special

feature.

It

is

set

with

other

indicators

to

signal

conditions

as follows:

Condition

Sets

Overflow

Incomple.te

and

Other

Indicator:

Overflow

to

a

Track

Condition

defective

track

(Byte

0,

bit

6)

Overflow

from

an

alternate

track

Track

Condition

(Byte

0,

bit

6)

Byte Bit

Designation

Significance

of

"1

II

7 Overflow

Overflow

to

File

Protected

Incomplete

File

Protected

(Byte

1,

bit

5)

boundary

Command

Rej

ect

(Byte

0,

bit

0)

Overflow

to

Set

for

write

only.

wrong

track

Seek

Check

(Head

number

(Byte

0,

bit

7).

unequal)

A

Track

Condition

check

is

generated

under

the

following

conditions:

1.

If

an

overflow

record

is

being

read,

written,

or

searched

which

overflows

to a

defective

track.

The

interrupt

occurs

after

the

last

byte

on

the

has

been

oper-

ated

on

and

before

the

first

byte

for

the

de-

fective

track

is

requested

from

or

sent

to

the

channel.

In

this

case

Overflow

Complete

is

also

set.

Command

Reject

is

also

set

if

the

operation

was

a

write.

2. A

Search

HA,

Read

HA,

or

Read

RO

causes

a

head

switch

to

a

defective

track

during

a

multiple

track

operation,

when

a

Search

operation

other

than

Search

HA

is

attempted.

The

interruption

occurs

prior

to

transfer

of

any

data

to

or

from

the

channel.

Write

commands

never

set

track

con-

dition

checks.

Sense

Bytes

2 and 3.

These

bytes

are

provided

to

assist

the

Customer

Engineer

when

using

diagnostic

programs

to

locate

equipment

malfunctions.

Device

Reserve

(Two-Channel Switch

Special

Feature)

Without

the

Two-Channel

Switch

feature

installed,

Device

Reserve

is

rejected

by

the

2841 and

the

Unit

Check

bit

in

the

CSW

Status

Byte

is

set.

The

Com-

mand

Reject

bit

in

Sense

Byte

0

is

set

to

indicate

what

caused

the

Unit Check

condition.

With

the

Two-Channel

Switch

feature,

a

Device

Reserve

command

causes

the

addressed

device

to

be

reserved

to

the

channel

issuing

the

command.

The

device

then

remains

reserved

to

the

same

channel

until

that

channel

executes

a

Device

Release

command

addressed

to

the

specific

device,

or

until

the

CPU

is

.reset.

A

Device

Reserve

command

is

rejected

with

a

Busy

indication

in

the

CSW

if

any

normal

Busy

con-

dition

exists.

However,

a

Device

Reserve

command

is

executed

regardless

of

any

abnormal

file

status

condition,

such

as

off-line,

unsafe,

etc.

A

Device

Reserve

command

is

rejected

when a

Set

File

Mask

command

precedes

it

in

the

same

command

chain.

The

Unit Check

bit

in

the

CSW

is

set

when

the

command

is

rejected,

and

the

Command

Reject

and

Invalid

Sequence

bits

are

set

to

indicate

the

conditions

which

caused

the

Unit

Check.

The

Device

Reserve

command

performs

all

of

the

functions of a

Sense

I/O

command

in

addition

to

the

functions

described

in

this

section.

Device

Reserve

Command Code

l>ecimal Hexadecimal Binary

180

54

1011

0100

Device

Release

(Two-Channel Switch

Special

Feature)

Without

the

Two-Channel

Switch

feature

installed,

Device

Release

is

rejected

by

the

2841

and

the

Unit

Check

bit

in

the

CSW

Status

Byte

is

set.

The

Com-

mand

Reject

bit

in

Sense

Byte

0

is

set

to

indicate

what

caused

the

Unit Check

condition.

With

the

Two-Channel

Switch

feature,

a

Device

Release

command

terminates

the

reservation

of

the

addressed

device

to

the

channel.

This

command

is

rej

ected

with

a

Busy

indication

in

the

CSW

if

any

normal

busy

conditions

exists.

However,

a

Device

Release

command

is

executed

regardless

of any

ab-

normal

file

status

condition

such

as

off-line,

unsafe,

etc.

A

device

is

normally

reserved

to

a

particular

channel

whenever

that

channel

exectues

a

Device

Re-

serve

command.

The

device

remains

reserved

to

the

same

channel

until

that

channel

causes

the

2841

to

execute

a

Device

Release

command,

or

until

the

CPU

is

reset.

A

Device

Release

command

is

rejected

when a

Set

File

Mask

command

precedes

it

in

the

same

com-

mand

chain.

The

Unit

Check

bit

in

the

CSW

is

set

when

the

command

is

rejected,

and

the

Command

Reject

and

Invalid

Sequence

bits

in

the

Sense

Bytes

are

set

to

indicate

the

conditions

which

caused

the

Unit

Check.

A

Device

Release

command

performs

all

of

the

functions of a

Sense

I/O

command

in

addition

to

the

functions

described

in

this

section.

See

Two-Channel

Switch

for

additional

informa-

tion.

Device

Release

Command Code

Decimal Hexadecimal Binary

148

94

1001

0100

17

Search

Commands

On

all

Search

operations,

the

Channel

operates

in

the

Write

mode while

the

storage

unit

operates

in

the

Read

mode. The 2841

compares

the

information

coming

from

CPU

storage

and the

information

com-

ing

from

the

storage

unit.

If

the

search

condition

is

satisfied,

a

status

modifier

indication

is

sent

to

the

CSW

and

the

chan-

nel

fetches

the

in

the command

chain

from

a

position

sixteen

positions

higher

than

the

current

(Search) CCW.

This

allows modification

of

a

com-

mand

chain

as

a function of

the

data

recorded

on

the

direct

access

device.

On

all

Search

commands,

Command Code

bit

0

determines

whether

this

is

to

be

a multiple

track

operation;

that

is,

whether

switching

to

the

head

in

the

cylinder

is

to

occur

when the

Index

Point

is

detected.

If

bit

O.

is

not

set

(0),

head

switching

does

not

take

place;

if

bit

0

is

set

(1),

head

switching

does

take

place.

If

head switching

has

occurred,

the

will

be

used

if

the

Search

Command

is

repeated.

This

allows

for

se-

quential

searching

of

an

entire

cylinder

by

repeating

the

Search

Command once

for

each

record

to

be

searched.

The following command

chain

illustrates

the

procedure

for

reading

a

record

identified by a key

stored

at

location

a

in

the

CPU.

Command

Chain

Search

Key a

TIC

*-8

Read

Data

f3

Function

Compare

Key with

Search

Argument

Transfer

Back

to

Search

Read

Data

Area

if

Status

Modifier

was

Returned

from

Search

The channel

is

busy

during

a

search

operation.

18

Search

Home

Address

Equal

(Search

HA)

This

command

causes

the 2841 to

search

for

the

Index

Point,

then

compare

four

bytes

of

Home

Ad-

dress

data

(CCHH) coming

from

main

storage

with

four

bytes

of Home

Address

data

coming

from

the

storage

device.

The

Flag

byte

is

not

transferred

or

compared

during

this

command.

If

a

logical

comparison

is

equal,

a Channel End,

Device

End,

and

Status

Modifier signal

is

generated

in

the

CSW

status

byte.

If

the

logical

comparison

is

lUlequal,

then

a Channel End and Device End

are

generated.

Search

Home

Address

does

not

generate

a

No

Record

Found

signal

if

.the

specified

Home

Address

is

not

found.

If

the CCW Count

is

greater

than

four

bytes,

the

Search

operation

is

completed when the 2841 count

equals

zero.

The

2841

terminates

the

command

with

a Channel End and Device

End.

The

Status

Modifier

is

generated

if

the

logical

comparison

was

satisfied.

If

the CCW Count

is

less

than

four

bytes,

the

logical

comparison

between the

data

coming

from

CPU

Storage

and the

data

coming

from

the

storage

unit

continues

until

the CCW Count

reaches

zero.

At

the

time

the

2841 count

reaches

zero,

a Channel End

and Device End

are

generated.

A Status

Modifier

is

generated

if

the

search

condition

was

satisfied

on

the

short

field.

If

a

Parity

Check,

Overrun,

or

Data

Check

is

detected,

Unit Check, Channel End, and Device End

signals

are

generated

in the

CSW

at

the

completion of

the

command.

A

Search

Home

Address

command

does

not

have

to

be

preceded

by any

other

CCW

in

order

to

be

exe-

cuted.

Search

Identifier

(Search

ID)

Search

ID

commands

(Figure

5)

cause

a

comparison

to

be

made

between

five

bytes

of

data

from

CPU

storage

and the five byte

record

identifier

portion

of

a count

area

from

the

storage

unit.

Record

Identifier

--------~~------

----

....

---~-----------

Count

Area

~

The ID to

be

searched

is

the

ID

of

the

record

following the

Marker

or

Index point,

in

which

case

ij.0

is

searched.

If

the

CCW count

is

greater

than

five

bytes,

the

Search

operation

is

completed when the 2841

count

equals

zero.

The

2841

terminates

the

command

with

a Channel End and Device End. The Status Modifier

is

generated

if

the

logical

comparison

was

satisfied.

If

the

CCW count

is

less

than

five

bytes,

the

logical

comparison

between

the

data

coming

from

core

storage

and

the

data

coming

from

the

file

con-

tinues

until the CCW

COlUlt

reaches

zero.

When the

2841 count

reaches

zero,

a Channel End and Device

End

are

generated.

A

Status

Modifier

is

generated

if

the

Search

condition

was

satisfied

on the

short

field.

Command Search I D Command Code

Decimal Hexadecimal Binary

Search

ID

Equal 49

31

00110001

Search I D

High

81

51

01010001

Search I D Equal

or

High

113

71

01110001

Command Search ID

Multiple

Track Command Code

Decimal Hexadecimal Binary

Search I D

Equa

I

177

B1

10110001

Search

ID

High 209

D1

11010001

Search I D Equal

or

High

241

F 1 11110001

Figure

5.

Search

Command

Codes

If

a

Parity

Check,

Overrun,

or

Data

Check

is

detected

during

a

Search-ID

operation,

Unit

Check,

Channel

End,

and

Device

End

signals

are

generated

at

the

completion

of

the

command.

A

Search

ID

command

does

not

have

to

be

pre-

ceded

by

any

other

CCW

in

order

to

be

executed.

If

Command

Code

bit

°

(multiple

track)

is

0,

the

search

is

confined

to

one

track

and

can

be

re-

peated

until

either

the

Search

Condition

is

satisfied

or

until two

Index

Points

are

sensed;

at

which

time

Unit

Check

(No

Record

Found),

Channel

End,

and

Device

End

signals

are

generated.

If

the

multiple

track

bit

is

a 1,

the

search

can

be

repeated

until

the

Search

Condition

is

satis-

fi~d

or

until

the

End-of-Cylinder

is

detected.

At

this

time

a

Unit

Check

(End-of-Cylinder)

signal

is

generated.

Search

ID

Equal.

If

a

logical

comparison

on

equal

is

encountered,

Channel

End,

Device

End,

and

Status

Modifier

signals

are

generated.

If

the

logical

comparison

is

unequal,

Channel

End

and

Device

End

signals

are

generated.

18. 1

Searcl;t. ID High.

This

command

operates

in a

manner

similar

to

that

of

the

Search

ID Equal

command,

ex-

cept

that

the

comparison

is

made

for

a high condition.

The

high condition

indicates

that

the

ID

on

the

Storage

Unit

is

higher

than

the

ID

in

main

storage.

The

com-

parison

is

made

byte by

byte.

Search

ID

Equal

or

High.

This

command

operates

in

a

manner

similar

to

that

of

the

Search

ID

Equal

com-

mand

except

that

the

comparison

is

made

for

either

an

equal

or

high

condition. The

equal

or

high

con-

dition

indicates

that

the

ID

on

the

storage

device

is

equal

to

or

higher

than

the

ID

in

main

storage.

Search

Key

Execution

of

a

Search

Key

command

causes

a

com-

parison

to

be

made

between

bytes

of

data

from

main

storage

and a Key

from

the

storage

device.

The Key

to

be

searched

is

the

Key of

the

record

following

the

Marker.

Search

Key

will

pass

over

RO

unless

chained

from

a

Search

ID

that

has

searched

the

ID

of

RO.

If

the

CCW

countis

greater

than

the

Key length,

the

Search

operation

is

completed

when

the

2841

count

equals

zero.

The

2841

terminates

the

com-

mand

with

a Channel End and Device End. The

Status

Modifier

is

generated

if

the

logical

comparison

was

satisfied.

If

the

CCW count

is

less

than

the

Key

length,

the

logical

comparison

between

data

from

CPU

stor-

age and the

data

from

the

storage

unit

continues

un-

til

the

CCW

count

reaches

zero.

When

the

2841 count

reaches

zero,

a Channel End and

Device

End

are

gen-

erated.

A

Status

Modifier

is

generated

if the

Search

Condition

was

satisfied

on

the

(short)

field.

If a

Parity

Check,

Overrun,

or

Data

Check

is

detected

during

the

Search

-Key

operation,

Unit

Check,

Channel End, and Device End

signals

are

generated

at

the

completion

of

the

command.

A

Search

-Key

command

does

not

have to

be

pre-

ceded

by any

other

CCW in

order

to

be

executed.

If

the

multiple

track

bit

is

0,

the

search

can

be

confined

to

one

track

and

can

be

repeated

until

either

the

search

condition

is

satisfied

or

until

two

Index

Points

are

sensed;

at

which

time

a Unit

Check

(No

Record

Found), Channel End, and Device End

signals

are

generated.

If

the

multiple

track

bit

is

1,

the

search

can

be

repeated

until

either

the

search

condition

is

satisfied

or

until

End-of-Cylinder

is

detected.

If

End-of-Cylinder

is

detected,

an

End-

of-Cylinder

indication

is

generated.

The

Search

Key

command

never

returns

a

Status

Modifier

if

the Key Length of

the

search

record

is

zero.

Search

Key

Equal.

If

a

logical

comparison

on

equal

is

encountered,

Channel End,

Device

End,

and

Status

Modifier

signals

are

generated.

If

the

logical

comparison

is

unequal

or

the

Record

has

no Key

area,

then

Channel End and

Device

End

signals

are

generated.

Search

Key High.

This

command

operates

in a

man-

ner

similar

to

that

of

the

Search-Key

Equal

com-

mand

except

that

the

comparison

is

made

for

a high

condition.

The

high

condition

indicates

that

the

key

in

the

storage

unit

is

higher

than

the

key

in

CPU

storage.

Search

Key

Equal

or

High.

This

command

operates

in a

manner

similar

to

that

of

the

Search

Key

Equal

command

except

that

the

comparison

is

made

for

either

an

equal

or

high condition.

The

equal

or

high

condition

indicates

that

the

key

in

the

storage

unit

is

equal

or

higher

than

the

key

in

CPU

storage.

Command Search Key Command Codes

Decimal Hexadecimal Binary

Search Key Equal

41

29 00101001

Search Key High

73

49 01001001

Search Key Equal

or High

105

69 01101001

Command Search Key Command Codes,

Multiple

Track

Decimal Hexadecimal Binary

Search Key Equal 169

A9

10101001

Search Key High

201

C9

11001001

Search Key Equal

or High 233

E9

11101001

Search

Key and

Data

(File

Scan

Special

Feature)

The

File

Scan

feature

provides

an

automatic

rapid

search

for

a

specific

set

of

conditions.

The

search

is

carried

out

over

both Key

and

Data

areas

of

a

record.

Prior

to

executing

a

File

Scan

operation,

a

"control

mask"

is

set

up

in

main

storage.

The

mask

consists

of

bytes

of

information

on

which

a

comparison

is

or

is

not

to

be

made.

The

bytes

on

which a

comparison

is

not

to

be

made

are

filled

with

l's

prior

to

the

search.

If

an

equal

comparison

is

encountered,

Channel

End,

Device

End,

and

Status

Modifier

signals

are

generated.

If

the

logical

comparison

is

unequal,

only Channel End and

Device

End

signals

are

gener-

ated.

19

If

the

multiple

track

bit

is

off (0), the

search

can

be

confined

to

one

track

until

the condition

is

satisfied

or

until two Index

Points

are

sensed,

at

which

time

Unit

Check

(No

Record

Found), Channel

End,

and Device

End

signals

are

generated.

If

the

multiple-track

bit

is

1,

the

search

can

be

repeated

until

the

specified

condition

is

met

or

until

End-of-

Cylinder

is

encountered,

at

which

time

an

End-of-

Cylinder

signal

is

generated.

No

more

positions

than

the

number

specified

by

the

CCW Count

are

compared.

If

the CCW Count

is

greater

than

Key Length

plus

Data

Length,

the

Search

operation

is

limited

by

the

record

Key and

Data

Lengths.

A

zero

Key Length

causes

comparison

of

data

only.

If

the

channel

count

is

less

than

the

Data

Length

plus

the Key

Length,

a

truncated

search

is

performed.

