Ibm 2250 3 User manual

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Systems Reference Library

IBM

System/360

Component Description

IBM

2250

Display Unit Model 3

IBM

2840

Display Control Model 2

This

document

presents

detailed

information

about

IBM 2250

Display

Unit

Model

3/IBM

2840

Display

Control

Model

2

pro-

gramming,

operation,

and

special

features.

The

material

is

presented

with

the

assumption

that

the

reader

has

read

the

IBM

System/360

Principles

of

Operation

manual,

Form

GA22-6821.

The

following

publications

may

also

be

of

interest

to

the

reader:

• IBM

System/360

Component

Description:

IBM 2250

Display

Unit

Model

1,

Form

GA27-2701.

• IBM

System/360

Operating

System,

Graphic

Programming

Services

for

IBM 2250

Display

Unit,

Form

GC27-6909,

File

No.

8360-03

Form

GA27-2721-1

Second

Edition

(March,

1971)

This

edition,

Form

GA27-2721-1,

incorporates

information

contained

in

Technical

Newsletter

N27-2934

pertaining

to

the

Display

Copier

attachment.

This

edition

obsoletes

Form

GA27-2721-0

and

Technical

Newsletter

N27-2934.

Changes

are

indicated

by

a

vertical

line

to

the

left

of

the

change.

Copies

of

this

and

other

IBM

Publications

can

be

obtained

through

IBM

Branch

Offices.

Address

comments

concerning

the

contents

of

this

publication

to:

IBM

Corporation,

Product

Publications,

Dept.

528,

Kingston,

New

York 12401

©

International

Business

Machines

Corporation

1967, 1971

INTRODUCTION •

2250

OPERATIONS

General

Displays

Vectors

and

Points .

Characters

Light

Pen.

Alphameric

Keyboard.

Programmed

Function

Keyboard

2840

OPERATIONS WITH ATTACHED

2250's

Orders

Order

Fonnat

Graphic

Mode

Orders .

Character

Mode

Orders

Control

Mode

Orders .

Light

Pen

Mode

Orders

Display

Regeneration

.

Display

Regeneration

Timing

2840

OPERATIONS

WITH

THE CHANNEL

Interface

Operations

.

Commands

.

Write

Buffer

Command

Read

Commands

.

Figure

1

Attachment

of

2840-2/2250-3

Configuration

to

System/

360

•

Figure

2

Example

of

a

2250

Display

•

Figure

3

Functional

Sections

of

a

2250-3

Figure

4

Display

Area

Coordinate

Addressing

System.

Figure

5

Examples

of

Display

Area

Coordinate

Address

Modification

by

the

2250

.

Figure

6

Character

Set

and

Code

Assignments

.

Figure

7

Character

Grid

Coordinate

System

Figure

8

Strokes

that

Fenn

the

Letter

"A"

Figure

9

Character

and

Line

Spaces

Figure

10

Fiber

Optic

Light

Pen

.

Figure

11

Alphameric

Keyboard.

Figure

12

Programmed

Function

Keyboard

Table

1

Character

Display

Characteristics

•

Table

2

Mode

Orders.

Table

3

Displayable

Vectors

Per

2250-3

at

a

Regener-

ation

Rate

of

40

cps

Table

4

Displayable

Vectors

Per

2250-3

at

a

Regen-

eration

Rate

of

30 cps

Table

5

Displayable

Characters

Per

2250-3

at

a

Regeneration

Rate

of

4-0

cps

5

7

8

9

10

12

15

17

20

21

23

25

26

31

32

33

34

5

7

8

9

11

12

13

14

16

11

19

28

29

30

CONTENTS

Control

Commands

Sense

Command

36

38

Instructions

• 39

Test

I/O

•

39

Halt

I/O

.

39

Examples

of 284-0/2250

Operations

39

Example

1.

Displaying

an

Image

on

One

2250

39

Example

2.

Nonnal

Light

Pen

Operation

-

2250

Equipped

with

Programmed

Function

Keyboard

. 41

Example

3.

Alphameric

Keyboard

Operation

42

Graphic

Design

Operations

42

Entities

•

42

Buffer Subroutines

43

Input

by

Light

Pen

Search

43

Input

by

Light

Pen

Tracking.

43

Feedback

by

Light

Pen

Tracking

History.

43

CONTROLS AND INDICATORS. 53

Basic

Operator

Controls

and

Indicators

53

Metering

.

54

APPENDIX A: HEXADECIMAL -DECIMAL CONVERSION

56

APPENDIX

B:

STATUS-SENSE COMBINATIONS 61

GLOSSARY

INDEX

Figure

13

Figure

14

Figure

15

Figure

16

Figure

17

Figure

18

Figure

19

Figure

20

Figure

21

Figure

22

Table

6

Table

7

Table

8

Table

9

Table

10

Table

11

Table

12

64

65

ILLUSTRATIONS

Functional

Sections

of

the

2840-2

and

a

2250-3

18

Read

Manual

Input

Command

Response . 35

Programmed

Function

Keyboard

Overlay

(Top

View)

36

Buffer

Program

Example

Display

40

Sequence

of

Routines

in

Light

Pen

Tracking

History

Programming

Example

•

47

Flow

Diagram

of

Example

Program

49

Point

Pattern

Used

in

Example

Program

51

Vector

Pattern

Used

in

Example

Program

52

2250-3

Operator

Controls

and

Indicators

.

53

2840-2

Operator

Panel

54

TABLES

Displayable

Characters

Per

2250-3

at

a

Regen-

eration

Rate

of

30

cps

30

Status

Byte Bit

Assignments

• 32

Commands

Used

with

the

284-0-2 33

Sense Bit

Assignments

38

Buffer

Program

Example

41

Sample

Entity

Routine

42

Feedback

by

Light

Pen

Tracking

History,

Example

Routine

44

IBM

2840 Display Control, Model 2

The

IBM 2250

Display

Unit Model 3

(Frontispiece)

is

a

cathode-ray-tube

(CRT)

display

console

which

can

be

attached

to

a

System/360

via

the

IBM 2840

Display

Control

Model

2.

Along

with

the

capability

of

displaying

graphic

or

alphanumeric

information,

the

2250

offers

man-machine

interaction

through

its

light

pen

and

two

keyboards.

Using

these

facilities,

a

programmer

can

furnish

computer-aided

design

capabilities

whereby

the

2250

user

can

create,

modify,

and

add

graphic

and

alphanumeric

data

into

the

system

through

the

display

screen.

This

exten-

sion

of

the

System/360

data

processing

power

is

useful

(1)

for

handling

the

graphic

information

asso-

ciated

with

scientific

and

engineering

applications,

and

(2)

for

providing

faster

and

more

effective

retrieval

and

graphic

expression

of

management

and

business

operating

data.

Programming

requirements

for

the

2250

differ

from

other

I/O

devices

in

that

the

2840

Display

Control

has

a

buffer

with

logical

capabilities

that

require

programming.

A

buffer

program

consisting

of

buffer

orders

and

data

to

be

displayed

can

be

developed

either

in

final

image

form

or

as

a

frame-

work

to

accept

data

(to

be

provided

at

object

time)

by

the

CPU

program

and

to

be

transmitted

via

a

channel

to

the

2840-2.

Under

control

of

this

buffer

program,

the

2250-3

displays

graphic

images

in

the

form

of

lines,

points

,

and

alphameric

characters.

Using

the

logical

capabilities

of

the

buffer

and

the

light

pen,

programmed

function

keyboard,

and

alphameric

keyboard,

the

programmer

can

design

and

implement

his

own

tracking,

sketching,

or

dis-

play

manipulation

techniques

with

minimum

CPU

interaction.

A

buffer

program

consists

of

orders

interleaved

with

data.

The

three

major

groups

of

orders

are

Graphic,

Character,

and

Control.

When

decoded,

an

order

sets

a

mode

of

operation

which

will

be

in

effect

until

another

order

is

encountered.

All

data

in

between

is

processed

in

that

mode.

Hence,

an

order

requesting

absolute

vectors

will

put

the

2250/2840

in

Absolute

Vector

mode,

and

all

following

data

will

be

treated

as

the

absolute

X,

Y

end

points

of

vectors

to

be

displayed

until

the

is

en-

countered.

Available

in

conjunction

with

this

basic

principle

is

the

ability

to

control

light-pen

responses

in

the

2840/2250.

These

orders

can

condition

the

2840/2250

to

accept

light-pen

detects

until

another

light-pen

order

resets

the

condition.

A

light-pen

detect

on

any

displayed

information

between

these

two

orders

is

then

accepted

and

passed

on

to

the

program

for

processing.

In

addition,

immediate

action

orders

allow

direct

transferring,

movement

of

INTRODUCTION

data

and/or

addresses,

and

storage

of

the

deflection

registers

into

a

buffer

location.

Each

2250-3

can

operate

up

to

2,000

ft.

from

the

2840-2,

allowing

access

to

the

computer

from

the

user's

normal

working

area.

Furthermore,

sharing

of

the

common

control

unit

(the 2840-2)

by

several

2250-31s

results

in

more

economical

configurations

for

the

multiconsole

environment.

The

2840-2

can

control

the

operation

of

up

to

four

2250-3

Display

Units

(Figure

1).

Light-pen

tracking

can

be

performed

simultaneously

by

the

user

of

each

2250

with

no

interference

to

System/360.

Attachment

of

the

2840-2

to

System/360

(CPU)

and

CPU

main

storage

is

via

either

a

selector

or

multiplexor

chan-

nel;

it

uses

one

of

the

eight

control

unit

positions

on

the

channel

interface.

The

channel

provides

the

2840-2

with

the

data

to

be

displayed

and

with

the

control

information

necessary

to

direct

the

operation

of

the

2840-2

and

associated

display

units.

Buffer

storage

in

the

2840

stores

digitally

coded

images

for

each

attached

2250-3.

The

buffer

enables

image

regeneration

as

well

as

message

composition

from

the

2250

alphameric

keyboards;

this

allows

the

2840-2

and

attached

2250-3's

to

operate

concurrently

with

the

computer

system,

freeing

the

CPU

and

the

channel

for

other

functions.

Buffer

storage

areas

are

program-assignable

for

any

attached

2250-3

and

can

be

varied

under

program

control.

The

2840-2

controls

the

operation

of

each

attached

2250-3.

By

means

of

shared

circuitry

and

interleaved

operations

in

the

2840-2,

each

2250-3

can

be

operated

independ-

ently,

and

different

images

can

be

generated

simul

-

taneously

on

each

display.

The

basic

2250-3

(without

special

features)

pro-

vides

the

ability

to

display

graphic

information

in

System/.360

r----

2250

Model 3

One 2840

can

control

up to

four

2250 Model 3

Display

Units

2250

Model 3

Up

to 2000 feet

IJp

to 2000 feet

;

Selector

or

Up

to

7

I Multiplexor !--------------(additional

I Channel control units

Figure

1.

Attachment

of

2840-2/2250-3

Configuration

to

System/360

Introduction

5

absolute

or

incremental

mode

in

the

form

of

points

or

straight

lines

in

any

direction;

it

can

also

display

alphameric

characters

(alphabetics,

numerics,

and

special

symbols).

In

addition,

a

light

pen

is

provided

with

the

basic

2250-3.

For

increased

intercommu-

nication

between

the

user

and

the

controlling

program,

two

keyboards

are

available

as

special

features:

Alphameric

Keyboard

-

Provides

a

typewriter-like

keyboard

with

which

the

user

can

perform

editing

functions

and

compose

messages

consisting

of

letters,

numbers,

and/

or

special

symbols

for

entry

into

2840

buffer

and

CPU

main

storage.

Programmed

Function

Keyboard

-

Provides

com-

munication

between

the

user

and

the

computer.

The

keyboard

consists

of

keys,

indicators,

and

sensing

switches

for

use

with

replaceable

descriptive

over-

lays.

The

function

of

each

key

and

indicator,

which

is

program-defined,

is

identified

to

the

program

by

the

overlay

coding

and

to

the

user

by

symbols

on

the

overlay.

The

program

associated

with

the

overlay

code

and

the

selected

key

then

directs

the

requested

operation.

For

example,

as

a

result

of

a

key

de-

pression,

the

program

might

direct

the

computer

to

enlarge,

reduce,

or

delete

the

image

displayed

by

the

associated

2250.

When a 2250

is

not

in

the

same

room

with

the

2840

and

the

CPU,

a

telephone

should

be

near

the

2250

so

that

the

2250

operator

can

communicate

with

the

CPU

installation.

The

basic

2840-2

contains

a

32,

768-byte

core

buffer,

order

mode

control,

and

a

character

gener-

ator.

The

character

generator

can

translate

one

System/360

eight-bit

byte

representation

from

an

6

alphameric

character

into

a

sequence

of

signals

which, when

converted

to

analog

deflection

signals

by

the

2250-3,

cause

the

character

to

be

drawn

on

the

2250-3

CRT

display

area.

A

standard

character

set

of

63

alphabetics,

numerics,

and

special

symbols

is

provided;

two

character

sizes

are

program-

selectable.

The

basic

2840-2

can

attach

to,

and

con-

1

trol,

two

2250-3's.

A

special

feature,

Display

Multiplexer,

is

available

for

increased

2840-2

attachment

capability:

Display

Multiplexer

-Allows

attachment

of

two

additional

2250 Model 3

Display

Units

to

the

2840-2.

A

maximum

of

one

display

multiplexer

feature

can

be

installed

on

one

2840-2,

allowing

attachment

of

up

to

four

2250-3's.

Display

Copier

Attachment

-

Permits

attachment

of

an IBM 2285

Display

Copier

to the 2250.

The

publication

Component

Description,

IBM 2285

Display

Copier,

Form

GA27-2730,

contains

a

functional

description

of,

and

operator

procedures

for,

the 2285.

The

2285

is

a

free-standing,

non-

programmed

device;

it

provides,

under

2250

operator

control,

8-1/2

by

11-inch

paper

copies

of

the

2250

display

image.

Each

copy

consists

of

a

black

image

on

a

light

gray

background.

The

2285

is

located

beside

the

left

edge

of

the

2250

reading

board;

in

this

position,

the

2285

controls,

indicators,

and

hopper

(copy

receptacle)

are

easily

accessible

to

the

2250

operator.

Basic

power

for

the

2285

is

provided

by

the

2250. Analog

signals

are

switched

from

the

2250 to the 2285

during

the

paper-exposure

portion

of

each

copy

cycle.