If

a

Parity

Check,

Overrun,

or

Data

Check

is

detected

during

a

Search

Key and

Data

Operation,

Unit

Check,

Channel End, and Device End

signals

are

generated

at

the

completion

of

the

command.

Search

Key and

Data

Equal.

This

command

causes

the

2841

to

make

a

logical

comparison

on

equal

be-

tween

the

Key and

Data

information

from

the

storage

device

with

the

mask

information

coming

from

main

storage

(Figure

6).

Search

Key and

Data

High.

This

command

operates

in

a

manner

similar

to

that

of

the

Search

Key and

Data

Equal

command

except

that

the

comparison

is

made

for

a high condition. The high condition

indi-

cates

that

the

storage

device

information

is

higher

than

the

mask

information

in

main

storage.

Search

Key and

Data

Equal

or

High.

This

command

operates

in a

manner

similar

to

that

of

the

Search

Key and

Data

Equal

command

except

that

the

com-

parison

is

made

for

an

equal

or

high condition.

The

equal

or

high condition

indicates

that

the

storage

device

information

is

equal

to

or

higher

than

the

mask

information

in

main

storage.

A

File

Scan function

over

an

entire

cylinder

can

be

executed

by

the

sequence

of CCWs given below.

This

sequence

assumes

that

a

Set

File

Mask CCW

was

performed

prior

to

the

Scan

sequence.

20

Command

Remark

1.

Seek

Position Access

*2.

SRCH IDEQ (Previous) find

record

prior

to

beginning

3.

TIC

*-8

*4.

Read

Count

a

*5.

Search

Key

and

Data

EQ

*6.

TIC

*-16

7.

Seek

Head

a

**8.

Search

ID

EQ a

9.

TIC

*-8

**10.

Read

Key

and

Data

*Multiple

Track

Bit

On

**Multiple

Track

Bit

Off

of

scan

area

on

Unequal

Repeat

Search

Read

Count

of

Record

into

a

Scan

Key

and

Data

On

Unequal,

Repeat

steps 4 & 5

Reposition

access

(head

select

only)

Search

for ID

read

in

step

4

On

unequal

repeat

step

8

Read

Key

and

data

Step 4

of

the

sequence

causes

the

Count

infor-

mation

coming

from

the

storage

device

to

be

read

into CPU

storage.

Key and

data

information

from

the

storage

device

are

compared

with

the

mask

in-

formation

from

main

storage

on

step

5. The

com-

paris

on

is

made

based

on

the

condition

specified

by

the

Searcn

Key and

Data

CCW. When

the

specified

condition

is

encountered,

the

program

must

re-

orient

to

the

beginning

of

the

record

with

steps

8 and

9. Then the

desired

key and

data

is

read

in

step

10.

At

each

detection

of Index

Point

in

step

5,

the

head

address

is

incremented

by

one.

As a

result,

step

4

is

done on

the

if

the

searched

was

the

last

one on a

track.

Read

Commands

On

all

Read

commands

the

2841

checks

the

validity

of

each

area

in

a

record

as

the

area

is

transferred

from

the

storage

device.

If

a

Data

Check

or

Overrun

is

detected,

a Unit

Check

signal

is

generated

upon

completion

of the

command

except

when the

error

is

in

the

Count

Area.

The

command

is

terminated

at

the

end

of

the

Count

Area.

At

the

completion

of

the

last

check,

the 2841

sends

Channel End and

Device

End

signals

to

the

channel.

N

....

Search

Key

and

Data Equa I

Search

Key

and

Data High

Search

Key

and

Data Equal or High

Command

Code

Command

Code

Command Decimal Hexadecimal Binary

Search Key & Data Equa I

45

2D

00101101

Search Key & Data High 77 4D 01001101

Search Key & Data Equal 109

6D

01101101

or High

Command

Code

Multiple-Track

Command Decimal Hexadecimal Binary

Search Key & Data Equal 173

AD

10101101

Search Key & Data High 205 CD 11001101

Search Key & Data Equal

237

ED

11101101

or High

Figure

6.

Search

Key

and

Data

Specifies

number of Bytes in

CPU

storage

{including

"Mask

Bytes"

to

be

used as

Search

Argument. If CCW

count

equals

key

length,

command

is

effective-

Count

48

63

Iy

a

"Search

Key."

~

Byte 4

is

not

is

set

to

all

l's

Key

Area

Search

Argument in CPU

Storage

and

8-11

are

not compared

because

of "Mask Bytes" in CPU

storage.

CCW

count

of

20

I

imits search

to

20

position

span.

Data Area

This

example

assumes

CCW

count

20

4 5 6 10

11

12 13 14 15 16 17 18

Key

and

Data Areas From

Storage

Unit

Read

Home

Address

(Read

HA)

This

command

causes

the

2841 to

search

for

the

Index

Point.

Detection

of

the

Index

Point

causes

the

five

bytes

of Home

Address

information

to

be

trans-

ferred

from

the

storage

device

to CPU

storage.

Exactly

five

bytes

are

transferred

including the flag

byte.

If

the channel

count

is

less

than five, only

that

number

of

bytes

is

transferred.

Chaining

requirement:

None

Read

HA Command Code

Decimal H exadec i

ma

I Binary

26

1A

00011010

Read

HA

Command Code

Multiple

Track

Decimal Hexadecimal Binary

154

9A

10011010

Read

Count

This

command

causes

the

eight

bytes

of

the Count

Area

following the

Marker

(AM)

to

be

transferred

from

the

storage

device

to

main

storage.

The

number

of

bytes

of

information

to be

read

is

always

eight.

If

the channel

COlIDt

is

less

than

eight,

only

that

number

of

bytes

is

transferred.

Chaining

requirement:

None. The Count

Area

of

RO

cannot

be

read

by a

Read

Count command.

Read

Count Command Code

Decimal Hexadecimal Binary

18

12

00010010

Read

Count Command Code,

Multiple-Track

Decimal Hexadecimal Binary

146 92 10010010

Read

Track

Descriptor

Record

(Read

RO)

This

command

causes

the

2841 to

search

for

Index

Point.

Detection

of

Index

Point

causes

the

2841 to

"count

off"

to

Home

Address

and the following gap.

When

these

Areas

have

been

traversed,

record

RO

(Count, Key and Data)

is

transferred

from

the

stor-

age

device

to

main

storage.

Chaining

Requirement:

None. A

Read

RO

command

chained

from

a

Search

HA

or

Read

HA

is

22

executed

immediately

and

does

not

cause

a

search

for

Index

Point.

Read

RO

Command Code

Decimal Hexadecimal Binary

22

16

00010110

Read

RO

Command Code,

Multiple-Track

Decimal H exadec i

ma

I Binary

150 96 10010110

Read

Data

(Figure

7)

This

command

causes

the

Data

Area

of a

record

to

be

transferred

from

the

storage

device

to

main

stor-

age.

Read

Key and

Data

This

command

causes

the Key and

Data

areas

of

a

record

to

be

transferred

from

the

storage

device

to

main

storage.

If

Key Length

is

zero,

this

command

operates

like

a

Read

Data

command.

The

record

from

which the

Data

or

Key and

Data

is

read

is

dependent upon

the

ation.

Read

Count, Key, and

Data

(Figure

8)

This

command

causes

the

entire

record

(Count, Key,

and Data) following the

to

be

transferred

from

the

storage

device to

main

storage.

Record

RO

is

bypassed

as

it

is

not

preceded

by

an

address

mark.

Chaining

requirements:

None.

Write

Commands

Write

commands

cause

data

to

be

transferred

from

main

storage

to the

storage

device.

During

the

transfer,

the 2841 adds

appropriate

Cyclic Check

bits

to

each

area

written.

At the completion

of

the

command,

Channel End and Device End

signals

are

sent

to the channel.

Format

Write

Commands

The following

are

Format

Write

commands:

Write

Home

Address

Write

RO

Write

Count, Key and

Data

Read

Data

Read Key

and

Data

Command

Code

o 7 8

Data

Address

Specifies

CPU

storage

locations

to

which

key

or key

and

data

fields

are

to

be

transferred.

After

the

command

is

executed,

CPU

storage

contains:

.

Figure

7.

Read

Data

and

Key

and

Data

Read

Count,

Key

and

Data

Command

Code

o 7 8

Data

Address

Specifies

CPU

storage

location

to

which

count,

key,

and

data

areas

are

to

be

transferred,

after

trans-

fer,

CPU

storage

contains:

Key

Area

•

Specified

Location

Count

Specifies

number

of

bytes

to

be

transferred.

May

be

less

than

entire

data

or

key

and

data

length.

63

Data

Area

48

Count

63

Specifies

number

of

bytes

to

be

transferred

to

CPU

storage,

may

be

less

than

entire

record

length.

I

~

__

~:

__

~

___

~~o_u_n~~_A_re_~~~

__

~

__

~

__

K_e_y~~

Area

Data

~L.

__

A_re_a

__

..1

Read

Data

Command

Codes

Decimal

Hexadecimal

Binary

Read

Data

06

00000110

Read Key &

Data

14

OE

00001110

Read

Count,

Key

&

Data

30

IE

00011110

Read

Data

Command

Codes,

Multiple

Track

Decimal

Hexadecimal

Binary

Read

Data

134

86

10000110

Read Key &

Data

142

8E

10001110

Read

Count,

Key

&

Data

158

9E

10011110

Figure

8.

Read

COWlt, Key,

and

Data

23

These

commands

are

used

to

initiaJize

tracks

or

records.

A

command

chain

which

includes

one

or

more

Format

Write

commands

must

include an

appro-

priate

Set

File

Mask CCW

preceding

it.

After

the

last

Format

Write

command

in

a

chain

has

been

completed,

and Channel End and Device

End

sigrials

generated,

the

2841

causes

the

remain-

ing

portion

of

the

track

to

be

erased.

If

a new

com-

mand

chain

is

initiated

before

the

end

of

the

track

is

reached,

a

Control

Unit

Busy

signal

is

generated

in

the

CSW.

At

the

end

of

the

track,

Control

Unit End

is

signalled

to

the

channel.

If

a

command

other

than

a

Format

Write

is

chained

from

a

Format

Write

command,

the

2841

retains

and

executes

it

after

the

track

has

been

erased

and Index

Point

is

detected.

Detection

of

a

Parity

Check

on

an

Overrun

dur-

ing

a

Format

Write

operation

causes

a

Unit

Check

to

be

signalled

at

the

end

of

the

operation.

The 2841

writes

valid

zeros

from

the

time

the

Overrun

is

de-

tected

to

the

end

of

the

record.

The Cyclic

Check

bits

written

in

this

case

may

not

be

valid.

Write

Home

Address

(Write HA).

This

command

causes

the 2841 to

search

for

the

Index

Point

(Fig-

ure

9). When

the

Index

Point

is

detected,

the

speci-

fied

data

is

transferred

from

main

storage

to

the

storage

device.

The

2841

transfers

five

bytes

of

Write

HA

Command

Code

o

Index

Marker

7 8

Data

Address

Specifies

CPU

storage

location

from

which

five

,bytes

of

home address

are

to

be

transferred.

Cylinder

2Number

Home Address

Head

Number

4

Write

Home Address Command

data

from

the

CPU,

and adds two

bytes

of

Code

Check. At

this

point, Channel End and Device End

signals

are

generated.

If

the

dcw Count

is

less

than

five,

the

2841

records

valid

zeros

until

five

bytes

have

been

writ-

ten.

If

the CCW Count

is

greater

than

five, the 2841

transfers

only

the

first

five

bytes

from

CPU

storage.

A

Write

HA

command

is

normally

used

to

establish

track

identity within a

storage

device.

Each

track

must

be

initialized

with

a Home

Address

before

a

data

operation

which

involves

that

track

can

take

place.

Chaining

Requirements:

Execution

of

this

com-

mand

is

dependent upon a

correct

Set

File

Mask

.

command

preceding

it

in

the

same

command

chain.

Write

Track

Descriptor

Record

(Write

RO).

This

command

causes

specified

data

to

be

transferred

from

main

storage

to

the

storage

device

(Figure

10).

The

first

eight

bytes

transferred

from

core

make

up the Count

Area.

The

Flag

byte

is

gener-

ated

by the 2841.

The

remaining

data

is

written

in

the Key and

Data

Areas

as

specified

by

Key Length

and

Data

Length

in

the

Count

Area.

The 2841

writes

the

correct

Code

Check

at

the

end

of

each

Area.

Channel End and Device

End

signals

are

generated

after

the Code

Check

of

the

Data

Area

has

been

written.

000

48

Cyclic

~heck

Count

Usually

5

(0000000000000101)

63

Decimal I

Hexadecimal

I Binary

25

19

0001

1001

Figure

9.

Write

HA

24

Write

RO

Command

Code

o 7 8

Figure

10.

Write

RO

Data

Address

Specifies

CPU

storage

location

from

wh

i

ch

count,

key,

and

data

bytes

are

to

be

transferred.

Key

and

data

field

lengths

are

specifi

ed

in

the

count

area.

Head

No.

Rec.

Key Dota

No.

Len. Length

Count

Area

The

CCW

Count

Field

specifies

the

number

of

bytes

to

be

transferred

from

main

storage

by

the

channel.

This

is

eight

(bytes)

plus

Key

Length

plus

Data

Length.

If

CCW

Count

is

less

than

this,

the

2841

writes

valid

zeros

so

that

the

Key

and

Data

Areas

conform

to

the

lengths

specified

in

the

record

Count

Area.

Chaining

Requirements:

This

command

causes

an

Invalid

Sequence

signal

to

be

generated,

unless

it

is

chained

from

a

Search

HA

that

was

equal

on

all

five

bytes

of the Home

Address,

or

from

a

Write

HA.

If

the

Write

RO

CCW

is

issued

more

than

60

microseconds

after

the

preceding

Search

HA

or

Write

HA,

an

Overrun

signal

is

generated.

Write

Count, Key, and

Data

(Figure

11).

This

com-

mand

is

the

same

as

the

Write

RO

except

that

the

2841

causes

an

Address

Marker

to

be

written

on

the

track

immediately

before

the Count.

This

command

causes

an

Invalid

Sequence

Signal

to

be

generated

unless

it

is

chained

from

a

Write

RO,

another

Write

Count, Key and

Data,

or

from

a

suc-

cessful

Search

Equal

ill

or

Search

Equal

Key

com-

mand.

This

search

must

not

be

a

truncated

search,

or

one

in

which

the

CCW

count

is

less

than

the

length

of

the

area.

A

Read

Data

or

Read

Key and

Data

CCW

may

be

inserted

between

a

Search

CCW and

Write

Count, Key

and

Data

CCW.

Gap

Key

Area

48

Count

Specifies

total

RO

field

lengths

count

(eight

bytes),

plus

key

length,

plus

data

length.

Write

RO

Command

Code

Hexadecimal

Binary

63

15

0001

0101

Gap

Dota

Area

Write

Special

Count,

Key,

and

Data

(Figure

12).

This

command

functions

like

the

Write

command

except

that

it

causes

a

one-bit

to

be

placed

in

bit-

position

one of

the

Flag

byte

when

the

2841

generates

and

writes

the

Flag

byte.

It

is

used

with

the

Record

Overflow

feature.

Data

Write

Commands

These

commands

are

used

for

normal

record

up-

dating.

Detection

of

a

Parity

Check

or

Overrun

causes

a

Unit

Check

to

be

generated

at

the

comple-

tion

of

the

command.

A

data

check

which

occurs

in

record

areas

which

must

be

passed

over

but

not

written,

terminates

the

command

before

data

is

written.

Write

Data.

This

command

causes

the

specified

data

to

be

transmitted

from

CPU

storage

to

the

storage

device.

Writing

continues

as

specified

by

the

Data

Length

portion

of

the

Count

Area.

At

this

point,

the

2841

causes

the

Code

Check

to be

written

and

then

sets

Channel

End

and

Device

End.

If

the

CCW

Count

is

less

than

the

Data

Length

in

the

Count

Area,

the

2841

causes

valid

zeros

to

be

written

in

the

remaining

portion

of

the

Data

Field.

Chaining

Requirement:

Write

Data

causes

an

Invalid

Sequence

to

be

generated

if

it

is

not

chained

25

Write

Count,

Key

and

Data

Command

Code

o

Address

Marker

7 8

Address

Specifies

CPU

storage location

from

wh

iCh

count, key,

and

data

bytes

are

to

be

transferred.

Key

-cirid

data field lengths

are

specified

in the count

area.

Flag

Cylinder

No.

Head

No.

Rec. Key

No.

Len.

Count

Area

Figure

11.

Write

Count,

Key

and

Data

Write

Special

Count,

Key, and Data

Command

Code

Data Address

o 7 8

Address

Marker

(

Cylinder

No.

'III

Specifies

CPU

storage location

from

wh

ich count, key, and

data

bytes

are

to

be

transferred.

Key

and

data

field lengths

are

specified

in

the

count

area.

I

Fla

g

Cylinder

No.