GENERAL

Each

2250-3,

under

control

of

a

2840-2,

generates

images

on

the

12-inch

by

12-inch

usable

display

area

of

a

21-inch

cathode-ray

tube

(CRT).

An

image

can

be

composed

of

straight

lines

(vectors)

,

points,

standard

characters

(in two

sizes),

and

special

char-

acters

formed

with

vectors

and

points

(Figure

2).

A

visible

display

is

produced

when

an

el

ectron

beam

in

the

CRT

strikes

the

phosphor-coated

CRT

screen,

causing

the

portion

of

the

coating

struck

by

the

beam

to

glow

briefly.

Normally,

the

glow

fades

within

a

fraction

of

a

second,

too

soon

for

the

human

eye

to

carefully

perceive

and

identify

the

image.

For

this

reason,

the

display

must

be

redrawn

continuously

Figure

2.

Example

of

a

2250

Display

2250

OPERATIONS

(regenerated)

at

a

rate

that

will

cause

the

display

to

appear

steady

and

stationary

to

the

observer.

Re-

generation

is

performed

automatically,

under

control

of

a

program

in

the

2840.

The

2840

accomplishes

regeneration

by

continuously

retransmitting

control

and

display

data

to

the

2250;

this

data

can

be

modified

during

regeneration

by

the

2840,

as

directed

by

the

buffer

program

and/or

the

CPU

program,

to

update

or

change

the

display.

The

2250

also

performs

various

nondisplay

services

for

the

user

by

providing

the

interface

between

the

user

and

the

problem

pro-

gram

with

the

following

devices:

1.

Programmed

function

keyboard

.

Provides

keys

and

overlays

for

user

communication

2250

Operations

7

to

the

program

and

indicators

for

program

communication

to

the

user.

2.

Alphameric

keyboard.

Enables

the

user

to

change,

edit,

or

create

character

displays.

3.

Light

pen.

Supplies

the

buffer

address

of

a

vector,

point,

or

character

at

which

the

user

is

pointing

a

pen-like

device.

This

information

can

be

used

for

operations

as

determined

by

the

program,

by

the

alpha-

meric

keyboard,

or

by

the

programmed

function

keyboard.

The

light

pen

thus

enables

the

user

to

enter

and

manipulate

graphic

information.

4.

Audible

alarm

(single-stroke

buzzer).

Enables

the

program

to

inform

the

operator

that

action

is

required.

2840

Via

Interface

Control to Channel 2840

Buffer 2840 Line Buffer

Reg

,------A---,

'

Indicator

Data

Stroke Codes

Character

Stroke

Deflection

Character

and

Cursor Keys

END and

CANCEL Keys

Audible

Alarm

Notes:

key,

overlay

codes

r

---

,

I

Programmed I

I Function I

: Keyboard I

L

_____

.J

1. Dashed blocks represent

special

feature

functions.

2.

Heavy lines

represent

data

flow.

r

---

1

: Alphameric I

I Keyboard I

L---

__

J

Figure

3,

Functional

Sections

of

a

2250-3

8

Intensity

The

functional

sections

of

the

2250

are

shown

in

Figure

3.

The

functions

represented

by

solid

blocks

are

provided

in

the

basic

units,

whereas

those

re-

presented

by

dashed

blocks

are

available

as

special

features.

Heavy

connecting

lines

represent

data

flow;

the

light

lines

represent

control

signal

routing.

DISPLAYS

Information

positioning

on

the

2250

display

area

is

controlled

by

a

display

program

resident

in

the

2840

buffer.

This

buffer

program

is

prepared

by

the

main

CPU

and

is

sent

to

the

buffer

via

a

standard

I/O

channel

operation.

The

program

specifies

electron

beam

deflection

to

horizontal

(X)

and

vertical

(Y)

coordinates

on

a

virtual

square

grid

composed

of

Coordinate

Data

Beam Bits

Main

Deflection

Assembly

Control

Various I

~---'

X-Y

Coordinates

Operator

Panel

2840 Control

,----A---,

•

Light Pen

Detect

light

Pen

possible

electron-beam~deflection

end

points.

This

grid

covers

(logically)

the

12-inch

by

12-inch

display

area

on

the

face

of

the

CRT;

it

comprises

1,

024

equally

spaced

X

positions

and

1,

024

equally

spaced

Y

positions

(Figure

4).

Positioning

data

in

the

display

program

selects

the

X

and

Y

coordinates

for

each

element

of a 2250

display

(each

point,

line

end

point,

and

character

area

centroid).

This

same

data

can

also

control

the

IBM 2280

Film

Recorder.

The

grid

of

addressable

coordinates

for

a 2250

or

2280

device

is

called

its

"raster".

The

space

between

two

sequentially

ad-

dressable

lines

on

the

raster

is

called

a

raster

unit.

A 2250

raster

unit

represents

1/1,

023

of

the

image,

whereas

a 2280

raster

unit

represents

1/4,095

of

the

same

image;

this

reflects

the

difference

in

address

resolution.

The

data

format

in

the

2840

provides

for

the

4,

096-by-4,

096-position

grid

of

the

2280

and

2282

film

units.

The

2250

maintains

program

compati-

bility

with

the

film

units

by

disregarding

the

two

low-order

bits

(binary) of

the

4,096-by-4,096

X and

Y

coordinates.

For

example,

a

binary

configuration

1111 1111 1111 (4, 095

decimal)

in

the

2840

is

inter-

preted

by

the

2250

as

1111111111,

or

1,023

decimal.

Thus,

each

display

element

is

positioned

by

the

2250

at

a

set

of

1,024-by-1,024

2250

coordinates

that

are

virtually

equivalent

to

the

set

of

4,

096-by-4,

096

film

unit

coordinates.

The

maximum

shift

in

the

image

caused

by

this

conversion

is

three-fourths

of

a 2250-

raster

unit

(three

2280

raster

units),

a

shift

that

is

not

noticeable

to

the

user

(Figure

5)

.

1023

(FFF)-----------------.

X=0256 (400)

y 0512

(BOO)------,

Y~0512

(BOO)

Axis

0256 (400)

012B

(200)

0064 (100)

0000

(000)1-1-.....--..---..l~----r--------t

0000Io

12B

0256

(OOOll

(200)

(400)

0064

(JOO)

Note:

0512

(BOO)

X Axis

Numbers in parentheses are hexadecimal equivalents of

1023

(fFf)

the

coordinates as they appear (in 12-bit farm) in the 2840 buffer.

Figure

4.

Display

Area

Coordinate

Addressing

System

2250

Coordinates~

\

0255

2048

(BOO)

0000+---+-~---t

0000 1028 2048 4095

(404)

(ROO)

(FFF)

0256 0257

025B

0259

0514

L.L..Lil-l-...J-l-l-..l-l-1-+4-l-+4-1--<

2056

(BOB)

y

Notes:

LL...l_Jl-l--~-1--1--1-l----l-4-l----l-4[/I-+--'

2054

0513

~-l-l>--!--l-l-++--l-+-+-1-+-+-1~_,._.

2052

(B04)

0512

~4->--!--1-1>--i-~H-+-l-++-l-i-<

204B

(BOO)

0511

L..l.._l_L.-A_l_l-l-...l_Jl-l--1--1-1--1--1~

2044 (7FC)

0510

a-'11"4---1-4-1-+4-l-+-+-+-.i-+-+-+-4-t

2040

(7F8)

1020

(3FC) 1024

(400) 1028

(404)

,,..___

_____

x 1032

(408) 1036

(40C)

~Film

Unit

Coordinates

1.

X Position specified

by

'.1840

duto.

2,

e

..

Position

selected

by

2250

from

this

data.

3.

Numbers in

parentheses

are

hexcidecimol

equivalents.

Figure

5.

Examples

of

Display

Area

Coordinate

Address

Modification

by

the

2250

NOTE: Subsequent

use

of

the

term

"raster

unit"

in

this

publication

refers

to

1/1,023

of

the

image.

Also,

this

1,023-by-1,023-raster

unit

grid

is

called

the

"reference"

grid.

Vectors

and

Points

During

vector

or

point

display

operations,

position-

ing

data

from

the

2840

directs

electron

beam

move-

ment

(deflection)

on

the

1,023-by-1,023

raster

unit

display

area.

The

2840

first

sets

the

2250

mode

of

operation

(in

this

case,

to

display

vectors

or

points).

It

then

transmits

a

set

of

positioning

data

to

the

2250

for

each

vector

or

point

to

be

displayed.

Each

set

of

positioning

data

addresses

one

X,

Y

coordinate

to

which

the

electron

beam

is

to

be

re-

positioned.

Beam

deflection

is

always

from

the

previously

addressed

coordinate,

where

the

beam

is

currently

positioned,

to

the

new

coordinate.

If

vectors

are

specified

by

the

2840,

the

beam

is

turned

on

as

it

is

being

repositioned,

displaying

a

line

be-

tween

the

current

position

and

the

new

coordinate

specified;

if

points

are

specified,

the

beam

is

turned

on

after

it

has

been

repositioned,

displaying

a

point

at

the

new

coordinate.

Points

plotted

4

or

more

raster

units

apart

can

be

distinguished

by

the

user

as

distinct

points.

2250

Operations

9

The

2250

can

also

"position"

the

electron

beam

without

causing

a

visible

line

or

point

to

appear

on

the

display.

This

capability

is

used

(1)

to

select

a

starting

location

for

displaying

characters

and

(2)

to

start

the

display

of

a new

set

of

vectors.

Each

set

of

positioning

data

from

the

2840

contains

a

beam

control

(blanking)

bit,

which

specifies

whether

the

2250

is

to

display

(unblank)

or

is

not

to

display

(blank)

the

resulting

vector

or

point.

Control

signals

from

the

2840

specify

not

only

the

type

of

operation

(vector

or

point)

to

be

performed

but,

also,

a

coding

format

for

positioning

data

that

will

be

used

during

the

operation.

Positioning

data

can

be

in

either

of

two

basic

coding

formats,

absolute

or

incremental.

Absolute

positioning

data

specifies

the

actual

X,

Y

coordinates

to

which

the

beam

is

to

be

deflected.

Each

group

of

four

eight-bit

absolute

data

bytes

addresses

one

coordinate

on

the

reference

grid

(i.

e.

,

x = 0512 ' y = 1016).

Incremental

positioning

data

specifies

the

amount

and

direction

of

beam

deflection

relative

to

the

cur~

rent

beam

position.

Each

pair

of

eight-bit

incre-

mental

data

bytes

specifies

one

increment

(up

to

X = +63

or

-64

, Y =

+63

or

-64,

a

displacement

of

0.

74 inch)

of

beam

deflection.

For

example,

if

the

current

beam

position

on

the

reference

grid

is

X = 0512, Y =

1016,

and

if

a

pair

of

incremental

data

bytes

specifies

X =+20, Y =

-40,

beam

deflection

will

be

to

position

X =

0532,

Y = 0976

on

the

refer-

ence

grid.

Thus,

the

±X,

±Y

incremental

value

is

added

to

the

absolute

value

of

the

current

beam

posi-

tion,

resulting

in

a new

absolute

value

for

the

new

beam

position.

When

incremental

data

causes

the

beam

to

move

outside

the

reference

grid

area

but

when a

total

dis-

placement

of

1,023

raster

units

beyond

the

perimeter

in

the

X

or

Y

direction

is

not

exceeded,

the

vectors

and/or

points

so

displaced

will

be

blanked.

The

X,

Y

deflection

registers

will

contain

the

value

of a

wrap-around

position.

Unless

the

displacement

limit

of

1,023

raster

units

is

exceeded,

the

displaced

beam

can

be

returned

to

the

normal

grid

area;

then,

displaying

will

resume

when

positioning

data

specifies

an

unblanked

deflection

that

is

entirely

within

the

normal

display

area.

When a

portion

of

a

display

is

blanked

because

of

a

beam

displacement

condition,

the

2840

program

can

specify

an

absolute

positioning

operation

to

the

2250,which

will

reset

the

displacement

blanking

con-

dition.

However,

if

the

first

absolute

data

bytes

received

by

the

2250 following

this

positioning

operation

specify

an

unblanked

vector,

a

line

will

be

drawn

from

the

wrap-around

position

to

the

specified

location.

Electron

beam

deflection

to

the

previously

ad-

dressed

coordinate

can

still

be

in

progress

when

10

the

data

is

received.

When

the

deflection

currently

in

process

is

completed,

the

blanking

bit

is

sent

to

the

intensity

control

section,

and

the

new

X,

Y

coordinates

are

sent

to

the

main

deflection

section.

The

main

deflection

section

applies

X and Y

analog

values

for

the

current

beam

position

to

the

deflection

coil

of

the

CRT

until

new

positioning

data

is

received.

When

the

new

data

is

received,

the

analog

values

start

changing

to

reflect

the

new

position.

As

the

analog

values

change,

the

beam

moves,

causing

the

image

to

be

displayed.

If

the

blanking

bit

specifies

a

blanked

vector

or

point,

the

beam

moves

without

being

displayed.

If

the

blanking

bit

specifies

an

unblanked

vector

or

point,

the

electron

beam

is

deflected

and

unblanked,

as

required,

to

form

a

vector

or

point

as

previously

specified

by

the

2840.

The

X,

Y

position

registers

in

the

main

deflection

section

always

contain

the

absolute

X,

Y

address

of

the

current

beam

position

in

digital

form;

the

2840

can

retrieve

this

data

and

the

blanking

bit,

rec

on-

structing

the

most

recent

positioning

data.

Characters

A

standard

set

of

characters

can

be

displayed

in

either

of two

sizes

by

a 2250;

this

set

consists

of

63

alphabetics,

numerics,

and

special

symbols

(Figure

6)

. Any

characters

that

are

not

in

this

set

can

be

created

with

vectors

and/or

points.

In

Character

mode,

the

X,

Y

coordinate

(on

the

1,

0

24-by-1,

024

reference

grid)

at

which

the

electron

beam

is

currently

positioned

becomes

the

center

point

of

a

basic-size

or

large-size

character

area.

The

2840

specifies

the

character

size,

which

is

maintained

throughout

one

Character

mode

operation.

The

beam

must

be

positioned

by

the

program

to

a

starting

coordinate

by

a

blanked

point

or

vector

be-

fore

a

character

display

operation

is

started.

The

character

area

is

divided

into

a

grid

format

of

8X-

by-8Y

addressable

points

of

which

7X and

SY

are

used

(Figure

7).