Head

No.

Count

Area

Figure

12.

Write

Special

Count,

Key,

and

Data

26

Gap

Key

Area

48

Count

Specifies

total

of

all

field

lengths;

count

{eight bytes}, plus key

length,

plus

data

length

63

Write Count Key,

and

Data

Command

Decimal

29

Hexadeci

rna

I Binary

10

00011101

Gap

Data Area

Count

Specifies

total

of

all

field

lengths; count

(eight bytes), plus key

length,

plus

data

length

63

Write

Special

Count,

Key

and

Data Command

Code

Decimal

01

Hexadecimal

01

Binary

00000001

from

a

successful

Search

Equal

ID

or

from

a

Search

Equal

Key

command

which

was

not

truncated.

Write

Key and

Data.

This

command

is

the

same

as

a

Write

Data

command

except

that

the

Key

Area

is

also

written.

If

the

Key

Length

Field

of the

Count

Area

is

zero,

the

Write

Key

and

Data

command

func-

tions

just

like

the

Write

Data

command.

Write Data

Write Key

and

Data

Data Address

~--------~~~--------~

~

Specifies

CPU

storage

location'

I The CCW

count

field

specifie;

from which

data

or key

and

the

number

of

bytes to be

data

fields

are

to

be

transferred.

Write Data Command Codes

Decimal Hexadecimal Binary

Write

Data

05

00000101

Write Key & Data

13

00

00001101

An

Invalid

Sequence

is

generated

if

Write

Key

and

Data

is

not

chained

from

a

successful

Search

Equal

ID

command,

which

was

not

truncated.

Write

commands

are

never

truncated.

End

of

File

The

end

of

a

logical

file

is

indicated

by

a

record

whose

Count

Area

contains

a

Data

Length

of

two

bytes

of

zeros.

This

may

be

any

record

on a

track.

This

record

is

written

by

a

Write

Count,Key

and

Data

CCW

or

a

Write

RO.

The

indicated

zero

Data

Length

causes

the

2841

to

record

a

Data

Area

of

a

single

zero

byte.

Formation

of

a Key

Area

in

an

end-of~file

record

depends

on

the

indicated

Key

Length.

If

Key

Length

is

not

zero,

the

Key

Area

is

transferred.

As

a

logical

file

is

read

or

written,

the Count

Area

of

each

record

is

examined.

Detection

of

a

zero

Data

Length

causes

Unit

Exception

to

be

sig-

nalled

in

the

Channel

Status

Word

at

the

completion

time

of

the

read

or

write

operation

that

is

performed.

No

part

of

the

Data

Area

is

transferred.

Record

Rn

Key

~

Area

I

..

oct.Q

....

1.

Area

10

End-of-File

Record

Multiple

Track

(M

-T)

Operation

The

2841

has

the

ability

to

automatically

select

the

numbered

head

on

an

access

mech-

anism

under

control

of

bit

0

(BO)

of

the

Command

Byte. Head

switching

does

not

take

place

at

Index

Point

if

BO

is

a

zero.

Head

switching

takes

place

at

Index

Point

if

BO

is

a 1.

The

M

-T

bit

is

recognized

on

all

Read

and

Search

commands.

Therefore,

a

certain

amount

of

discretion

should

be

used

when

making

BO

a I

bit.

For

example,

if

during

a

Search

operation

the

M-T

bit

is

a 1

and

index

is

encountered

before

the

search

condition

is

satisfied,

the

head

automatically

switches

to

the

The

operation

continues

until

the

End-of-Cylinder

is

detected.

This

condi-

tion

can

occur

if

the

search

was

initiated

beyond

the

point

where

the

record

was

located

on

the

track.

On

the

other

hand,

by

correctly

utilizing

the

M-T

bit,

it

is

possible

to

search

a

complete

cylinder

of

IDs

or

Keys.

Two-Channel Switch (Special

Feature)

The

Two-Channel

Switch

feature

provides

the

ability

for

the

2841

Storage

Control

to

be

shared

by

two

channels

and

also

allows

individual

devices

(access

mechanisms)

to

be

reserved

for

the

exclusive

use

of

either

of

the

channels.

The

two

channels

may

be

attached

to

the

same

CPU

or

different

CPUs.

Chan-

nel

switching

and

device

reservation

in

the

2841

are

performed

under

control

of

the

system

program.

The

Two-Channel

Switch

feature

is

limited

to

eight

access

mechanisms.

Channel

Selection

Switch

This

switch

has

three

positions:

Channel

A,

Channel

B,

and

neutral.

With

the

switch

in

the

neutral

position,

the

2841

is

selected

by

the

first

channel

to

complete

the

selection

sequence.

Once

the

2841

is

selected

by

a

channel,

it

remains

selec-

ted

to

that

channel

until

an

end

status

exists.

The

channel

selection

switch

then

returns

to

neutral

un-

less

one of

the

following

conditions

exists.

1.

The channel

indicates

command

chaining.

2.

The

last

status

byte

is

associated

with a

·channel-initiated

signal

sequence,

it

is

stacked

by

the

channel.

3.

The

last

status

byte

contains

the

unit

check

bit.

4.

No

command

other

than

an

I/O

or

a No-op

has

been

initiated

since

the

last

unit

check

condition

occurred.

27

If

Channel A (B)

attempts

to

select

the

2841

while

the

2841

is

selected

to

Channel B (A),

the

2841

responds

to

Channel A (B) with

control

unit

busy.

This,

in

turn,

causes

the

2841 to

attempt

to

present

to

Channel A (B) a

status

byte

containing

control

unit

end

after

the

channel

selection

switch

returns

to

the

neutral

position.

The

address

byte

associated

with

this

status

condition

is

the

base

address

of

the

2841

on

that

channel.

This

control

unit

busy

condition

may

occur

on

any

attempt

to

select

the

2841,

including

initial

program

load,

Test

I/O,

etc.

Device

Reservation

(See

Device

Reserve

and

Device

Release

Commands)

When a

device

is

reserved

to

Channel A (B),

any

command

from

Cha~mel

B (A)

addressed

to

that

device

is

rejected

with

a

busy

indication

in

the

initial

status

byte.

This,

in

turn,

causes

the

2841

to

attempt

to

present

to

Channel

B (A) a

status

byte

containing

Device

End

after

the

reservation

has

been

terminated.

The

address

byte

associated

with

this

status

byte

is

the

same

as

that

associated

with

the

Busy

status

byte.

Device

End

status

resulting

from

the

completion

of a 'Seek

command

is

presented

to

the

channel

that

issued

the

command.

A

device

that

generates

Device End

status

when

it

changes

from

the

not-ready

to

the

ready

state

causes

the

2841

to

present

this

type of

Device

End

status

to

both

channels.

However,

no

attempt

is

made

to

present

such

status

on one

channel

while

the

device

is

reserved

to

the

other

channel.

A

reset

can

be

initiated

by

either

channel

at

any

time.

A

reset

causes

all

reservations

and

status

conditions

stored

in

the

2841

and

the

re-

setting

channel

to

be

reset

in

the

2841.

Reservations

and

status

conditions

the

other

channel

are

not

affected.

Addressing

The

base

address

(four

high-order

bits)

of

the

2841

on

one

channel

is

independent

of

the

base

address

of

the

2841

on

the

other

channel.

However,

the

four

low-order

address

bits

for

any

attached

device

must

be

the

same

on

both

channels.

Usage

Meter

A

single

usage

meter

records

process

time

in

the

2841;

however,

a

separate

Enable

switch

is

provided

for

each

channel.

28

Power

Control

A

power

control

interface

is

provided

for

each

channel.

If

either

channel

indicates

power

"ON"

the

2841

turns

on.

The 2841

turns

off

only

if

both

chan-

nels

indicate

power

"OFF".

If

the

Emergency

Power

OFF

switch

of

either

channel

is

activated,

the

2841

power

is

turned

off.

Record

Overflow

(Special

Feature)

The

Record

Overflow

feature

is

provided

to

allow a

logical

record

to

overflow

from

one

track

to

another.

It

is

useful

in

achieving

a

greater

data

packing

efficiency

and

in

formatting

records

which

exceed

the

capacity

of

a

track.

The

cylinder

boundary

is

the

limiting

factor

to

the

size

of a

record.

Formatting

OVerflow

Records

A

portion

of

an

overflow

record

which

is

written

on

one

track

is

called

a

record

segment.

Each

record

segment

is

processed

as

a

normal

record

during

Format

Write

operations.

The

Write

Special

Count,

Key,

and

Data

CCW

is

the

command

used

for

for-

matting

all

segments

of

an

overflow

record

except

the

last

segment.

The

last

segment

is

written

by

the

normal

Write

Count,

Key,

and

Data

CCW.

The

Write

Special

CCW

causes

a

bit

to

be

writ-

ten

in

Flag

byte

one

in

bit

position

one

of

the

record

segment

being

written.

Otherwise,

the

Write

Special

CCW

functions

just

like

the

normal

Write

command.

All

overflow

segments

must

be

recorded

as

the

first

record

following

RO

on

the

overflow

track.

Overflow

segments

are

normally

recorded

with-

out

a Key

Field,

since

only

the

Key

Field

of

the

first

segment

has

significance.

All

overflow

record

seg-

ments,

except

the

last

one,

are

full

track

records.

Processing

OVerflow

Records

The

following CCWs

operate

on

an

overflow

record

as

though

it

were

a

normal

record

if

the

Overflow

Record

feature

is

installed:

Read

Data

Read

Key

and

Data

Read

Count-Key

and

Data

Write

Data

Write

Key

and

Data

The

2841

detects

that

flag

byte

bit

position

one

is

a

1-bit.

After

completing

the

read

or

write--

operation

on the

first

segment

based

on

the

count

of

the

first

segment,

the 2841

searches

for

the

Index

Point.

At

Index

Point,

the

Head

is

selected

and the 2841

searches

for

the

first

Address

Marker

on the

track.

Then,

under

control

of

the

Data

Length in the Count

Area,

it

processes

the

Data

Field

of

this

record

segment.

This

opera-

tion

continues until the 2841

detects

a

record

seg-

ment

which contains a

zero

bit

in

flag

byte

bit

position

one.

At

the

end of

this

record

segment,

the

operation

is

terminated.

A

CCW

chain

which

starts

operation

on a

re-

cord

segment

other

than

the

first

segment

is

proc-

essed

as

though

it

started

on

the

first

segment.

This

type

of

operation

may

make

it

desirable

to

repeat

the

Key

Field

in

all

record

segments

if

the

chain

of CCWs

is

dependent on a

Search

Key Equal.

Search

ID,

Search

Key, and

Read

Count CCWs

operate

on

each

record

segment

as

though

each

were

a

normal

record.

Unusual Conditions. In addition to

the

checks

pro-

vided

in

normal

processing

of any

record,

certain

conditions

can

occur

which

are

unique to overflow

records.

The commands

stop

immediately

on

de-

tecting

the following conditions:

1. Overflow to a Defective

Track

Overflow Incomplete and

Track

Condition

Check

sense

bits

will

be

set

if

an overflow

occurs

to a

track

which

has

been

flagged

as

defective.

2. Overflow

From

an

Alternate

Track

Overflow Incomplete and

Track

Condition

Check

sense

bits

are

set

if

an

attempt

is

made

to overflow

from

a

track

flagged

as

an

alternate.

3. Overflow Violating a

File

Mask

Attempting

to

overflow by

issuing

a

com-

mand

in

violation

of

a file

mask

sets

Over-

flow

Incomplete,

File

Protected,

and

Command

Reject

(write

command

only)

sense

bits.

4.

Overflow

to

a

Track

with

Incorrect

Head

Number

Overflow

Incomplete

and Seek Check

sense

bits

are

set

if

the

Head

number

compare

is

unequal

during

an

overflow.

This

condition

occurs

if

the

last

Seek

Address

issued

to

the 2841

is

not

the

address

of the

track

with

the overflow

record

and

an

overflow

record

is

being

read

or

written.

28.1

Introduction

The

IBM

System/360

is

used

in

many

applications

which

require

that

files

of

medium

size

be

accessible

to

the

central

processor.

These

files

may

contain

customer

account

balances,

current

inventory

status,

payroll

information,

computer

operating

programs,

or

other

information,

permanent

or

temporary,

to

which

the

central

processor'

must

refer

to

complete

the

specific

application.

If

all

files

need

not

be

directly

accessible

(on

line)

to

the

central

processor

at

all

times,

operating

and

equipment

economies

can

be

realized

if

the

file

can

be

separated

from

the

file

drive.

As

with

mag-

netic

tape,

an

unlimited

volume

of

data

can

be

stored

away

from

the

central

processor

(off-line).

Appro-

priate

data

files

can

be

placed

on-line

as

required

by

the

processing

schedule.

It

may

also

be

desirable

to

be

able

to

transfer

data

files

from

one

file

drive

to

another

(possibly

attached

to

a

second

central

processor).

This

allows

one

system

to

process

and

update

a

data

file,

and

another

(possibly

a

smaller

satellite

system),

to

print

reports

or

answer

inquiries.

This

capability

also

enables

a

second

system

to

complete

a

task

if

the

primary

system

is

not

available

because

of

other

appl

ications.

The

IBM 2311

Disk

Storage

Drive,

with

IBM 1316

Disk

Packs,

offers

processing

features

which

answer

the

needs

of

many

data

processing

applications:

Storage

capacity:

High

speed

accessibility:

Data

file

removability:

Fast

data

transfer

to

the

processor.

Multiple

unit

growth

potential:

Over

7. 2

million

bytes

per

disk

pack

85

milliseconds,

average

Disk

pack

change

time:

about

one

minute

156,000

bytes

per

second

Up

to

eight

2311's

58

million

bytes,

on

a

single

2841

control

unit

IBM 2311 DISK STORAGE

Compatibility

between

units:

Large

volume

of

data

available

at

a

single

access:

Device

Description

1316'

s

compatible

between

any

2311

's

used

on

IBM

System/360

Over

36,

000

bytes

per

cylinder

The

IBM 2311

Disk

Storage

consists

of two

main

com-

ponents:

the

2311

Disk

Storage

Drive

and

the

1316

Disk

Pack.

Storage

Medium

(1316

Disk

Pack)

Each

disk

pack

consists

of

six

14-inch

disks,

mounted

1/2

inch

apart

on a

central

hub.

Data

is

recorded

on

the

inside

ten

disk

surfaces.

The

two

outer

surfaces

are

covered

by

protective

plates.

The

entire

assembly

of

disks,

hub,

and

protective

plates

is

rotated

at

2,400

revolutions

per

minute

(25

ms

per

revolution).

Each

disk

pack

weighs

about

ten

pounds.

The

two-piece

plastic

cover

is

designed

to

protect

disks

against

damage.

A

built-in

handle

on

the

top

cover

makes

carrying

easy

and

efficient.

A

self-

locking

device

in

the

handle

permits

removal

of

the

top

cover

only

when

the

pack

is

mounted

on

the

disk

storage

drive.

Access

Mechanism

When

the

1316

Disk

Pack

is

mounted

in

the

2311

Disk

Storage

Drive,

information

is

written

on

and

read

from

the

ten

disk

surfaces

by

magnetic

read/write

heads.

These

read/write

heads

are

mounted

in

pairs

between

each

two

disks

on

a

movable

comb-like

access

mechanism.

When

in

operation,

the

read/write

heads

float

over

the

disk

surfaces

on a

thin

film

of

air.

Access

Time

Cylinder-to-cylinder

(horizontal)

access

time

varies

according

to

the

number

of

cylinders

traversed.

Ac-

cess

time

from

a

cylinder

to

an

adjacent

cylinder

is

30

ms.

Maximum

access

time

(from

cylinder

202

to

cylinder

000)

is

145

ms,

and

the

average

time

for

"random"

accesses

is

approximately

85

ms

(Figure

13)

29

~~

~

~~

~

140

120

tOO

/

........

~

Vl

80

~

Z

60

40

20

o

~

r

~

/

~

:(

~

, , , , , , , I

~

I I ,

o

20

40

60

Figure 13. Access

Times

...----203

Cylinders

Cylinder Concept

30

80

I I I I I I I I I , I , I I I I I I

tOO

120

140

160

180

200

NO.

TRACKS

TRAVELLED

Once

the

access

mechanism

has

reached

a

cylinder

position,

additional

time

is

required

for

disk

rotation

to

the

desired

record.

At

2,400

revolutions

per

min-

ute,

rotation

time

is

25

ms,

and

one-half

revolution

(12.5

ms)

is

the

average

rotational

delay.

Because

the

access

mechanism

includes

one

read/write

head

for

each

disk

surface,

no

vertical

access

motion

is

required.

Figure

13

shows

the

approximate

times

for

access

mechanism

movement

in

either

direction,

excluding

rotational

delay.

This

may

be

used

as

an

aid

in

pro-

gramming

for

the

most

efficient

utilization

of

the

storage

unit.

Data

Record

Addressing

As

the

access

mechanism

is

moved

horizontally,

it

may

be

stopped

at

any

of

the

203

positions.