Character

grid

points

do

not

coin-

cide

with

the

1,

024-by-1,

024

main

deflection

grid

points.

Characters

are

drawn

in

this

area

with

a

series

of

high-speed

deflections,

or

"strokes".

An

average

of

six

such

strokes

is

required

to

form

one

character.

Each

stroke

end

point

is

specified

by

an

X,

Y

character

grid

coordinate

sent

from

2840

to

the

character

deflection

section

(Figure

3).

This

section

converts

each

coordinate

to

X and Y

analog

signals,

which

are

applied

to

the

high-speed

char-

acter

stroke

deflection

coil

of

the

CRT.

The

main

deflection

system

and

the

character

deflection

system

operate

independently.

The

main

deflection

system

maintains

the

current

beam

posi

-

tion

(the

center

point

of

the

character

grid)

by

Character

Codes

(Hexadecimal)

(see notes)

Bits Bits

0-3

4-7

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

0 NUL

SP

& -0

l I A*

J*

A J 1

2

B*

K*

s·

B K s 2

3

C'

l*

T*

c L T 3

I-·

4

D*

M*

u•

D M u 4

5 NL*

E*

N'

V'

E N v 5

6

F*

0*

W*

F 0 w 6

7

G*

P*

X*

G p x 7

8

H*

Q*

Y*

H Q y B

9 I*

R*

Z* I R z 9

A ¢ I :

B $ ' H

c < * %

(<i)

D ( ) '

-

E I ; >

-·

F I

---.

? "

Legend:

Examples:

*Codes

(in

addition

to

undefined

codes)

not

assigned

by

the

alphameric

keyboard

SP

-

Space

NUI. -

Null

NL -

New

Line

Note:

Charact~r

code

assignments

other

than

those

shown

within

the

heavily

outlined

portions

of

the

chart

above

are

undefined.

If

an

undefined

character

code

is

programmed,

the

character

that

will

be

displayed

is

not

specified.

The

character

displayed

by

the

2250

Model

3 for o

given

undefined

character

code

mny

be

different

for

other

device~.

IBM

reserves

the

right

to

change

at

any

time

the

character

displayed

by thP

2250

for

an

undefined

character

code.

Figure

6.

Character

Set

and

Code

Assignments

supplying a

constant

X and Y analog

voltage

to

the

main

deflection

yoke.

At

the

same

time,

the

char-

acter

deflection

system

forms

a

character

by

moving

the

beam

at

high

speed

between

various

addressed

points

in

the

character

grid

area.

Figure

8

illus-

trates

the

strokes

used

to

form

the

character

"A"

and shows

the

character

sizes

in

inches.

Table

1

lists

the

characteristics

of

a

character

display.

Character

spacing

(Figure

9)

is

an

auto-

matic

function

of

the

2250.

After

each

character

is

formed,

the

main

deflection

system

automatically

moves

the

electron

beam

in

the

+X

direction

to

the

new

character

area

center

point.

The

beam

is

moved a

distance

of 14

raster

units

(when

displaying

basic-size

characters)

or

21

raster

units

(when

dis-

playing

large-size

characters).

The

program

can

initiate

additional

spaces

of

14

or

21

raster

units

each

by

specifying

space

characters

to

the

2840.

Character

Byte

Code

Bl

or

Cl

F9

A

9

%

6C

NUL

00

Table

1.

Character

Display

Characteristics

Character

Size

Basic

Large

Characters

per

line

(max.)

74

49

Lines

per

display

(max.)

52

35

Number

of

characters

on

display

(max.)

3,848

1,

715

Character

spacing

(raster

units)

14

21

Line

spacing

(raster

units)

20

30

Hence,

one

space

character

results

in

a

distance

of

28

or

42

raster

units

between

the

center

point

of

the

previously

specified

character

area

and

the

center

point

of

the

area.

The

null

character

does

not

cause

a

display

and

does

not

affect

char-

acter-spacing

circuitry.

2250

Operations

11

,•

I

;

111

110

101

100

011

010

001

large

000

Figure

7.

111

001

last

0512 -? Graphic

1 Coordinate

I

0205

I

-r

I

-r

I

Basic

OIO

011

OIO

011 100

101

110

Character

Grid

Coordinate

System

111

last

Graphic

Coordinate

Line

spacing

is

initiated

either

by

the

program

or

by

the

2250.

The

program

initiates

a

line

space

by

specifying

a new

line

(NL)

character

to

the

2840.

The

2840,

in

turn,

decodes

the

character

and

sends

resulting

signals

to

the

2250

main

deflection

section,

which

repositions

the

electron

beam

to

the

first

char-

acter

area

center

point

of

a

new

line.

The

new

line

is

20

or

30

raster

units

below

the

de-

pending

on

the

character

size;

the

first

character

area

center

point

of a new

line

is

always

at

X =0000.

Successive

NL

characters

cause

successive

lines

to

be

stepped.

If

an

NL

code

is

not

specified,

the

2250

displays

characters

to

the

end of a

line,

automatically

steps

to

a new

line,

and

continues

the

display.

The

2250

performs

automatic

line

spacing

whenever

the

last

character

formed

is

so

near

the

right

boundary

of

the

display

area

that

character

spacing

cannot

be

12

completed.

This

occurs

when

the

center

point of

the

last

character

formed

is

to

the

right

of

X =

1,

009

(basic

size)

or

X =

1,002

(large

size).

The

2250

automatically

positions

the

beam

for

a

new

line

at

the

top

of

the

display

area

(X =0000,

Y =1023)

only

when

the

last

line

is

so

near

the

lower

boundary

that

line

spacing

cannot

be

completed.

This

occurs

when

the

line

is

below Y =0,0

20

(basic

size)

or

Y =

0,

030

(large

size)

•

LIGHT

PEN

The

light

pen

is

a

fiber-optic

pen-like

device

(Figure

10).

The

user

communicates

with

the

computer

or

the

2840-2

by

pointing

the

light

pen

at

the

section

of

the

displayed

image

(character,

vector,

or

point)

that

he

wants

to

identify

to

the

program.

When

the

light

pen

is

in

the

desired

position,

the

user

presses

the

pen

tip

against

the

CRT

faceplate

to

activate

the

tip

switch,

enabling

light-pen

operation.

The

light

pen

detects

light

from

the

CRT

beam

when

the

beam

passes

within

the

field

of

view

of

the

pen.

One

de-

tect

can

occur

for

each

activation

of

the

switch.

Subsequent

action

is

determined

by

the

buffer

pro-

gram.

This

action

could

be

an

interrupt

of

the

CPU

program

or

a

logical

buffer

action

such

as

transfer

to

a new

buffer

address,

store

X,

Y

registers,

etc.

The

buffer

program

can

also

cause

the

light-pen

switch

to

be

bypassed

so

that

the

switch

open/closed

condition

will

not

affect

light-pen

detects.

When

the

light

pen

is

continually

activated

by

the

program,

a

detect

can

occur

each

time

the

unblanked

beam

passes

within

the

field

of

view

of

the

light

pen.

This

"con-

tinuous

detects"

mode

of

operation

can

be

used

in

graphic

design

operations

such

as

light-pen

tracking.