This

provides

203

data

tracks

on

each

surface.

Since

all

ten

read/write

heads

are

moved

by

a

single

access

mechanism,

a

cylinder

of

ten

data

tracks

is

available

at

each

access

mechanism

position.

Data

Storage

Format

Data

is

stored

in

the

IBM 2311

Disk

Storage

Drive

in

the

format

defined

by

the

IBM 2841

Storage

Control

Unit.

This

format

is

uniform

for

all

storage

devices

attached

to

the

2841.

Capacity

If

IBM

Programming

Systems

are

not

used,

the

first

record

on

each

track

(RO)

may

contain

application

data.

Based

on 200

tracks,

with

all

records

used

for

application

data,

a

single

IBM 1316

Disk

Pack

can

contain

over

7.3

million

bytes,

or

over

14.7

million

packed

decimal

digits.

IBM

Programming

Systems

reserve

the

use

of

the

first

record

on

each

track

(Record

RO)

to

store

various

information

about

the

track.

This

informa-

tion

is

used

by

the

Programming

System,

and

no

application

data

is

included.

Using

this

format,

based

on 200

tracks,

each

1316

disk

pack

can

contain

over

7.2

million

bytes,

or

over

14.4

million

packed

decimal

digits

(Figure

14).

Record

R1

is

the

first

application

data

record,

and

if

R1

is

the

only

data

record

on

the

track,

it

may

contain

up

to

3625

bytes

of

information.

With

the

high

density

recording

techniques

used

in

the

2311,

minute

contamination

particles

can

affect

data

reading

and

writing

and

may

cause

loss

of

bits.

Therefore,

203

tracks

per

disk

surface

are

provided

to

ensure

that

the

stated

capacity,

based

on

200

tracks,

is

maintained

for

the

life

of

the

disk

pack.

Because

each

data

record

has

non-data

compo-

nents,

like

Count

Area

and

Gaps,

track

capacity

for

data

storage

will

vary

with

record

design.

As

the

number

of

separate

records

on a

track

increases,

additional

byte

positions

are

used

by

gaps

so

that

data

capacity

is

reduced.

The

track

capacity

formulas

(Figure

14)

provide

the

means

to

determine

total

byte

requirements

for

records

of

various

sizes

on a

track.

Operator

Controls

and

Indicators

Start/Stop

Key.

This

key

is

lighted

(on)

when

it

is

in

the

Start

position.

With

the

2311

properly

connected

in

a

processing

system,

press

this

key

to

the

Start

position

to

supply

power

to

the

disk

drive

motor

and

other

2311

com-

ponents.

When

the

disk

drive

motor

has

come

to

speed,

and

other

components

are

ready

for

operation,

the

read/write

heads

are

moved

into

position

and

the

access

mechanism

performs

an

automatic

seek

cycle.

Pressing

the

Start/Stop

key

when

it

is

in

the

Start

position

changes

it

to

the

Stop

position.

This

action

causes

the

access

mechanism

to

retract

from

the

disk

Index Home

~~'-----Record

RO

"I~

Record R1,

R2,

---R(n_l)

~1:4

Record

Rn

------

..