In

addition,

the

buffer

program

can

disable

the

light

pen

as

certain

information

is

being

displayed,

in-

hibiting

light-pen

detects

on

that

information.

ALPHAMERIC KEYBOARD

This

feature

provides

a

typewriter-like

keyboard

from

which

the

user

can

compose

and/or

modify

messages

on

the

CRT

display

area.

Message

areas

on

the

display

can

be

protected

from

keyboard

action

by

the

program.

A

dash-like

mark,

called

a

cursor,

is

displayed

beneath

a

character

or

character

position

to

indicate

(to

the

user)

where

a

character

can

be

modified

or

inserted

by

keyboard

action.

For

ex-

ample,

whena

cursor

is

displayed

under

one

charac-

ter

in

a

line

of

characters,

that

character

can

be

changed

or

blanked

by

keyboard

action.

Also,

if

a

cursor

is

displayed

under

a

position

without a

character,

a

character

can

be

inserted

in

that

position

by

key-

board

action.

A

cursor

can

also

appear

beneath

a

protected

character

position;

however,

that

posi-

tion

cannot

be

used

for

character

insertion

or

mod-

ification

from

the

keyboard.

110

--------·-

Basic:

0.

103"

(Nominal)

Lor9~:

0.

155"

(Nominal)

I I

I

I I

-1---1---

1 I

I

I I

+---i---

---i---1

I I

101

I

I 1

I

Basic:

0.

16"

(Nominal)

100

Large:

0.

24"

(Nominal)

--,---

011

1

I

;-

--

1

I

--+--....

: I

1\

I I

"'{

I

1,

I I I

-...........1

I \

-

l---i---

-1---~~

I I I I

~

I i I I

I I I I

000

._

_ __.

__

_,_

__

_._

__

__._

__

,___~"""'"'-""-"'""'

~Automatic

Character

Space

000

001

010

011

100

Notes:

1 .

Deflection

AB

is a

function

of

entering

character

mode;

upon

leaving

character

mode,

the

beam is

repositioned

to

point

A

of

the

grid.

2.

Circled

numbers

refer

to

the

sequence

in

which

the

deflection

end

points

ore

addressed.

Figure

8.

Strokes

That

Form

the

Letter

"A"

Basic

~i

ze

Lorge

Size

101

~~""8

'~·"'a

Space

I

Space

I

•

14

RU

• I •

21

RU

• I

I I

Line

line

10

RU

Space

30

RU

Space

.,.

I :

• I • I

l 1

Figure

9.

Character

and

Line

Spaces

110

111

As

messages

are

being

composed

or

altered

by

the

alphameric

keyboard,

the

changes

are

inserted

in

the

displayed

data

during

the

normal

display

regeneration

cycle.

This

allows

the

user

to

verify

the

message

and

make

corrections

as

necessary.

The

user

in-

dicates

end

of

message

by

depressing

the

ALT and

END

keys

, which

generate

both

an

interrupt

to

the

CPU and

data

for

program

interpretation

and

action.

The

keyboard

(Figure

11)

contains

44

keys

and a

space

bar,

which

provide

a

selection

of

63

standard

characters.

Alphabetic

keys

compose

upper-case

characters

regardless

of

the

status

of

the

shift

key.

In

addition

to

the

standard

character

keys,

the

fol-

lowing function

keys

are

provided:

ALT: When

depressed

with

the

SHIFT

key

re-

leased,

allows

selection

of

the

Null,

End,

or

Cancel

2250

Operations

13

Figure

10.

Fiber

Optic

Light

Pen

Figure

11.

Alphameric

Keyboard

14

function.

When

depressed

with

the

SHIFT

key,

un-

locks

the

keyboard.

SHIFT: When

depressed,

allows

selection

of

the

upper

character

by

dual-character

keys.

When

released,

the

lower

character

can

be

selected.

The

SHIFT

key

must

be

released

when

using

the

End,

Cancel,

or

Null

function.

When

depressed

with

the

ALT

key,

unlocks

the

keyboard.

LOCK:

While

depressed,

locks

the

SHIFT

key

in

the

depressed

position.

END:

Causes

a

CPU

interrupt.

It

informs

the

program

that

a

manual

alphameric

keyboard

opera-

tion

is

completed.

CANCEL:

Causes

a

CPU

interrupt.

The

function

of

this

key

is

determined

by

the

application

program;

one

possible

function

might

be

to

provide

the

user

with

a

method

of

requesting

a

program

subroutine.

JUMP:

Moves

the

cursor

in

the

forward

direction

from

its

current

position

to

the

first

character

posi-

tion

of

the

character

area.

This

area

may

be

before

the

cursor

starting

position

if

all

positions

following

the

cursor

starting

position

are

protected.

If

the

cursor

is

in

a

protected

char-

acter

area,

and

if

the

display

does

not

have

an

un-

protected

area

(this

is

a

programming

error),

depressing

the

JUMP

key

initiates

a

continuous

search

by

the

2840

for

an

unprotected

area.

The

display

continues

to

cycle

during

this

search;

how-

ever,

it

cannot

be

changed

or

stopped

by

the

channel

program.

Recovery

can

be

made

by

disabling

the

2250

or

by

a

reset

at

the

CPU.

ADVANCE:

Advances

the

cursor

one

character

position

without

changing

the

characters

displayed.

I~

the

cursor

is

under

the

last

character

position

of

the

unprotected

area,

it

will

not

advance.

BACKSPACE:

Backspaces

the

cursor

one

char-

acter

position

without

changing

the

characters

dis-

played.

If

the

cursor

is

under

the

first

character

position

of

the

character

area,

the

cursor

will

not

backspace.

CONTINUOUS: Allows

continuous

automatic

operation

of

an

ADVANCE,

BACKSPACE,

SPACE,

NULL,

alphameric,

or

special

character

key

at

the

rate

of

the

regeneration

cycle.

The

cursor

symbol

is

displayed

under

the

char-

acter

position

at

which

the

character

selected

by

the

user

at

the

alphameric

keyboard

will

be

placed.

The

user

can

move

the

cursor

to

any

desired

position

within

a

protected

or

unprotected

area

into

the

area

only

by

the

JUMP

key

or

by

the

program.

A

cursor

must

be

inserted

by

the

program

if

keyboard

operations

are

required.

If

the

cursor

is

in

a

protected

character

area,

it

must

be

moved

to

an

unprotected

area

by

the

JUMP

key

before

the

character

keys

become

effective.

Cursor

operation

in

a

protected

area

is

the

same

as

in

an

unprotected

area

except

that

a

character

cannot

be

inserted

or

changed

from

the

keyboard.

When

the

cursor

is

inserted

by

the

program

into

a

buffer

location

that

contains

a

null,

the

cursor

is

not

displayed.

The

program

must

not

insert

a

cursor

into

a new

line

(NL)

position.

If

the

user

attempts

to

insert

a

character

into

a

position

where

the

character

is

actually

a

null

character,

the

character

will

be

inserted

in

the

position

containing

the

cursor,

and

all

other

characters

to

the

right

of

the

null

will

be

shifted

one

character

space

to

the

right

to

make

room

for

the

new

character.

This

shifting

may

cause

automatic

linespacing

(if

the

last

character

in

the

line

should

be

sufficiently

to

the

right

side

of

the

display

area

so

that

the

shift

causes

it

to

start

a

new

line).