~I

~~~~;

Point Address

~

D B B

"""1

-Data

......

1

BB

B

r--I

Da ..........

ta

1GB

~

I

Data

I

~

Storage Track

Capacity

Basis in Bytes, Basic Track

Capacity

Bytes Requ i red by

Data

Records

When

RO

is

Used as

Specified

When

RO

is

Used for

Data

Records

(except

for last record)

Last

Record

Units

By

IBM

Programming Systems. Dato Without Key With Key Without Key With Key

2311

3625 3694

61+1.049D

L

81

+

1.049(K

L + DL

)

DL

20+(K

L + DL

}

Record

RO

used as

specified

by Number

of

Equa I Length Records Per 2311 Track

IBM

Programming Systems. No

application

data;KL

=

0;

DL

0=

8 1 2 3 4 5 6 7 8 9 10

11

12 13 14 15 16 17 18 19 20

Without Key 3625 1739 1130 829 650

531

446

383 334 294 262 235 212 193 176

161

148 137 127 117

With Key 3605 1719 1110 809 630

511

426

363 314 274 242 215 192 173 156

141

128 117 107 97

Figure

14.

2311

Capacity

31

pack

and

removes

power

from

the

disk

drive

motor.

Automatic

braking

stops

disk

pack

rotation

in

a few

seconds.

Select

Lock

Indicator.

When on,

this

indicates

a

machine

condition

which

requires

Customer

Engineer-

ing

attention.

This

condition

causes

the

disk

storage

drive

to

be

disabled

and

stops

the

usage

meter.

Enable/Disable

Switch. When

the

CPU

is

in

the

stopped

state,

this

switch

enables

or

disables

the

communication

of

the

storage

drive

with

the

CPU.

It

also

enables

or

disables

the

equipment

usage

meter.

If

the

CPU

is

running

when

the

switch

setting

is

changed,

the

storage

drive

and

usage

meter

operating

status

are

not

changed

until

the

CPU

is

placed

in

the

stopped

state.

(See

also

Select

Lock

Indicator.

)

Operating

Procedures

Disk

Pack

Handling

Each

disk

pack

is

protected

in

transit

by

special

carton

inserts

and

special

protective

material.

When

received,

examine

the

carton

closely.

If

its

condition

is

acceptable,

remove

the

disk

pack

and

store

it.

Keep

the

carton

and

inserts;

you

may

need

them

later.

If

the

carton

or

its

contents

show any

unusual

shipping

damage,

do

not

use

the

disk

pack.

Retain

the

damaged

carton

and

disk

pack

in

its

"as

received"

condition

and

notify

your

IBM

Customer

Engineer

immediately.

Disk

packs

have

been

designed

for

ease

of

trans-

port

from

location

to

location.

For

best

shipping

results:

1.

Be

sure

the

pack

is

secure

in

its

two-piece

cover.

2.

Use

only

the

specially

designed

IBM

shipping

carton

with

its

special

protective

padding

properly

inserted.

If

the

original

carton

is

worn

or

damaged,

a

new

carton

may

be

ordered

from

your

local

IBM

office.

Handle

a

disk

pack

only

with

its

cover

on.

If

the

disk

pack

is

accidentally

dropped,

or

receives

a

sharp

impact

of

any

kind,

call

an

IBM

Customer

Engineer

before

using

it.

Disk

Pack

Labeling.

For

positive

identification,

small

adhesive-backed

labels

can

be

placed

on

the

disk

pack

center

hub.

Labels

in

this

location

can

be

read

through

the

transparent

disk

pack

cover.

32

The

following

operating

procedures

should

be

followed

when

labeling

disk

packs:

1.

Use

adhesive-backed

labels

which

can

be

applied

and

removed

easily.

2.

Use

a

writing

implement,

like

a

pen

or

felt-

tip

marker,

which

does

not

produce

loose

residue.

Do

not

use

a

lead

pencil.

3.

Write

on

the

label

before

it

is

applied

to

the

disk

pack.

4.

Place

the

label

only

on

the

center

hub,

not

on

the

disk

pack

cover

or

top

disk

surface.

5.

Use

a new

label

if

changes

are

necessary.

N

ever

use

an

eraser

because

microscopic

eraser

particles

can

damage

disk

surfaces

and

read/write

heads.

Disk

Pack

Loading

and

Unloading.

The

following

procedures

should

be

followed

for

rapid,

effective

disk

pack

changing:

Loading.

1. Open

the

2311

cover.

2.

Remove

the

bottom

disk

pack

cover

by

turn-

ing

the

bottom

locking

knob.

3.

Place

the

1316

disk

pack

(still

contained

in

top

cover)

on

the

2311

spindle.

4.

Turn

the

top

cover

in

direction

of

ON

arrow

until

firm

resistance

is

met.

5.

Lift

the

top

cover

from

the

disk

pack.

6.

Close

the

2311

cover.

7.

Press

the

2311

Start

key.

8.

Reassemble

the

top

and

bottom

covers

of

the

disk

pack.

9.

Store

the

covers

in

a

clean

cabinet

or

on

a

clean

shelf.

I

CAUTION: Do

not

leave

disk

pack

top

cover

inside

Disk

Drive.

Unloading.

1.

Press

the

2311 Stop

key.

2.

Wait

for

the

disk

pack

to

stop

rotating.

3.

Separate

the

top

and

bottom

disk

pack

covers.

4.

Open

the

2311

cover.

5.

Place

the

disk

pack

top

cover

over

disk

pack.

6.

Turn

the

top

cover

in

direction

of

OFF

arrow

at

least

two

full

turns.

7.

Lift

the

top

cover,

now

containing

the

disk

pack,

from

the

spindle.

8.

Fasten

the

bottom

cover

to

disk

pack

(firmly).

9.

Close

the

2311

cover.

10.

Store

the

disk

pack

in

a

clean

cabinet

or

on a

clean

shelf.

Disk

Pack

Storage.

To

assure

maximum

disk

pack

life

and

reliability:

1.

Store

the

disk

packs

flat,

not

on

edge.

2.

Each

pack

should

rest

on a

shelf,

not on

another

disk

pack.

3.

Store

in

a

clean,

enclosed

metal

cabinet

or

a

similar

fire-resistant

container;

never

in

direct

sunlight.

4.

Store

disk

packs

in

a

machine-room

atmos-

phere

(600

to

900

F,

10%

to

80%

humidity).

5.

If

disk

packs

must

be

stored

in

a

different

environment,

allow

two

hours

for

adjust-

ment

to

machine

room

atmosphere

before

use.

33

IBM 2302 DISK STORAGE, MODELS 3

AND

4

Introduction

The

IBM 2302

provides

the

using

system

with:

• High

data

storage

capacity

•

Fast,

direct

access

to

stored

data

• High

data

transfer

rate

•

Flexible

data

organization

The

IBM 2302

Disk

Storage

provides

fast

access

to

vast

quantities

of

on-line,

stored

information.

Random

access

to

specific

areas

of

information

enables

the

user

to

locate

any

data

record

within

a

maximum

of 180

milliseconds,

without

sequential

address

searching.

Thus,

voluminous

master

record

files

may

be

stored

on-line

ready

for

immediate

ref-

erence

or

updating.

Maintenance

of

master

record

files

is

immediate

and

direct;

the

most

current

information

available

is

entered

into

the

proper

area

of

the

master

record

file

as

transactions

occur.

Complex

accounting

pro-

cedures

can

be

simplified,

because

intermediate

man-

ual

operations,

necessary

to

maintain

off-line

record

files,

are

eliminated.

Device

Description

storage

Medium

Disk

storage

consists

of

thin

metal

disks

uniformly

coated

with

a

magnetic

recording

medium.

Data

and

control

information

are

r~corded

as

magnetized

spots

on

the

coated

surfaces

of

the

disks

in

concentric

data

tracks.

Access

Mechanism

Horizontal

positioning

of

the

read/write

heads

is

per-

formed

by

a

hydraulic

access

mechanism

containing

46

data

read/write

heads.

During

a

seek

operation,

the

access

mechanism

positions

the

read/write

heads

at

the

program

specified

track

location.

No

vertical

movement

is

necessary

because

there

is

a

head

for

each

data

surface.

It

is

not

necessary

to

perform

an

additional

seek

operation

if

the

desired

record

is

in

the

same

vertical

plane

(cylinder)

as

the

only

electronic

head

selection

is

necessary.

34

Two

access

mechanisms

are

used

to

address

the

500

data

tracks

on

the

disk

surface.

One

access

mechanism

services

the

inner

250

data

tracks,

and

the

other

access

mechanism

services

the

outer

250

data

tracks

(Figure

15).

The

two

access

mechanisms

of

the

2302

are

addressed

as

Access

0

for

the

outer

250

cylinders

and

Access

1

for

the

inner

250

cylinders.

The

two

access

mechanisms

on

the

2302

operate

independently

and

may

be

in

motion

simultaneously.

Each

mechanism

is

restricted

to

motion

within

its

own

zone of

operation;

accordingly,

one

access

mech-

anism

cannot

read

a

track

written

by

the

other

access

mechanism.

Access

Group.

The

access

mechanism,

together

with

the

attached

read/write

heads,

and

the

250

tracks

serviced

by

it,

comprise

an

access

group.

Two

access

groups

are

provided

with

the

2302 Model

3,

and

four

are

provided

with

the

2302 Model

4.

Disk

Storage

Module.

A

stack

of

25

magnetic

disks

(50

disk

surfaces)

together

with

the

associated

read/

write

heads

and

the

horizontal

positioning

mechanisms

comprise

a

disk

storage

module.

Model 3

and

Model

4

Disk

Storage

Designation.

Model

(3

or

4)

designation

refers

to

the

number

of

disk

storage

modules

provided.

Model 3

disk

storage

con-

tains

one

module

of

disk

storage;

Model 4

contains

two

modules

of

disk

storage,

one

above

the

other.

500

Data

Tracks

per

Disk;

Two

Access Mechanisms

per

Module.

Figure

15.

Access

Mechanisms

TO

Cylinder

Address

0- 0- 0- 0-

0- 0-

0-

~

0- 0- 0-

~

0-

8 N M

~

8

-0

ex)

~

0 N

0 0 0 0 0 0

~

;!

!!?

I .I I I I I I I I

'I

I I I I I I

§ 0 0 0 0 0 0 R 0 0

~

0 0

~

0

;:;

N 8

C!

8 8

~

::I

~

-8

.=

>.

u

~

140-1

~

150-1

u..

160-

170-1

0 0

NOTE:

These

times

do

not include rotational-delay time.

Figure

16.

2302 Disk

Storage

Access

Time

Access

Time

Access

to

one

specific

track

on a

given

recording

surface

is

accomplished

by

the

lateral

movement

of

the

whole

access

mechanism

from

a

current

track

location.

The

time

required

for

this

movement

is

called

access

motion

time

and

is

the

lat-

eral

distance

the

arm

moves.

Figure

16

shows

the

time

requirements

for

access

motion

time

for

the

IBM 2302 Disk

Storage.

!!?

In

addition

to

access

motion

time,

an additional

timing

factor

known

as

rotational

delay

time

is

en-

countered.

Rotational

delay

time

is

the

time

required

for

the

disk

to

position

the

desired

record

at

the

selected

read/write

head.

Maximum

rotation

at

delay

time

is

34

milliseconds;

average

rotational

delay

time

is

17

milliseconds.

$

I

~

0-

ex)

I I

R 0

~

I

0

~

II

~

100ll'iI

.•.•..•.•..

'

.•.•.•.•.

'

.•...•.•.•..•.

'

....•.

~

50

milliseconds

120 milliseconds

180 milliseconds

The

selection

of

the

proper

read/write

head

is

performed

simultaneously

with

access

motion

time.

The

read/write

head

selection

time

consists

solely

of

electronic

switching and

is

negligible.

Total

data

access

time

includes

the

summation

of

access

motion

time

and

rotational

delay

time.

Aver-

age

rotational

delay

time

(17

milliseconds)

is

generally

used

in

this

calculation.

Data

Record

Addressing

The

data

tracks

of

the

cylinders

are

numbered

sequen-

tially

from

bottom

to

top

and

from

outermost

cylinder

to

the

innermost

cylinder

of

each

access

group.

Data

track

numbers

begin

with 0000

at

the

outermost

cylin-

der

of

the

lowest

data

disk

surface,

and

continue up

through

this

outermost

cylinder

to

track

number

0045.

35

Numbering

continues

with

the

lowest

data

track

of

the

cylinder,

0046

and

proceeds

upward

within

the

cylinder.

Continuing

through

each

of

the

cylinders

of

the

single

access

group

in

like

manner,

the

last

track

is

the

top

track

of

the

innermost

cylinder.

Data

Storage

Format

The

format

of

the

data

stored

on

the

2302

is

deter-

mined

by

the

2841

Storage

Control.

It

is

identical

for

all

storage

devices

which

attach

to

the

2841.

Capacity

If

IBM

Programming

Systems

are

not

used,

the

first

record

on

each

track

(RO)

may

contain

application

data.

Based

on

the

use

of

all

record

areas

for

appli-

cation

data,

a

single

IBM 2302

Disk

Storage

Drive

Model 3

can

contain

over

113

million

bytes

or

226

million

packed

decimal

digits

j

the

Model 4

can

contain

over

226

million

bytes

or

452

million

packed

decimal

digits.

/'

IBM

Programming

Systems

reserve

the

use

of

the

first

record

on

each

track

(Record

RO)

to

store

various

information

about

the

track.

This

informa-

tion

is

used

by

the

programming

system,

and

no

application

data

is

included.

By

using

this

format,

each

2302

Disk

Storage

module

can

contain

over

112

million

bytes,

or

over

224

million

packed

decimal

digits.

Record

R 1

is

the

first

application

data

record

and

if

it

is

the

only

data

record

on

the

track,

it

may

contain

up

to

4984

bytes

of

information.

With

the

high

density

recording

techniques

used

in

the

2302,

surface

defects

or

contamination

can

affect

data

reading

and

writing

and

require

that

alter-

nate

tracks

be

used.

Therefore,

rated

capacity

is

112.0

million

bytes

per

module

to

ensure

that

the

stated

capacity

is

maintained.

Because

each

data

record

has

non;"data

components,

such

as

Count

Area

and

Gaps,

the

track

capacity

fqr

data

storage

will

vary

with

record

design.

As

the

number

of

separate

records

on a

track

increases,

additional

byte

positions

are

used

by

gaps

so

that

data

capacity

is

reduced.

The

track

capacity

formulas

(Figure

17)

provide

the

means

to

determine

total

byte

requirements

for

records

of

various

sizes

on a

track.

Indicators

File

Ready

File

Ready

indicates

that

the

2302

has

power

on,

is

up

to

operating

temperature,

and

is

ready

to

accept

or

retrieve

data,

on

demand

of

the

2841

Storage

Con-

trol.

This

light

is

used

to

determine

when

the

stor-

age

device

is

ready

after

power

is

turned

on.

The

light

remains

on

until

power

is

dropped

though

temperature

may

fall

below

normal

operating

range.

Index

Home

I.

I I d I Index

Point Address

toI_.----Record

RO

• • Record RII

R21

---R(n-J)

...

Recor

Rn

-----I

..

~

Point

~

0 I Count I B

I-~-ata-I

B I Count I B

I-D-ata-,

~

ICount I GJ I Data I

~

Storage Track

Capacity

Basis

in

Bytes,

Basic

Track

Capacity

Bytes Required

By

Data Records

When

RO

is

Used

as

Specified

When

RO

is

Used for Data Records (except for last record)

Last

Record

Unit

By

IBM

Programming Systems. Data Without Key With Key Without Key With Key

2302 4984 5053

61

+

1.049

DL

81

+

1.049(K

L

+ DL

)

DL

20+(K

L

+ DL

)

Record

RO

used as specified by Number of Equal length Records Per 2302 Track

IBM

Programming Systems. No

application data;KL

=

0;

Dl

= 8 I 2 3 4 5 6 7 8 9

10

II

12

13 14

15

16 17 18 19 20

Without Key 4984 2402 1569 1157 912 749 632 546 478 424 380 343 312 285

263

243 224 208 195 182

With Key 4964 2383 1550 1138 892 729 613 526 459 405

361

324 293: 266 244 224 205 189 176 163

Figure

17.

2302

Capacity

36

Introduction

Many

data

processing

applications

include

the

main-

tenance

of

very

large

files

of

operating

information.

Direct

access

to

a

large

file

enables

the

central

processor

to

answer

inquiries

about

any

item

in

the

file.

For

processing

economy,

transactions

may

still

be

batched

and

sequenced.

However,

processing

may

be

interrupted,

an

inquiry

about

another

part

of

the

file

answered,

and

processing

resumed

on

an

"up-to-the-minute"

basis.

Thus,

business

decisions

can

be

based

on

the

most

current

data

available,

and

applications

not

previously

practical

can

be

accom-

plished

by

data

processing

equipment.

The

IBM 2321

Data

Cell

Drive

includes

process-

ing

capabilities

which

expand

the

sphere

of

data

processing

applications:

Large

storage

capacity:

Over

418

million

bytes

per

2321

Medium

speed

accessibility:

600

milliseconds

maximum

to

any

record

Data

file

removability:

Data

Cell

change

time:

about

one

minute

Fast

data

transfer

to

the

central

processor:

Compatibility

between

units:

Large

volume

of

data

avail-

able

at

single

access:

Device

Description

55;

000

bytes

per

second

Up

to

eight

2321s

per

2841

Data

.Cells

com-

patible

between

2321s

used

with

IBM

System/360

198, 000

bytes

per

strip

From

a

circular

array

of 10

cells

with

20

sub-

cells

each

(Figure

18), a

rotary

positioning

system

positions

a

selected

subcell

of

ten

strips

beneath

an

access

station.

At

this

station

a

selected

strip

is

first

withdrawn

from

the

subcell,

then

rotated

past

a

read/write

head

element

for

data

transfer,

and

finally

returned

to

its

original

location

in

the

subcell.

IBM 2321 DATA

CELL

DRIVE

Cell

Drive

Data

Cell

positioning

is

initiated

by

a Seek

instruction.

The

cell

drive

rotates

the

circular

array

of

ten

Data

Cells

to one of 200

discrete

subcell

positions.

The

array

can

rotate

in

either

direction

and

always

moves

in

the

direction

that

requires

least

travel.

When

the

array

has

placed

the

subcell

containing

the

addressed

strip

beneath

the

access

station,

a

position

check

is

made

by

a

subcell

position

detector,

which

signals

the

2841

Storage

Control

Unit

that

a

subcell

is

within

the

range

of

the

access

station.

Access

Station

The

addressed

strip

is

exposed

by

parting

the

adjacent

strips

with

separation

fingers.

The

strip

is

selected

from

a

subcell

of 10

and

placed

on a

revolving

drum.

It

is

then

rotated

past

the

read/write

head

block

for

data

transfer.

When

reading

and/or

writing

is

com-

plete,

the

strip

is

returned

to

its

original

subcell

location

by

a

restore

function.

The

read/write

head

block

contains

20

magnetic

elements.

It

can

be

positioned

to

any

of

five

positions

(cylinders),

thus

providing

100

recording

tracks

per

strip.

The

head

block

position

is

specified

by

the

address

in

the

Seek

instruction.

Access

Time

Access

time

is

defined

as

the

length

of

time

required

to

place

a

selected

strip

in

a

data

transfer

position.

Average

access

time

under

varying

conditions

is

listed

in

Figure

19.

Data

Record

Addressing

The

physical

location

of

an

individual

recording

track

is

determined

by

considering

the

following

areas:

Data

Cell

Drive

Data

Cell

Subcell

Strip

Cylinder

Read/Write

Head

Element

When a

record

is

addressed,

the

location

of

each

of

the

areas

just

listed

is

compared

against

the

new

37

10

Ce

115

per

Drive

Figure

18.

2321

Drive,

Cell,

Subcell

Conditions

When only Read/

Write element

selection

is

required

When only Read/

Write head

Block

motion

is

required

When

No

Strip

is

on the

Drum

175

ms

When a previously

Addressed Strip

is

375

ms

on the

Drum

.

Figure

19.

2321 Access

Time

38

250

ms

350

ms

450

ms

550

ms

400

ms

600

ms

SUBCELL

10 Strips

per

Subcell

CELL

20

Subcells per Cell

address.

From

this

comparison,

the

necessary

electronic

and

electromechanical

action

required

to

place

the

addressed

record

in

the

data

transfer

posi-

tion

is

determined.

When

the

new

address

is

the

same

as

the

old

address

in

a

specific

area,

no

access

motion

is

required.

For

example,

if

the

only

difference

between

a new

and

old

address

is

the

selection

of

an

adjacent

track

within

the

same

cylinder

position,

the

only

action

would

be

the

electronic

selection

of

the

proper

read/

write

head

element,

providing

the

strip

was

not

restored

in

the

interim.

Data

Storage

Format

Data

is

stored

in

the

IBM 2321

Data

Cell

Drive

in

the

format

defined

by

the

IBM 2841

Storage

Control.

This

format

is

uniform

for

all

devices

attached

to

the

2841.

Capacity

If

IBM

Programming

Systems

are

not

used,

the

first

record

on

each

track

(RO)

may

contain

application

data.

Based

on

the

use

of

all

records

on a

track

for

application

data,

a

single

IBM 2321

Data

Cell

Drive

can

contain

418

million

bytes

or

836

million

packed

decimal

digits.

IBM

Programming

Systems

reserve

the

use

of

the

first

record

of

each

track

(Record

RO)

to

store

various

information

about

the

track.

This

informa-

tion

is

used

by

the

Programming

System,

and

no

application

data

is

included.

By

using

this

format,

each

2321

can

contain

over

400

million

bytes,

or

over

800

million

packed

decimal

digits

(Figure

20).

Record

R1

is

the

first

application

data

record,

and

if

R1

is

the

only

data

record

on

the

track,

it

may

contain

up

to

2000

bytes

of

information.

Because

each

data

record

has

non-data

com-

ponents,

like

Count

Area

and

Gaps,

track

capacity

for

data

storage

will

vary

with

record

design.

As

the

number

of

separate

records

on

a

track

increases,

additional

byte

positions

are

used

by

gaps

so

that

data

capacity

is

reduced.

The

track

capacity

formu-

las

(Figure

20)

provide

the

means

to

determine

total

byte

requirements

for

records

of

various

sizes

on a

track.

Operator

Controls

and

Indicators

The

operator's

console

on

the

Data

Cell

Drive

con-

tains

indicator

lights

and

manual

controls.

The

indicator

lights

provide

the

machine

operator

with

the

following

information.

Ac

Power

On.

Indicates

that

primary

ac

power

is

applied

to

the

IBM 2321.

Drive

Operative.

Indicates

that

the

2321

has

all

power

on

and no

interlock

conditions

exist.

Interlock

con-

ditions,

such

as

an

open

entry

door

or

an

improperly

mounted

data

or

ballast

cell,

render

the

2321

inoperative.

Drive

Ready.

Indicates

that

the

2321

is

ready

to

per-

form

normal

programmed

operations

under

control

of

the

2841.

Thermal.

Indicates

that

a

high

temperature

condition

exists

within

the

2321.

Drive

Select.

Indicates

that

the

storage

control

unit

is

communicating

with

the

2321.

The

manual

keys

and

switch

enable

the

operator

to

control

the

following

functions.

Restart.

This

key

allows

the

restart

of

the

2321

in

the

event

of

certain

inoperative

conditions,

such

as

a

momentary

interrupt

in

power.

Index

Home

,..

I

Point Address

1oI11i----Record

RO

.. ..

Record

Rl

I

R21

---R(n-D

....

Record

Rn

----

__

~-.I

Point

I I

Index

~

0 1 Count I B

"""1

D-ata--'I

B I Count

I@

I

Data

IB~

~I

Data

1/1

Storage Track

Capacity

Basis

in

Bytes, Basic Track

Capacity

Bytes Required

By

Data

Records

When

RO

is

Used as

Specified

When

RO

is

Used for Dota Records (except for last record)

Lost

Record

Unit

By

IBM

Programming Systems. Data Without Key With Key Without Key With Key

2321

2000 2092

84+

1.049

DL

100+

1.

049

(K

L

+

DL

16+(K

L

+ DL

)

Record

RO

used as

specified

by Number

of

Equal Length Records Per 2321 Track

IBM

Programming Systems. No

application

data;KL =

0;

DL

= 8 1 2 3 4 5 6 7 8 9 10

11

12

13

14 15 16 17 18 19 20

. Without Key 2000 935

591

421

320 252 204 168

141

119 100 85

72

61

52

A3

36

29 23 19

With Key 1984 919 575 406 304 237 189 153 125 103

84

70

57

46

37

28 20 14 8

Figure

20.

2321

Capacity

39

Reset.

This

key

allows

the

2321

indicators

to

be

reset

in

the

event

of

an

improper

status

condition.

This

reset

will

not

establish

a

Drive

Operative

status.

DC

On.

Indicates

that

all

dc

power

within

the

2321

is

on.

Operating

Procedures

Data

Cell

Replacement.

To

facilitate

Data

Cell

re-

placement,

four

operator

aids

are

provided.

40

1.

Entry

door

with

interlock:

The

entry

door

permits

access

to

the

Data

Cell

array.

An

interlocking

switch

is

provided

for

operator

safety.

When

the

door

is

open,

no

machine

controlled

motion

can

occur.

2.

Data

Cell

location

indicator:

The

Data

Cell

location

indicator

identifies,

by

number,

the

Data

Cell

located

in

the

replacement

position.

It

also

indicates

the

number

of

the

Data

Cell

positioned

under

the

access

station.

3.

Manual

by-pass

valve:

The

manual

by-pass

valve

allows

an

operator

to

manually

rotate

the

array

to

place

any

desired

Data

Cell

in

the

replacement

position.

The

valve

is

mechanically

interlocked

with

the

access

station

and

is

closed

automatically

with

the

closing

of

the

entry

door.

4.

Data

Cell

mount

interlock:

An

interlock

switch

is

provided

to

prevent

2321

operation

unless

the

switch

is

properly

closed

by

either

a

Data

Cell

or

a

ballast

cell.

The

following

procedure

should

be

followed

when

replacing

Data

Cells.

1.

Check

the

indicator

lights

for

the

following

pattern:

Ac

Power

should

be

on.

Drive

Operative

should

be

on.

Drive

Ready

should

be

on.

Drive

Select

should

be

off.

2. Open

the

entry

door.

The

Drive

Ready

indi-

cator

should

extinguish.

3.

Check

the

Data

Cell

location

indicator

to

determine

the

physical

position

of

the

desired

Data

Cell.

4.

Open

the

manual

by-pass

valve

and

rotate

the

array

(in

either

direction)

to

place

the

de-

sired

Data

Cell

in

the

replacement

position.

5.

Place

a

Data

Cell

cover

on

the

desired

Data

Cell.

This

action

engages

all

mechanical

and

electrical

interlocks

and

allows

the

Data

Cell

to

be

removed

from

the

machine.

NOTE: New

Data

Cells,

replacement

Data

Cells,

or

ballast

cells

must

be

inserted

in

place

of

removed

cells.

When

the

Data

Cell

cover

is

removed

from

a

properly

inserted

cell,

the

mechanical

and

electrical

interlocks

are

disconnected.

6.

Close

the

entry

door.

7.

Check

the

indicator

lights

for

the

following

pattern:

Ac

Power

on

Drive

Operative

on

Drive

Ready

on

Drive

Select

off

Introduction

The IBM 2303

Drum

Storage

provides

on-line

random

acce~s

storage

of

4.006

million

bytes

on a

magnetic

drum.

Two 2303s

may

be

attached

to

each

2841

Storage

Control

Unit

for

a

total

on-line

random

ac-

cess

storage

of

8.012

million

bytes

or

16.024

million

packed

decimal

digits.

The

drum

is

divided

into

800

data

tracks;

each

track

has

a

read/write

head

and

may

contain

up to

5,008

bytes

of

data.

The

maximum

data

transfer

rate

is

312.5

thousand

bytes

per

second.

Device

Description

The 2303

Drum

Storage

consists

of a

vertically

mounted

drum

and

its

associated

electronic

cir-

cuitry.

The

drum,

coated

with a

magnetic

record-

ing

material,

rotates

at

about

3,

500

revolutions

per

minute.

The

surface

of

the

drum

is

divided

into

tracks.

These

addressable

tracks,

extending

around

the

periphery

of

the

drum,

are

used

for

storing

data

as

follows:

800

Standard

Data

Tracks

80

Alternate

Data

Tracks

The

alternate

tracks

are

provided

to

ensure

that

each

recorded

bit

can

be

stored

in

a

magnetically

perfect

medium.

If a

defect

is

encountered

on a

track,

the

entire

track

is

disabled

and one of

the

alternate

tracks

is

substituted.

This

alternate

track

is

given

the

address

of

the

disabled

track.

Each

data

track

has

its

own

read/write

head,

used

for

both

recording

and

retrieving

data.

The

data

read/write

heads

are

fixed

in

position

on 20

vertical

racks

that

surround

the

drum.

Each

rack

contains

40

data

read/write

heads.

Access

Time

Because

of

the

assignment

of

an

individual

read/write

.

head

to

each

data

track,

data

seek

operations,

with

their

associated

access

motion

time

delay,

are

eliminated.

Therefore,

the

access

time

is

composed

of only

the

rotational

time

of

the

drum.

Maximum

rotational

time

17

. 5

ms.

Average

rotational

time

8.6

ms.

IBM 2303 DRUM STORAGE

Data

Record

Addressing

Arrangement

of

read/write

heads

on

vertical

racks

retains

the

cylinder

concept.

Cylinder

operations

with

the

2303 allow

up

to

800

tracks

to

be

written

or

read

with a

single

drum

storage

order.

Data

Storage

Format

Data

is

stored

in

the

IBM 2303

Drum

storage

in

the

format

defined

by

the

2841

Storage

Control.

This

format

is

uniform

for

all

storage

devices

which

attach

to

the

2841.

Capacity

If

IBM

Programming

Systems

are

not

used,

the

first

record

on

each

track

may

contain

application

data.

Based

on

the

use

of

all

records

on a

track

for

application

data,

a

single.IBM

2303

Drum

Storage

Unit

can

contain

over

4.006

million

bytes

or

over

8.012

million

packed

decimal

digits.

IBM

Programming

Systems

reserve

the

use

of

the

first

record

of

each

track

(Record

RO),

to

store

various

information

about

the

track.

This

informa-

tion

is

used

by

the

Programming

System,

and no

application

data

is

included.

By

using

this

format,

each

2303

can

contain

over

3.

913

million

bytes,

or

7.826

million

packed

decimal

digits

(Figure

21).

Record

Rl

is

the

first

application

data

record,

and

if

Rl

is

the

only

data

record

on

the

track,

it

may

contain up

to

4,892

bytes

of

information.

With

the

high

density

recording

techniques

used

in

the

2303

minute

contamination

particles

can

affect

data

reading

and

writing.

Therefore,

80

alternate

tracks

are

provided

to

ensure

that

the

stated

capacity,

based

on 800

tracks

is

maintained.

Because

each

data

record

has

non-data

compo-

nents,

like

Count

Area

and

Gaps,

track

capacity

for

data

storage

will

vary

with

record

design.

As

the

number

of

separate

records

on a

track

increases,

additional

byte

pOSitions

are

used

by

gaps

so

that

data

capacity

is

reduced.

The

track

capacity

formulas

(Figure

21)

provide

the

means

to

determine

total

byte

requirements

for

records

of

various

sizes

on a

track.

41

~~1~t

A~d~~s

...

14

.....

---Record

RO

~

I-

Record R1,

R2,

---R(n-l)

..

1~

Record

Rn

----

.......

..,1

~~~~:

~

0 I Count I B

-I

-Data-,

B I Count

I@

,--Data-,

~

ICount I G I Data I

~

Storage Track

Capacity

Basis

in Bytes, Basic Track

Capacity

Bytes Required

By

Data Records

When

RO

is

Used as Specified When

RO

is

Used for Data Records (except for lost record)

Last

Record

Unit

By

IBM

Programming Systems Data Without Key With Key Without Key With Key

2303 4892 5008 108 +

DL

146 +

(K

L + DL

)

DL

38 +

(K

L + DL

)

Record

RO

used as specified by Number

of

Equal Length Records Per 2303 Track

IBM

Programming Systems. No

application

data;Kl

=

0;

Dl

= 8 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16 17 18 19 20

Without Key 4892 2392 1558 1142 892 725 606

517

447 392 346 308 276 249 225 204 186 169 155 142

With Key 4854 2354 1520 1104 854

687

568 479 409 354 308 270 238

211

187 166

148

131

117 104

Figure

21.