The

cursor

will

skip

over

the

NL

character

when

it

is

encountered

as

a

result

of

each

keyboard

action.

The

NL

character

must

not

be

either

the

first

or

the

last

character

in

a

Character

mode.

As

each

character

position

is

used

by

the

key-

board,

the

cursor

is

automatically

displayed

at

the

character

position

until

it

is

in

the

last

character

position

of

the

unprotected

area.

When

this

occurs,

the

cursor

remains

assigned

to

the

last

position

until

repositioned

by

the

program

orbytheJUMPor

BACKSPACE

key.

Whena

cursor

isnotinthebuffer,

theJUMP,

ADVANCE

and

BACK-

SPACE

keys

are

inactive,

and

keyboard

lockup

will

not

occur.

PROGRAMMED FUNCTION KEYBOARD

The

programmed

function

keyboard

(Figure

12)

con-

tains

32

keys,

32

indicators,

and

eight

switches

to

sense

the

code

punched

into

the

overlay.

The

appli-

cation

program

defines

the

function

of

each

key

and

indicator.

Each

of

256

possible

overlays

identifies

the

function

of

the

keys

and

indicators,

both

to

the

operator

and

to

the

CPU

program.

Each

key

can

initiate

a

subroutine

associated

with

the

respective

overlay

program.

When a

key

is

pressed,

the

keyboard

is

electrically

locked

(keys

can

be

pressed,

but

they

will

have

no

effect).

The

overlay

sensing

switch

configuration

is

sent

to

the

program

with

each

key

code,

thereby

identifying

the

overlay

being

used.

The

program

then

acts

on

the

displayed

image

as

directed

by

the

program

subroutine

associated

with

the

key

and

overlay

codes.

For

example,

the

sub-

routine

might

direct

the

2250

to

enlarge,

reduce,

or

delete

the

displayed

images.

Plastic

overlays

(PN 5704496)

are

available

directly

from

the

DP

Administration

Operations

Office

(AOO). One

overlay

punch

(PN 5704549)

per

installation

is

furnished

to

each

customer

at

no

charge.

Additional

punches

can

be

ordered

on

an

MES

from

IBM

Kingston.

2250

Operations

15

16

Figure

12 .

Programmed

Function

Keyboard

Each

of

the

32

programmed

function

keyboard

keys

has

a

built-in

indicator.

Operation

of

these

indicators

is

independent

of

the

operation

of

the

Overlay

Sensing

Switches

keys;

however,

the

indicators

can

be

used

for

asso-

ciated

functions

such

as

informing

the

operator

of

keys

that

can

be,

or

have

been,

activated

.

Operations

performed

by

2250 Model 3

Display

Units

are

controlled

by

a 2840 Model 2

Display

Control.

All

attached

22501s

share

the

2840

buffer

(Figure

13),

which

is

used

for

display

regeneration.

A

buffer

program

comprising

image

data

bytes

and

associated

control

bytes

is

received

from

the

channel

and

placed

into

the

buffer

under

channel

program

control.

These

bytes

are

then

used

by

the

2840

to

maintain

display

regeneration

simultaneously

for

the

associated

2250'

s.

This

process

frees

the

channel and

the

CPU

for

other

operations

during

display

regeneration.

The

basic

2840

buffer

can

store

up

to

32,768

bytes

of

information.

The

byte

storage

locations

are

as-

signed

sequential

permanent

addresses,

0

through

32,

767.

During

display

operations,

bytes

are

retrieved

from

the

buffer

in

pairs,

as

needed

by

the

attached

2250's:

one

from

an

even-numbered

address

and one

from

the

ne:x-t

sequential

odd-numbered

ad-

dress.

(Wrap-around

will

occur

in

this

buffer

if

the

last

two

bytes

are

not

occupied

by

a

Transfer

order.)

Maximum

time

to

retrieve

a

byte

pair

from

the

buffer

during

display

operations

is

2.

0

µs,

a

maximum

effective

data

rate

of

1.

0 µs

per

byte.

The

buffer

area

(block of

buffer

locations)

used

with

each

2250

is

assigned

in

the

buffer

program.

Two

or

more

22501s

can

display

the

same

image

from

the

same

buffer

area,

or

each

2250

can

display

from

different

buffer

areas.

The

size

of

each

assigned

buffer

area

is

determined

by

the

buffer

program

and

is,

therefore,

variable.

An

address

register

asso-

ciated

with

each

2250

specifies

the

buffer

location

at

which

data

for

that

2250

will

be

stored

or

from

which

it

will

be

retrieved.

These

address

registers

are

loaded

initially

by

the

CPU

program;

they

can

then

be

automatically

stepped

by

buffer

addressing

cir-

cuitry,

altered

by

buffer

control

circuitry,

or

re-

loaded

by

a channel

program.

ORDERS

The

buffer

program

consists

of

orders

interleaved

with

data.

Orders

are

interpreted

by

the

2840

as

re-

quests

to

perform

logical

operations

such

as

uncon-

ditional

transfers

or

requests

to

decode

subsequent

data

in

any one of

the

available

data

modes

(e.g.,

Point

Plot,

Large

Character,

etc.).

The

data

bytes

following

each

order

contain

information

necessary

to

define

points,

vectors

,

or

characters.

Display

layout

sheets

(Form

No. X27-2950), which

can

be

ordered

through

the

local

IBM

branch

office,

aid

in

the

planning

and

programming

of

display

patterns.

2840 OPERATIONS WITH ATTACHED

2250's

Order

Format

An

order

is

composed

of

two,

four,

or

six

consec-

utive

bytes.

The

first

two

bytes

are

always

the

set

mode

(SM)

byte

and a

mode

control

(MC)

byte.

The

SM

byte

contains

a fixed code

(hexadecimal

2A)

that

marks

the

beginning

of

a new

order.

The

MC

byte

contains

a

variable

code.

Because

a

variable

num-

ber

of

associated

data

bytes

can

immediately

follow

an

order,

the

unique

SM

byte

is

provided

to

allow

2840

circuitry

to

detect

the

presence

of

a new

order.

The

SM

byte

must

always

be

located

at

an

even-

numbered

buffer

address,

and

the

MC

byte

must

immediately

follow

the

SM

byte.

The

SM

byte

resets,

modifies,

or

clears

the

pre-

sent

mode of

operation,

and

the

associated

MC

byte

defines

the

new

mode

of

operation.

The

display

unit

remains

in

the

new

mode

until

another

order

is

re-

ceived

from

the

buffer

and

is

executed.

Once

an

order

to

enter

a

mode

has

been

executed,

each

even-

address

byte

thereafter

is

checked

to

determine

whether

it

contains

the

SM

code (indicating

the

start

of a new

order).

When a

four-

or

six-byte

order

(such

as

Transfer

or

Move

Immediate

Address)

is

executed,

only

the

first

even

byte

is

checked

for

an

SM

code;

each

even

byte

after

the

complete

order

is

checked

as

in

other

modes.

If

an undefined

order

is

decoded,

the

existing

mode

is

reset,

and

the

order

is

processed

as

a

2-Byte

No-Op.

The

2840

then

continues

by

checking

each

even

byte

for

an

SM

code.

Orders

used

in

the

2840

are

divided

into

four

groups,

or

modes:

Graphic,

Character,

Control,

and Light

Pen.

The

orders

in

each

mode

are

listed

in

Table

2.