2303

Capacity

42

APPENDIX

A.

2841/2311

PROGRAMMING

EXAMPLE

The following 2311 Programming

example

is

included

to

illustrate

the

use

of

2841

channel

commands

to

perform

operations

on

attached

storage

devices.

The program was assembled

and

simulated with

the

7090/7094

Support

Package

for

System/360.

The

example

is

solely

for

the

purpose

of

illustration,

it

does not

necessarily

reflect

techniques

in

the

use

of

Operating

System/360 Programs.

Two

separate

operations

are

performed. The first

is

the

writing

of Home Addresses

(HA)

and

Track

Descriptor Records

(RO)

on

all

2030

trocks of

the

2311.

Read Back

Check

of

RO

is

performed in

CPU

storage.

The

second

program writes

three

records on

track

number

37,

reads

,them

into a

separate

I/O

area

and

searches for a fourth

record

which

is

not

there.

The first

routine

is

labeled

HAROWT

and

uses

the

Channel

command list WRDKHA. The

three

record

read/write

and

fourth

record

search

is

performed with

the

CCW list WR3REC. A subroutine (EXCP)

is

used

to

start

I/O.

Not

shown is

an

interrupt

handling

subroutine,

a

subroutine

(BZSIO)

that

acts

on

condition

codes 1, 2

and

3

and

DUMP which dumps

CPU

storage

(as a

debugging

aid) in

case

of

errors or

conditions

not

yet programmed. The system

is

in

the

supervisory mode

and

enabled

for interrupts

at

all

times unless

EXCP

has

disabled

or

the

interrupt

subroutine

is

being

used.

EXCP

sets a

bit

equal

to

one

in

DEVTAB

to

indicate

that

the

device

is

being

used,

this

bit

is

cleared

by

the

interrupt

subroutine

when

the

device

end

bit

appears

in

the

channel

status word.

000112

IB

71

000114

58 40

000118

40 70

00011C 40

10

000120

40

10

000124

58

50

000128

IB

66

00012A 40 60

00012E 40 60

000132

40 60

000136

41

00

00013A 58 10

00013E 45

EO

000142

91

01

000146

41 10

00014A 05 17

000150

47

10

000154

81 64

000158

58

50

00015C 87

14

000160

41

00

000164

S8

10

000168

45

EO

00016C

91

01

000170

47 10

000114

45

EO

000178

45

EO

00017C 80 00

000180

50 00

000184

9C

00

000188 47 10

00018C 50 70

000190

41

11

000194

92

01

000198

58 70

00019C 80 00

0001AO 07

FE

C 2CA

C 4F2

C

4FA

C

4FE

C

202

C 4F4

C

4FC

C 500

C

LAE

C 2E6

C

0711

C

3EF

C 040

C 51E

C 016

C 028

C 206

C 016

C

lEE

C 2E6

C

0711

C

3EF

C

06A

C 166

C

2C7

0 048

1 000

C

OAO

C 276

C

2EE

1 000

C 276

C

2C8

C4FE

*

HAROWT

CYLP

HDLP

*

•

*

HARDER

11:

•

*

EXCP

CaNTIN

WRITE

HOME

ADDRESSES

AND

TRACK

DESCRIPTOR

RECORDS

SR

L

STH

L

SR

STH

LA

L

BAL

TM

BC

CLC

BC

BXLE

L

BXLE

R5,R5

R2,C1

RS,BBCCHH+4

R5,FCCHH+4

RS,ROCNT

R3,C9

R4,R4

R4,BBCCHH+6

R4,FCCHH+6

R4,ROCNT+2

SP,WRDKHA

PL,CI01

R,EXCP

CH1DV1,1

1,*-4

ROCMPR(Z4),ROCNT

7,HAROER

R4,RZ,HDLP

R3,C202

RS,R2,CYLP

SET

CYLINDER

REGISTER

TO

0

SET

INCREMENT

TO

1

STORE

CYLINDER

NUMBER

FOR

SEEK

STORE

CYLINDER

NUMBER

FOR

WRITE

STORE

CYLINDER

IN

TRACK

OES

REC

SET

HEAD

LOOP

CO~PARE

TO

9

S&T

HEAD

REGISTER

TO

0

STORE

HEAD

NU~BER

FOR

SEEK

STORE

HEAD

NUMBER

FOR

WRITE

STORE

HEAD

IN

TRACK

DES.

REC.

WRITE

HOME

ADORESS

AND

TRACK

DESCRIPTOR

RECORD

ON

THIS

TRACK

WAIT

FOR

READ

BACK

COMPLETE

READ

BACK

CHECK

INCREMENT

HEAD

AND

RECYCLE

SET

CYLINDER

LOOP

COMPARE

TO

202

INCRE~ENT

CYLINDER

AND

RECYCLE

WRITE

THREE

RECORDS

ON

CYLINDER

3,

TRACK

7

READ

THEM

BACK

AND

LOOK

FOR

A

FOURTH

(NOT

THERE)

LA

SP,WR3REC

L PL,CID1

B'AL

R,

EXCP

TM

CHIDV1,l

BC

1,

*-4

BAL

R,DUMP

BAL

SSM

ST

SIO

BC

ST

LA

MVI

L

SSM

BCR

EJECT

R,DUMP

START

1/0

SUBROUTINE

CISABL

SP,12(0,0)

O(PL)

7,BlS10

R5,REGS

RS,OEVTAB(Pl)

O(RS),l

RS,REGS

ENABLE

15,R

READ

BACK

CHECK

FAILED

DISABLE

SYSTEM

FROM

INTERRUPTS

SP

CONTAINS

CAW

PL

CONTAINS

DEVICE

ADDRESS

TEST

FOR

UNUSUAL

CONDITIONS

DEVICE

STARTED.

SET

BIT

IN

DEVICE

TABLE

CALLER

BAL

R,

EXCP

AND

R

CONTAINS

RETURN

TO

CALLER

43

2A41/2311

PROGRA~MING

EXAMPLE

•

..

• CHANNEl

COfolMANC

WORD

1I

STS

•

..

WR

ITE

HOME

ADDRESSES

AND

DESCRIPTOR

RECORDS

..

0002BO

IF

0003eB

4COO

0001

WRCKHA

ecw

31,HAMASK,X'4C',1

SET

FILE

MASK

000288

01

0005F2

4COO

0006

ccw

01.BBCCHH+2.X'40'.6

SEEK

TRACK

0002eo

19

0005fB

4COO

0005

CCW

25,FCCHH+3,X'40',5

WR

I

TE

HofolE

ADORESS

0002e8

15

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4COO

001S

CCW

21.ROCNT.X'40'.24

IoiR

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TRACK

DESCRIPTCR

RECORD

000200

39

0005FC

4000

0004

CCW

57;FCCHH+4,X'40',4

SEARCH

HA

EOUAl

000208

OS

0002E8

OCOO

OOOQ

CCW

OS,.+16,O,C

O('l02EO

16

000620

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0018

ecw

22,ROCMPR,Q,24

READ

RO

0002ES

03

0002E8

COOO

0000

ccw

03,·,0.0

ERROR

EXIT

•

..

WRITE

AND

REAP

BACK

THREE

RECORPS

..

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IF

0003eB

4COO

0001

WfOREC

CCW

3l.HAMASK.64.1

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FILE

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07

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4COO

0006

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SEEK

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TRK

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08,*-8,0,0

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03

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NQRCH)

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..

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AREA

FOR

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REG

I STERS

..

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REGS

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16F

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00

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§II]

44

2841/2311

PROGRA~MING

EXA~PlE

•

CONSTANTS

•

OOOJBA

0000000000

NICPSW

DC

Xl5'OOOOOOOOOO'

OOOlBD

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DC

Al3{INTl

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DC

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FILE

MASK-ALL

WRITES-All

SEEKS

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00000001

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DC

F

'1'

000100

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DC

F'4'

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C<.l

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F'<.l'

000308

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F'202'

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DC

F'

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TAPE

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00000101

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2311

SYSCKI

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DEVTAA

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STATUS

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DEVICES

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OS

Cll6

KEY

OOOA

71

OS

2CL16

DA

TA

0001\

91

00030007031

C

0200

REC3

OC

X'OO030007031C0200'

COUNT

OOOA

99

09C5C3060QC440F340

DC

CL16'RECORC 3

KEYKEY

•

KEY

00OAA2

02C5E802C5E840

000AA9

OS

32CLl6

DATA

OOOC

AC

RECIKO

OS

260F

BUFFER

FOR

READ

BACK

0010t3C

REC2CC

OS

14F

0010F4

REC3CC

OS

134F

OODOC

0003000704

REC4

DC

X'0003000704'

RECORD

NOT

THERE

YET

~

4S

APPENDIX

B.

HEXADECIMAL-DECIMAL

CONVERSION

The

table

in

this

appendix

provides

for

direct

con-

Hexadecimal

Decimal

version

of

decimal

and

hexadecimal

numbers

in

these

4000

16384

ranges:

5000

20480

6000

24576

Hexadecimal

Decimal

7000

28672

000

to

FFF

0000

to

4095

8000

32768

For

numbers

outside

the

range

of

the

table,

add

9000

36864

AOOO

40960

the

following

values

to

the

table

figures:

BOOO

45056

Hexadecimal

Decimal

COOO

49152

1000

4096

DOOO

53248

2000

8192

EOOO

57344

3000

12288

FOOO

61440

0

r------

1

r------

E r-----

--

9

I I I

r---------------------J I I

Ir------------------------------------J

I

II

r------------'

II

0 2 3 4 5 6 7 8 A B C D E F

0000

0001

0002

0003 0004 0005

0006

0007

0010

0011

0012

0013 0014

0015

0016

0017

0018

0019

0020

0021

0022 0023

0026 0027 0028 0029

0030

0031

0032

0033

0034

0035

0036

0037

003S

0039 0042

0043

0044

0045

0046

0047

0048

0049 0050

0051

0052

0053 0054 0055 0058 0059 0060

0061

0062

0063

04

_

0064

0065 0066

0067

0068

0069

0070

0071

0074

0075 0076 0077

0078

0079

05

_

0080

0081

0082

0083

0084 0085

0086

0087 0090

0091

0092 0093 0094

0095

06_

0096 0097

0098 0099 0100

0101

0102

0103

0106 0107

0108 0109 0110

0111

07

_

0112 0113 0114 0115

0116

0117

0118 0119

0122

0123

0124

0125 0126

0127

08

_

0128

0129 0130

0131

0132 0133 0134

0135

0138

0139 0140

0141

0142 0143

09

_

0144 0145

0146

0147

0148

0149

0150

0151

0154 0155

0156

0157

0158

0159

OA_

0160

0161

0162 0163

0164 0165

0166

0167

0170

0171

0172

0173

0174 0175

OB_

0176

0177

0178 0179

0180

0181

0182 0183 0186

0187

0188 0189 0190

0191

OC_

0192 0193 0194

0195 0196

0197

0198

0199

0202 0203

0204

0205 0206

0207

OD_

0208 0209 0210

0211

0212

0213 0214

0215 0218 0219 0220

0221

0222

0223

OE

_

0224 0225

0226

0227

0228

0229

0230

0231

0234

0235 0236 0237

0238

0239

OF

_

0240

0241

0242

0243

0244

0245

0246 0247

0250

0251

0252

0253

0254

0255

10_

0256 0257 0258

0259 0260

0261

0262 0263 0266

0267

0268

0269 0270

0271

11_

0272 0273

0274

0275

0276

0277

0278

0279 0282 0283

0284

0285 0286

02~7

12

_

0288

0289 0290

0291

0292

0293 0294

0295

0298

0299 0300

0301

0302 0303

13

_

0304 0305

0306 0307 0308

0309

0310

0311

0314 0315

0316 0317 0318 0319

14

_

0320

0321

0322 0323

0324

0325 0326

0327

0330

0331

0332 0333

0334

0335

15

_

0336 0337

0338

0339

0340

0341

0342 0343

0346

0347 0348 0349

0350

0351

16

_

0352

0353

0354

0355

03.56

0357

0358 0359

0362

0363

0364

0365 0366

0367

17

_

0368

0369

0370

0371

0372

0373 0374

0375 0378

0379 0380

0381

0382 0383

0384

0385 0387

0388

0389

0390

0391

0394

0395

0396

0397 0398 0399

0400

0401

0403 0404

0405

0406

0407

0410

0411

0412 0413 0414

0415

0416 0417

0419

0420

0421

0422 0423 0426

0427

0428

0429 0430

0431

0432 0433 0435 0436

0437 0438

-

0439

0442

0443

0444

0445

0446 0447

0458

0459 0460

0461

0462 0463

0474

0475 0476

0477 0478 0479

0490

0491

0492

0493

0494

0495

0506

0507 0508

0509

0510

0511

~

46

20£+0:12

1 2 3 4 5 6 7 8 9 A B C D E F

0513 0514 0515

0516 0517 0518 0519

0520

0521

0522

0523

0524 0525 0526

0527

21_

0528 0529 0530

0531

0532

0533

0534

0535 0536 0537

0538 0539 0540

0541

0542

0543

22_

0544 0545

0546 0547

0548

0549 0550

0551

0552

0553

0554

0555 0556 0557

0558 0559

23-

0560

0561

0562 0563

0564

0565

0566 0567

0568

0569

0570

0.571

0572

0573

0574

0575

24

_

0576

0577 0578

0579

0580

0581

0582

0583

0584

0585

0586

0587 0588

0589

0590

0591

25-

0592

0593

0594

0595

0596

0597

0598

0599 0600

0601

0602

0603 0604 0605

0606

0607

26

_

0608

0609

0610

0611

0612

0613

0614

0615 0616

0617

0618

0619 0620

0621

0622

0623

27

_

0624 0625

0626 0627

0628

0629

0630

0631

0632

0633

0634

0635 0636

0637 0638

0639

28

-

0640

0641

0642 0643

0644

0645 0646 0647

0648 0649

0650

0651

0652 0653

0654

065.5

29

-

0656 0657 0658

0659

0660

0661

0662

0663

0664 0665

0666

0667

0668

0669 0670

0671

2A_

0672 0673 0674 0675

0676

0677 0678 0679

0680

0681

0682 0683

0684

0685 0686

0687

2B-

0688 0689 0690

0691

0692

0693 0694

0695

0696

0697

0698

0699 0700

0701

0702

0703

2C-

0704

0705 0706

0707 0708

0709

0710 0711

0712 0713

0714

0715

0716

0717 0718

0719

2D_ 0720

0721

0722

0723

0724

0725 0726 0727 0728 0729

0730

0731

0732 0733

0734

0735

2E_

0736 0737 0738

0739

0740

0741

0742

0743

0744 0745

0746

0747 0748

0749

0750

0751

2F-

0752 0753 0754

0755

0756

0757 0758 0759 0760

0761

0762

0763 0764 0765 0766 0767

30_

0768

0769 0770

0771

0772 0773 0774 0775

0776

0777

0778

0779 0780

0781

0782 0783

31_

0784 0785 0786 0787 0788

0789

0790

0791

0792 0793 0794 0795 0796

0797

0798

0799

32

-0800

0801

0802 0803

0804

0805

0806

0807

0808 0809

0810

0811

0812

0813

0814

0815

33_

0816 0817

0818

0819 0820

0821

0822 0823

0824 0825

0826

0827

0828

0829

0830

0831

34

_

0832 0833 0834 0835 0836 0837 0838 0839 0840

0841

0842

0843 0844

0845 0846 0847

35

-

0848 0849 0850

0851 0852

0853

0854

0855

0856

0857

0858 0859 0860

0861

0862

0863

36

_

0864 0865 0866

0867 0868

0869 0870

0871

0872 0873

0874 0875

0876 0877 0878

0879

37

_ 0880

0881

0882 0883

0884

0885 0886 0887 0888 0889

0890

0891

0892 0893 0894 0895

38

_

0896

0897

0898 0899

0900

0901

0902 0903

0904 0905

0906

0907

0908

0909

0910

0911

39_

0912

0913 0914 0915

0916

0917

0918

0919

0920

0921

0922

0923

0924

0925 0926 0927

3A_ 0928

0929 0930

0931

0932

0933

0934

0935 0936 0937

0938 0939

0940

0941

0942

0943

3B_

0944

0945 0946 0947

0948

0949 0950

0951

0952

0953 0954

0955 0956 0957 0958

0959

3C_

0960

0961

0962 0963

0964

0965

0966

0967

0968

0969 0970

0971

0972

0973

0974

0975

3D-

0976 0977 0978 0979

0980

0981

0982

0983

0984

0985

0986

0987 0988

0989

0990

0991

3E_

0992 0993

0994

0995 0996 0997 0998 0999

1000

1001

1002 1003

1004

1005 1006 1007

3F _

1008 1009

1010

1011

1012

1013

1014 1015

1016 1017

1018

1019 1020

1021

1022

1023

0 1 2 3 4 5 6 7 8 9 A B C D E F

40_

1024

1025 1026

1027

1028 1029

1030

i031

1032 1033 1034 1035 1036 1037

1038

1039

41_

1040

1041

1042

1043

1044 1045 1046 1047

1048 1049

1050

1051

1052

1053

1054

1055

42_

1056 1057 1058 1059

1060

1061

1062 1063

1064

1065 1066 1067

1068

1069

1070

1071

43

_

1072

1073

1074

1075

1076

1077 1078

1079

1080

1081

1082 1083

1084

1085 1086 1087

44_

1088 1089 1090

1091

1092 1093

1094 1095

1096 1097

1098

1099

1100

1101

1102 1103

45_

1104

1105

1106

1107 1108

1109

lll0

llll

ll12 ll13

1114

lll5

1116 1117 1118

ll19

46_

1120

ll21

1122

ll23

ll24

ll25

ll26 ll27

1128

1129 1130

ll31

1132

1133

ll34

ll35

47

_

ll36

1137 1138

1139

1140

1141

ll42 ll43

1144 1145

1146

1147 1148

1149

ll50

1151

48_

1152 1153

ll54

ll55

1156

ll57 ll58

ll59

1160

ll61

ll62 ll63

ll64

ll65

1166 1167

49_

1168

ll69

1170

1171

1172

1173

ll74

1175 1176

1177

ll78

1179 1180

1181

1182

ll83

4A_

1184

ll85 ll86 ll87 ll88 ll89

1190

1191

1192

1193

1194

ll95

1196

ll97 ll98

ll99

4B_

1200

1201

1202 1203 1204

1205

1206 1207

1208

1209

1210

12ll

1212

1213 1214 1215

4C_

1216

1217

1218

1219 1220

1221

1222

1223 1224

1225

1226

1227

1228 1229 1230

1231

4D_

1232

1233

1234

1235

1236

1237

1238 1239 1240

1241

1242

1243 1244

1245 1246 1247

4E_

1248 1249 1250

1251

1252 1253

1254 1255 1256 1257

1258

1259 1260

1261

1262

1263

4F_

1264 1265

1266

1267 1268 1269 1270

1271

1272

1273

1274 1275 1276

1277

1278

1279

50

_

1280

1281

1282 1283

1284

1285 1286

1287 1288

1289

1290

1291

1292

1293

1294

1295

51

_

1296

1297

1298 1299 1300

1301

1302 1303

1304

1305 1306 1307 1308 1309 1310

1311

52

_

1312 1313

1314

1315

1316

1317 1318 1319

1320

1321

1322

1323

1324

1325 1326

1327

53-

1328

1329 1330

1331

1332 1333

1334

1335

1336 1337

1338

1339

1340

1341

1342

1343

54

_

1344

1345

1346 1347

1348 1349

1350

1351

1352 1353 1354

1355 1356

1357 1358

1359

55

-

1360

1361

1362

1363

1364

1365

1366 1367

1368 1369

1370

1371

1372

1373

1374

1375

56

_

1376

1377

1378

1379

1380

1381

1382 1383

1384

1385 1386

1387

1388

1389

1390 1391

57

_

1392

1393

1394

1395

1396 1397

1398

1399 1400

1401

1402 1403

1404

1405 1406

1407

58-

1408

1409

1410

14ll

1412

1413

1414

1415 1416

1417

1418

1419 1420

1421

1422 1423

59

-

1424 1425 1426 1427

1428 1429 1430

1431

1432 1433 1434 1435 1436

1437

1438

1439

5A_

1440

1441

1442 1443

1444

1445 1446

1447

1448 1449 1450

1451

1452 1453

1454

1455

5B-

1456 1457

1458

1459 1460

1461

1462

1463

1464 1465

1466

1467 1468

1469

1470

1471

5C_

1472 1473

1474

1475 1476

1477

1478

1479 1480

1481

1482 1483

1484

1485 1486

1487

5D_

1488 1489 1490

1491

1492

1493

1494

1495 1496 1497 1498

1499

1500

1501

1502

1503

5E_

1504

1505

1506 1507 1508 1509 1510

15ll

1512

1513 1514 1515

1516 1517

1518

1519

5F-

1520

1521

1522

1523

1524 1525 1526

1527

1528

1529 1530

1531

1532 1533

1534

1535

47

.! 0 1 2 3 4 5 6 7 8 9 A B C D E F

6of=ti536

1537 1538 1539

1540

1541

1542

1543

1544 1545

1546 1547 1548 1549 1550

1551

61

_

1552 1553

1554

1555 1556

1557

1558

1559

1560

1561

1562 1563

1564

1565

1566 1567

62

_

1568 1569

1570

1571

1572

1573

1574

1575 1576 1577 1578 1579 1580

1581

1582 1583

63_

1584

1585

1586 1587

1588

1589 1590

1591

1592 1593 1594

1595 1596 1597 1598 1599

64

_

1600

1601

1602

1603

1604

16005

1606

1607

1608

1609 1610

1611

1612 1613 1614 1615

65

_

1616

1617

1618

1619

1620

1621

1622 1623

1624

1625

1626

1627

1628 1629 1630

1631

66_

1632

1633 1634 1635 1636 1637 1638

1639

1640

1641

1642 1643

1644 1645

1646

1647

67

_

1648

1649

1650

1651 1652

1653

1654 1655 1656 1657

1658 1659 1660

1661

1662 1663

68_

1664

1665 1666

1667 1668

1669

1670

1671

1672 1673 1674 1675

1676

1677

1678 1679

69

_

1680

1681

1682 1683

1684

1685 1686 1687 1688 1689

1690

1691

1692 1693 1694 1695

6A_

1696

1697 1698

1699

1700

1701

1702

1703

1704

1705

1706

1707

1708 1709 1710

1711

6B_

1712 1713 1714

1715

1716

1717

1718 1719

1720

1721

1722 1723 1724 1725 1726 1727

6C_

1728 1729

1730

1731

1732 1733 1734

1735

1736

1737 1738

1739

1740

1741

1742 1743

6D_

1744

1745

1746

1747

1748

1749 1750

1751 1752

1753

1754 1755

1756 1757 1758 1759

6E_

1760

1761

1762 1763

1764

1765

1766 1767

1768

1769

1770

1771

1772

1773 1774

1775

6F _

1776

1777

1778

1779

1780

1781

1782 1783

1784

1785

1786 1781 1788 1789 1790

1791

70_

1792 1793 1794 1795 1796

1797

1798 1799

1800

1801

1802

1803

1804 1805 1806 1807

71_

1808 1809

1810

1811

1812

1813

1814

1815

1816 1817

1818

1819

1820

1821

1822 1823

72

_

1824 1825

1826

1827

1828

1829

1830

1831 1832

1833 1834 1835

1836 1837 1838 1839

73_

1840

1841

1842

1843

1844

1845

1846 1847

1848

1849

1850

1851

1852

1853 1854

1855

74

_

1856

1857 1858 1859

1860

1861

1862 1863

1864

1865 1866 1867 1868 1869

1870

1871

75

_

1872 1873

1874 1875

1876 1877

1878 1879

1880

1881

1882 1883 1884

1885 1886 1887

76

_

1888 1889

1890

1891 1892

1893 1894

1895

1896

1897 1898 1899

1900

1901

1902

1903

77

_

1904 1905

1906

1907

1908

1909

1910

1911

1912

1913

1914

1915

1916

1917

1918 1919

78

_

1920

1921

1922 1923

1924

1925

1926 1927

1928

1929

1930

1931

1932 1933

1934 1935

79_

1936 1937

1938 1939

1940

1941

1942

1943

1944

1945 1946 1947 1948 1949

1950

1951

7A_

1952 1953

1954 1955

1956

1957

1958 1959

1960

1961

1962 1963

1964

1965 1966 1967

7B_

1968

1969 1970

1971 1972

1973 1974 1975 1976

1977 1978

1979 1980

1981

1982

1983

7C_

1984

1985

1986

1987

1988

1989 1990

1991

1992

1993

1994

1995

1996

1997 1998 1999

7D_ 2000

2001

2002 2003

2004

200.5

2006

2007

2008

2009 2010

2011

2012 2013 2014 2015

7E_

2016

2017

2018 2019

2020

2021

2022 2023

2024

2025 2026 2027 2028 2029 2030

2031

7F_

2032 2033 2034 2035

2036

2037

2038 2039 2040

2041

2042 2043 2044 2045 2046

2047

0 1 2 3 4 5 6 7 8 9 A B C D E F

80_

2048

2049 2050

2051

2052

2053 2054 2055

20056

2057 2058 2059 2060

2061

2062

2063

81_

2064

2065

2066 2067

2068

2069 2070

2071

2072

2073 2074 2075 2076 2077 2078

2079

82

_

2080

2081

2082 2083

2084

2085 2086 2087

2088

2089 2090

2091

2092 2093 2094

2095

83_

2096

2097 2098 2099

2100

2101

2102 2103

2104

2105 2106 2107 2108 2109 2110

2111

84

_

2112

2113 2114 2115

2116

2117

2118 2119

2120

2121

2122 2123 2124 2125 2126 2127

8.'5_

2128

2129 2130

2131 2132

2133 2134

2135 2136 2137 2138 2139 2140

2141

2142 2143

86_

2144

2145

2146 2147

2148

2149

2150

2151

2152 2153

2154

2155 2156 2157 2158 2159

87

_

2160

2161

2162 2163

2164

2165 2166 2167 2168

2169 2170

2171

2172 2173 2174 2175

8tL

2176

2177

2178 2179

2180

2181

2182 2183

2184

2185 2186 2187 2188 2189 2190

2191

89_

2192

2193 2194

2195

2196

2197

2198 2199 2200

2201

2202 2203 2204 2205 2206 2207

8A_

2208

2209 2210

2211 2212

2213

2214

2215

2216 2217

2218 2219 2220

2221

2222 2223

813_

2224

222.5

2226 2227

2228

2229 2230

2231

2232

2233

2234

2235 2236 2237 2238 2239

8C_

2240

2241

2242 2243

2244

2245

2246 2247

2248

2249 2250

2251

2252 2253 2254 2255

8D_

22.56

2257

2258 2259

2260

2261

2262 2263

2264

2265 2266 2267 2268 2269 2270

2271

8E_

2272

2273

2274

2275

2276 2277

2278 2279

2280

2281

2282 2283 2284 2285 2286 2287

8F _

2288

2289 2290

2291 2292

2293

2294

2295

2296

2297 2298 2299 2300

2301

2302 2303

90_

2304

2305 2306 2307

2308

2309 2310

2311

2312 2313

2314 2315 2316 2317 2318 2319

91

_

2320

2321

2322 2323

2324

2325 2326 2327

2328 2329

2330

2331

2332 2333 2334 2335

92

_

2336

2337

2338 2339

2340

2341

2342

2343

2344 2345

2346 2347 2348 2349 2350

2351

93

_

2352

2353 2354 2355

2356

2357 2358 2359 2360

2361

2362 2363 2364 2365 2366 2367

94

_

2368

2369

2370

2371

2372

2373

2374

2375 2376 2377 2378 2379 2380

2381

2382 2383

95

_

2384

2385 2386 2387

2388

2389 2390

2391

2392 2393

2394

2395 2396 2397 2398 2399

96

_

2400

2401

2402 2403

2404

2405 2406

2407

2408 2409 2410

2411

2412 2413 2414 2415

97

_

2416

2417

2418 2419 2420

2421

2422 2423

2424

2425 2426 2427 2428 2429 2430

2431

98

-

2432

2433 2434 2435

2436 2437

2438 2439 2440

2441

2442 2443 2444 2445 2446 2447

99

_

2448

2449 2450

2451

2452

2453

2454 2455 2456

.2457

2458 2459 2460

2461

2462 2463

9A_

2464 2465

2466 2467

2468

2469 2470

2471

2472 2473 2474 2475 2476

2477

2478 2479

9B_

2480

2481

2482 2483

2484

2485

2486

2487 2488 2489 2490

2491

2492 2493 2494 2495

9C_

2496

2497

2498 2499

2.500

2501

2502 2503 2504 2505 2506 2507 2508 2509 2510 2511

90_

2512

2513 2514 2515

2516

2517 2518 2519 2520

2521

2522

2523 2524 2525 2526 2527

9E_

2528 2529 2530

2531

2532 2533

2534

2535

2536

2537 2538 2539 2540

2541

2542 2543

9F _

2544

2545 2546 2547 2548 2549 2550

2551

2552 2553 2554 2555 2556 2557 2558 2559

48

I 2 3 4 5 6 7 8 9 A B C D E

~HO

1 F

AO

_

2.560

2561

2562

2563 2564 2565 2566 2567 2568

2569

2570

2571

2572 2573 2574

2575

Al _

2576 2577 2578

2579 2580

2581

2582

2583

2584

2585 2586 2587 2588 2589

2590

2591

A2

_

2592 2593

2594

2595

2596

2597

2598

2599 2600

2601

2602

2603

2604

2605 2606

2607

A3

_

2608 2609 2610

2611

2612 2613

2614 2615

2616

2617 2618

2619 2620

2621

2622 2623

A4

_

2624

262.5

2626 2627

2628 2629 2630

2631

2632 2633

2634

2635

2636

2637

2638

2639

A5

_

2640

2641

2642 2643 2644

2645 2646

2647

2648 2649 2650

2651

2652 2653

2654 2655

A6

_

2656 2657 2658 2659

2660

2661

2662

2663

2664

2665

2666

2667 2668

2669 2670

2671

A7

_

2672

2673

2674

2675 2676

2677 2678

2679 2680

2681

2682

2683

2684 2685

2686

2687

A8

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2688

2689

2690

2691

2692

2693 2694

2695

2696 2697 2698

2699 2700

2701

2702 2703

A9

_

2704

2705

2706 2707

2708

2709

2710

2711

2712

2713

2714

2715

2716 2717

2718 2719

AA_

2720

2721

2722

2723

2724 2725

2726"

2727

2728

2729 2730

2731

2732

2733 2734 2735

AB_

2736 2737 2738 2739

2740

2741

2742 2743

2744 2745 2746

2747 2748 2749 2750

2751

AC_

2752 2753

2754

2755

2756

2757

2758

2759

2760

2761

2762

2763

2764

2765 2766 2767

AD_

2768

2769 2770

2771

2772 2773

2774 2775 2776 2777

2778

2779

2780

2781

2782 2783

AE

_

2784 2785

2786 2787

2788 2789 2790

2791

2792

2793

2794

2795 2796 2797

2798

2799

AF

_

2800

2801

2802 2803

2804

2805 2806 2807

2808 2809

2810

2811

2812

2813

2814

2815

BO

_

2816 2817 2818

2819 2820

2821

2822

2823

2824

2825

2826

2827 2828

2829

2830

2831

Bl _

2832 2833

2834

2835

2836

2837

2838 2839

2840

2841

2842

2843 2844

2845 2846

2847

B2

_

2848 2849 2850

2851

2852 2853 2854

2855

2856 2857

2858

2859

2860

2861

2862 2863

B3

_

2864

2865

2866 2867

2868 2869 2870

2871

2872

2873

2874

2875 2876 2877

2878

2879

B4

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2880

2881

2882

2883

2884

2885

2886

2887 2888 2889 2890

2891

2892 2893 2894

2895

B5

-

2896 2897 2898 2899 2900

2901

2902

2903 2904 2905 2906 2907 2908

2909 2910

2911

B6

_

2912 2913

2914

2915 2916 2917 2918

2919 2920

2921

2922

2923 2924 2925

2926 2927

B7

_

2928

2929

2930

2931

2932 2933

2934

2935

2936 2937 2938

2939 2940

2941

2942

2943

B8

_

2944

2945 2946 2947

2948

2949

2950

2951

2952 2953

2954

2955

2956

2957

2958

2959

B9

_

2960

2961

2962

2963

2964

296.5

2966

2967

2968 2969

2970

2971

2972 2973

2974

2975

BA_

2976 2977 2978 2979

2980

2981

2982

2983 2984 2985 2986

2987

2988 2989

2990

2991

BB_

2992 2993 2994

2995 2996

2997

2998

2999

3000

3001

3002

3003

3004

3005

3006

3007

BC_

3008 3009 3010

3011

3012 3013

3014

3015

3016 3017 3018

3019 3020

3021

3022 3023

BD_

3024

3025

3026

3027

3028 3029 3030

3031

3032 3033

3034

3035 3036

3037

3038 3039

BE_

3040

3041

3042

3043 3044 3045

3046

3047

3048 3049

3050

3051

3052 3053 3054 3055

BF

_

3056 3057 3058

3059 3060

3061

3062 3063

3064

3065 3066 3067 3068 3069

3070

3071

0 1 2 3 4 5 6 7 8 9 A B C D E F

CO

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3072 3073

3074

3075 3076

3077 3078 3079 3080

3081

3082 3083 3084 3085

3086 3087

Cl

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3088 3089 3090

3091

3092 3093 3094 3095

3096

3097

3098

3099

3100

3101

3102

3103

C2

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3104 3105 3106 3107

3108

3109

3110

3111

3112

3113

3114

3115

3116

3117 3118 3119

C3

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3120

3121

3122 3123 3124 3125

3126

3127

3128

3129 3130

3131

3132

3133

3134

3135

C4

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3136 3137 3138

3139 3140

3141

3142

3143 3144 3145

3146

3147 3148 3149

3150

3151

C5

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3152 3153

3154

3155

3156

3157

3158

3159

3160

3161

3162

3163

3164 3165

3166 3167

C6

_

3168

3169

3170

3171

3172

3173

3174

3175 3176

3177

3178

3179 3180

3181

3182 3183

C7

_

3184

3185

3186 3187

3188

3189

3190

3191

3192

3193

3194 3195

3196

3197

3198 3199

C8

-

3200

3201

3202 3203 3204 3205

3206

3207 3208

3209

3210

3211

3212 3213 3214

3215

C9

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3216

3217

3218 3219

3220

3221

3222

3223

3224

3225 3226 3227 3228

3229 3230

3231

CA_

3232

3233 3234 3235 3236 3237

3238

3239 3240

3241

3242

3243

3244

3245 3246

3247

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3248 3249 3250

3251

3252

3253

3254

3255

3256 3257 3258

3259

3260

3261

3262 3263

CC_

3264

3265 3266

3267

3268 3269

3270

3271

3272 3273

3274

3275

3276 3277 3278

3279

CD_

3280

3281

3282

3283 3284 3285

3286

3287 3288 3289 3290

3291

3292

3293 3294

3295

CE_

3296

3297 3298

3299 3300

3301

3302

3303 3304 3305

3306

3307

3308

3309 3310

3311

CF

_

3312 3313 3314 3315

3316

3317

3318

3319

3320

3321

3322

3323

3324 3325

3326 3327

DO_ 3328 3329

3330

3331

3332 3333

3334

3335 3336 3337 3338 3339

3340

3341

3342 3343

Dl_

3344 3345 3346 3347 3348

3349 3350

3351

3352 3353

3354

3355 3356 3357 3358

3359

D2

_ 3360

3361

3362 3363

3364

3365

3366

3367 3368

3369

3370

3371

3372 3373 3374

3375

D3_

3376 3377 3378

3379 3380

3381

3382

3383 3384 3385

3386

3387 3388 3389 3390

3391

D4

_

3392

3393

3394 3395

3396

3397

3398

3399

3400

3401

3402

3403

3404

3405 3406 3407

D5

_

3408 3409 3410

3411

3412

3413

3414

3415

3416

3417

3418

3419 3420

3421

3422 3423

06

_

3424

3425

3426 3427 3428

3429 3430

3431

3432 3433

3434

3435 3436 3437

3438 3439

D7_

3440

3441

3442 3443 3444

3445

3446

3447 3448 3449

3450

3451

3452

3453

3454

3455

D8_

3456 3457 3458 3459 3460

3461

3462

3463

3464

"3465

3466

3467 3468 3469

3470

3471

D9_

3472

3473

3474

3475 3476

3477

3478

3479

3480

3481

3482

3483 3484 3485

3486

3487

DA_

3488

3489

3490

3491

3492

3493

3494

3495

3496 3497

3498

3499

3500

3501

3502 3503

DB_

3504

3505

3506 3507

3508 3509 3510

3511

3512 3513 3514 3515 3516

3517 3518 3519

DC_ 3520

3521

3522 3523 3524

3525

3526

3527 3528

3529

3530

3531

3532 3533 3534 3535

DD_

3536 3537 3538 3539 3540

3541

3542

3543 3544 3545

3546

3547

3548

3549

3550

3551

DE_

3552

3553

3554

3555

3556 3557

3558 3559

3560

3561

3562

3563 3564 3565 3566

3567

DF_

3568

3569 3570

3571

3572 3573 3574 3575

3576

3577

3578

3579 3580

3581

3582 3583

49

+-to

1 2 3 4 5 6 7 8 9 A B C D E F

Eo_

3584

3585 3586

3587 3583 3589 3590

3591

3592

3593

3594

3595

3596 3597 3598 3599

El_

3600

3601

3602

3603

3604 3605 3606 3607

3608

3609 3610 .

3611

3612 3613 3614

3615

E2-

3616

3617

3618

3619

3620

3621

3622

3623 3624

3625

3626

3627

3628

3629

3630

3631

E3-

3632

3633 3634

3635 3636 3637

3638

3639

3640

3641

3642

3643

3644

3645 3646

3647

E4_

3648 3649 3650

3651

3652

3653

3654

3655 3656 3657 3658 3659

3660

3661

3662

3663

E5_

3664

3665

3666

3667 3668 3669 3670

3671

3672

3673

3674 3675 3676

3677

3678 3679

E6_

3680

3681

3682

3683

3684

3685 3686 3687

3688

3689 3690

3691

3692

3693

3694

3695

E7

_

3696

3697 3698

3699 3700

3701

3702 3703

3704

3705 3706

3707

3708 3709 3710

3711

E8_

3712

3713 3714

3715 3716 3717

3718

3719 3720

3721

3722

3723 3724

3725

3726 3727

E9_

3728

3729

3730

3731

3732 3733

3734 3735 3736

3737

3738 3739

3740

3741

3742

3743

EA_

3744

3745

3746

3747 3748 3749 3750

3751

3752

3753

3754

3755

3756 3757

3758

3759

EB_

3760

3761

3762

3763

3764 3765 3766

3767

3768

3769 3770

3771

3772

3773

3774

3775

EC_

3776

3777

3778 3779 3780

3781

3782 3783

3784

3785

3786 3787

3788

3789 3790

3791

ED_

3792

3793

3794

3795

3796

3797

3798

3799 3800

3801

3802

3803 3804

3805 3806 3807

EE_

3808 3809 3810

3811

3812

3813

3814

3815 3816

3817

3818

3819 3820

3821

3822

3823

EF_

3824

3825

3826 3827 3828 3829 3830

3831

3832

3833

3834

3835 3836

3837 3838 3839

FO_

3840

3841

3842 3843

3844

3845

3846

3847 3848

3849 3850

3851

3852

3853

3854

3855

Fl_

3856

3857

3858 3859 3860

3861

3862 3863

3864

3865 3866

3867

3868

3869

3870

3871

F2 _

3872

3873 3874

3875 3876

3877 3878

3879 3880

3881

3882

3883 3884

3885

3886

3887

F3

_

3888 3889

3890

3891

3892 3893

3894

3895 3896 3897

3898

3899 3900

3901

3902

3903

F4

_

3904

3905

3906 3907

3908 3909

3910

3911

3912

3913

3914

3915

3916 3917 3918 3919

F5

_

3920

3921

3922

3923

3924

3925 3926 3927 3928

3929 3930

3931

3932

3933

3934

3935

F6_

3936

3937

3938 3939

3940

3941

3942 3943

3944

3945

3946 3947

3948 3949 3950

3951

F7_

3952

3953

3954

3955

3956

3957

3958 3959

3960

3961

3962

3963

3964

3965 3966 3967

F8_

3968

3969

3970

3971

3972 3973

3974 3975

3976

3977 3978

3979

3980

3981

3982 3983

F9_

3984 3985

3986

3987

3988 3989 3990

3991

3992 3993

3994

3995 3996

3997

3998

3999

FA_

4000

4001

4002 4003

4004 4005

4006 4007

4008

4009

4010

4011

4012 4013 4014

4015

FB_

4016

4017 4018

4019 4020

4021

4022

4023 4024 4025

4026

4027

4028

4029

4030

4031

FC-

4032 4033

4034

4035

4036 4037 4038 4039 4040

4041

4042

4043

4044

4045 4046

4047

FD_

4048

4049

4050

4051

4052 4053

4054

4055 4056 4057

4058

4059

4060

4061

4062

4063

FE_

4064 4065

4066

4067

4068 4069

4070

4071

4072 4073 4074

4075

4076 4077

4078 4079

FF_

4080

4081

4082

4083

4084

4085 4086 4087

4088

4089

4090

4091

4092

4093

4094

4095

50

COMMAND

Control

NoOp

Release*

Restore

Seek

Cylinder

Seek Head

Sense

I/O

Set File Mask

Space

Record

Transfer

in

Channel

Search Home Address Equa I

Identifier Equal

Identifier High

Identifier Equal or High

Key Equal

Key High

Key Equal or High

Key and Data Equa

1*

Key and Data High*

Key and Data Equal or High*

Read Home Address

Count

Record

RO

Data

Key

and Data

Count,

Key

and

Data

Write

Home Address

Record

RO'

Count,

Key and Data

Special

Count,

Key and Data*

Data

Key and Data

* Special Feature

X

Not

Significant

COMMAND CODE

Multiple

Track

Off

Decimal Hexadecimal Binary Decimal

03 03

0000 0011

23

1 7 0001 0111

19

13

0001 0011

07

0000 0111

11

OB

0000 1011

2 7 1 B 0001 1011

04

0000 0100

3 1 1 F 0001 1111

15

OF 0000 1111

X8

XXXX

1000

57

39

0011 1001

185

49

3 1 0011 0001

177

8 1 5 1 0101 0001

209

1 1 3

71

0111 0001

241

4 1

29

0010 1001

169

73

49

0100 1001

:2

0 1

105

69

0110 1001

233

45

20

0010 1101 1

73

77

40

0100 1101

205

109

60

0110 1101

237

26

lA

0001 1010

154

18

1 2 0001 0010

146

22

1 6 0001 0110

150

06

0000 0110

134

14

OE

0000 1110

142

30

1 E 0001 1110

158

25

1 9 0001 1001

2 1

15

0001 0101

29

10

0001 1101

01

a 1 0000 0001

05

00000101

13

00

0000 1101

Multiple

Track

On

(If

Applicable)

Hexadec i

rna

I Binary

DATA

ADDRESS

COUNT

X X

}

CPU

storage

location

of

seek

address 6

6

CPU

storage

location

to

which four 4

sense bytes

are

sent

CPU

storage

location

of mask

byte

1

X X

CPU

storage

location

of

(Must

be

divisible by 4)

B 9 1011 1001 \ 4

(usuaIlY~

8 1

10110001

) 5 (usually

o 1

11010001

5 (usually)

F 1 1111 0001 ! CPU storage

location

of

search

5 (usually)

A9

1010 1001 From 1

to

255

C9

1100 1001 ( argument

From

1 to 255

E 9 1110 1001

From

1 to 255

AD

1010 1101 ) }

Number

of

bytes lincluding

CD

11001101

mask bytes} in search argument

ED

1110 1101 I

9A

1001 1010 5

92

1001 0010 8

96

10010110

\

CPU

,to'age

10coHon

to

whkh

0'00'

Number of bytes

to

be

transferred

86

10000110

read

will

be

transferred Number

of

bytes

to

be transferred

8 E 1000 1110 Number

of

bytes

to

be transferred

9 E 1001 1110 Number

of

bytes

to

be transferred

5 {usually}

8+Key Length + Data Length of

Record

RO

i

CPU

"o'age

10coHon

f'om whkh

0'00'

8+Key Length + Data Length

to

be

written

will

be

transferred 8+Key Length +

Data

Length

Data Length

Key Length + Data Length

A26-5988-2

As

there

is

no unique physical address associated with

each

record on a given

track,

the

2841

must

have

some means of

locating

these

records. There

are

seven states of

orientation

with respect

to

a

track

in

the

2841

that

are

used

to

accomp-

lish this.

1. Index Point

State

-

Gap

between Index Point and

Home Address.

2.

Home Address

State

-

Gap

between Home Address

and

RO.

3.

Count

State

-

Gap

between

Count

and

Key

Fields.

4.

Key

State

-

Gop

between Key and Data

Field.

5.

Data

State

-

Gap

between Data Field

and

succeeding

Address Mark or Index Point if this

is

the

lost record on

the

track.

6.

Address Marker

State

-

Gop

between Address

Mark

and

Count

Field.

7.

Reset

Orientation

State

-

None

of

the

above.

The Reset

Orientation

State,

while not associated with

any

specific

area

of a

track

does not necessarily imply

that

the

2841 has lost

orientation.

Any time a

CCW

chain

is

broken or a Control Command

is

performed, the 2841

is

set

Command

Command Prerequisite

Read CKD

None

Read

KD

None

None

Write CKD Search Equal

(also Write Count or Key

Special CKD) Write

CKD

Write

R~

Write

KD

Search Equal

Count of Key

Write 0 Search Equa I

Count or Key

Search 10

None

Search Key

None

Searc:h Home

None

Address

Read

R~

None

Write

R~

Search Equal

Home Address

Write

HA

Read

HA

None

Write

HA

None

Read

IPl

None

Read Count

None

Control

Space

Search (any)

Record Read (any)

Control Erose Write

CKD

Write

R~

Control

NOP

None

International

Business Machines Corporation

. Data Processing Division

112

East

Post Road, White Plains,

N.

Y.

10601

APPENDIX

D.

TRACK

ORIENTATION

to

this

state.

The next

data

command

(i.

e.,

read,

write or

search) further defines this

state

to

one of

the

three

sub-

states

below.

1. Reset

Orientation

to Index Point

State

(ROIP).

Orientation

state

is

set

to

Index Point

State

upon

detection

of

the

Index Point on

the

tra.ck.

2.

Reset

Orientation

to Address Marker

State

(ROAM).

Orientation

is

set

to

Address Marker

State

upon

detection

of any Address Marker.

3.

Reset

Orientation

to

Address Marker or Index Point

State

(ROAM or IP).

Orientation

is

set

to

either

Index Point

State,

upon

detection

of

the

Index

Poi

fit,

or to Address Marker

State

upon

detection

of

any Address Marker, whichever occurs first.

Read,

Write,

Search and some Control commands in

the

2841

have

two types of prerequisities

that

must

be

satisfied

to insure proper operation of

the

command.

By

considering

command

sequence

restrictions

and

orientation

requirements,

all

vol id command sequences

can

be

constructed and

the

re-

sult of

their

execution

predetermined. The following

table

illustrates these two prerequisities and

the

resulting

orientation

state

for

all

data

commands:

Valid

Orientation

State

at

Beginning

at

Completion of

of

Command Command

ROAM Data

Count Data

ROAM

Count Data

Key

ROAM

Count Data

Key

Data

Count Data

ROAM

Count Data

Key

ROAM or

IP

Count

ROAM Key

Count

ROIP Home Address

Home Address Data

ROIP

Home Address Data

ROIP Home Address

ROAM Data

ROAM Count

Count Reset

Orientation

Key

Count Reset

Orientation

Key

Data

None

Reset

Orientation

A26 5988 2_2841_2302_2311_2321_2303_Component_Descriptions_Oct65 2 2841 2302 2311 2321 2303 Component Descriptions Oct65

A26-5988-2_2841_2302_2311_2321_2303_Component_Descriptions_Oct65 A26-5988-2_2841_2302_2311_2321_2303_Component_Descriptions_Oct65

A26-5988-2_2841_2302_2311_2321_2303_Component_Descriptions_Oct65 A26-5988-2_2841_2302_2311_2321_2303_Component_Descriptions_Oct65

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