They

are

also

described,

by

mode,

in

the

following

paragraphs.

Both

the

SM

and

MC

bytes

are

coded

in

hexadecimal,

which

is

described

in

Appendix A.

Graphic Mode

Orders

Graphic

mode

orders

are

used

for

point

and

vector

plotting and

for

electron

beam

positioning.

These

orders

are

normally

followed

in

a

buffer

program

by

data

bytes;

they

are

sent

by

the

2840

to

the

2250

associated

with

the

buffer

program.

In

either

Graphic

mode

(Absolute

or

Incremental)

,

data

is

transferred

from

the

data

register

to

the

associated

2250.

It

is

transferred

from

the

buffer

to

the

data

registers

as

needed

by

the

individual 2250

's.

2840

Operations

with

Attached

2250

1s

17

2840

2250

No.l

Channel

Interface

Control

~

A

11

attached

2250

's

I I I I

Audible

Alarm

I I I

I

•

I

l

'-

-

r.J---

1 Programmed

I

Function

I

Keyboard

I

L

___

_J

Address

Reg

l

Data

Reg

l

2250 No.1

I I I I

I ; : I

r

._

__

-,

I

Alphameric

I

I Keyboard I

L----...l

Notes:

Figure

13.

Functional

Sections

of

the

2840-2

and

a

2250-3

18

Address

Reg

2

Data

Reg

2

Addressing

Buffer

Register

Character

Generator

--,

Data

I

_

_J

'------.r---'

r-----,

I Address I

I

Reg

4 I

__

_J

r--

--,

I

Data

I

Reg

4 I

L_

__J

Operator's

Panel

.____,_,'---.,-J~

2250

No.2

2250

No.3

2250

No.4

2250

Character

Stroke

Deflection

Intensity

Control

Assembly

Main

Deflection

l.

Dashed

blocks

represent

special

feature

functions.

2.

Heavy

lines

represent

data

flow.

II

2250

Control

Various

I

...

_J

Operator's

Panel

No.2

No.3,4

Light

Pen

Table

2.

Mode

Orders

Mode

Orders

Graphic

Enter

Graphic

Mode,

Absolute

Point

Plotting

Enter

Graphic

Mode,

Absolute

Vector

Enter

Point

Plot

Incre-

mental,

2 Byte

Mode

Enter

Vector

Plot

Incre-

mental,

2 Byte

Mode

Character

Enter

Character

Mode

Fixed,

Basic Size

(un-

protected)

Enter

Character

Mode

Fixed,

Large

Size

(un-

protected)

Enter

Character

Mode

Protected,

Basic Size

Enter

Character

Mode

Protected,

Large

Size

Control

Enter

2-Byte

No-Op

End

Order

Sequence

2-Byte

Class

Start

Regeneration

Timer

Enter

4-Byte

No-Op

Transfer

Uncondi-

tional

4-Byte

Class

Store

X,

Y

Deflection

Registers

in

Buffer

Move

Immediate

Ad-

dre•

I'--

Class

Move

Immediate

Data

Light

Pen

Defer

Response

to

"

Light-Pen

Detects

Enable

Switch

Detect

Operation

2-Byte

Disable

Light-Pen

Class

Detects

Enable

No

Switch

Detects

Operation

Permit

Detect

lnterru

pt

Transfer

on

Deferred

°""'""

1

·--

Class

Transfer

on

No

Detect

Mnemonic(!)

SM

GEPM (A) (ABS)

2A

GEVM (A) (ABS) 2A

GEIP2 2A

GEVI2

2A

GECF (B) (BASIC) 2A

GECF (L) (LARGE) 2A

GECP (B) (BASIC) 2A

GECP (L) (LARGE) 2A

GNOP2

2A

GEOS

2A

GSRT

2A

GNOP4 2A

GTRU

(ADDR) 2A

GSXY (ADDR) 2A

GMVA (ADDR, LOC) 2A

GMVD (ADDR, LOC) 2A

GDRD 2A

GESD 2A

GDPD 2A

GENSD 2A

GPDI 2A

GTDD(ADDR)

2A

GTND

(ADDR) 2A

MC

00

02

04

05

40(2)

41(3)

44

45

80

81

82

co

FF

EA

EB

EC

83

84

85

86

87

FC

FD

NOTES:

1.

Parameters

are

shown

after

various

mnemon-

ics;

parentheses

indicate

optional

parameters

(any

one

of

the

parenthesized

parameters

after

the

mnemonic

can

be

used) •

The

mnemonics

shown

are

those

used

by

IBM

Type

I

Programming

Support

Packages.

2.

An

MC

code

of

50

or

52

can

also

be

used:

GECV

(B)

(BASIC) (S) (SMALL).

3,

An

MC

code

of

51

can

also

be

used:

GECV

(L)

(LARGE).

2840

Operations

with

Attached

2250

1s

19

Absolute

Graphic

Orders

(GEPM and GEVM)

N,

N+l

N+2,

N+3

N+4,

N+5

0

2A

B 0

0 0

1

00 (Point Plot)

02 (Vector Plot)

0 X Position

0 Y

1Position

0 l 2 3 4 7 8

15

Two

orders,

Enter

Graphic

Mode Absolute

Point

Plotting

and

Enter

Graphic

Mode Absolute

Vector,

provide

the

capability

of

displaying

a

graphic

image

by

addressing

the

actual

reference

grid

coordinates

to

which

the

electron

beam

is

to

move.

Each

group

of

four

absolute

data

bytes

identifies

one

beam

de-

flection

end

point.

A

vector

or

point

is

displayed

when

the

blanking

bit

(B)

is

O,

and

the

beam

is

positioned

without

caus-

ing

a

display

when

the

blanking

bit

is

1.

An

isolated

line

drawn

between

two

arbitrary

points

requires

a

vector

with

a 1

blanking

bit

(no display) followed

by

a

vector

with

a 0

blanking

bit

(drawing

the

line).

For

improved

image

accuracy

on

complete

images

that

are

displayed

in

less

than

25

ms,

the

beam

should

be

returned

to

the

center

of

the

display

area

(X

=

512,

Y = 512)

after

the

image

is

displayed.

Incremental

Graphic

Orders

(GEPI2 and GEVI2)

N,

N+l

2A

04 (Point Plot)

05

(Vector Plot)

N+2,

N+3 S X

lncremental(t.

X) S Y Incremental( t. Y) B

0 6 7 8 9

14

15

Two

orders,

Enter

Point

Plot

Incremental

Two Byte

Mode and

Enter

Vector

Plot

Incremental

Two Byte

Mode,

provide

the

capability

of

displaying

a

graphic

image

by

specifying

incremental

displacement

from

an

absolute

beam

position.

A

maximum

displacement

of +63

or

-64

raster

units

can

be

specified

for

X and

for

Y.

Each

displacement

value

can

be

positive

or

negative.

When

negative,

the

data

is

presented

in

two's

complement

form

(see

Glossary).

The

incre-

mental

X and Y

values

are

added

to

the

absolute

X

and Y

values

(the

current

beam

position),

providing

a new

absolute

value

for

the

new

beam

position.

The

two

S-bits

in

each

pair

of

incremental

data

bytes

define

the

signs

of

the

X and Y

increments.

A

0

sign

bit

signifies

a

positive

number,

whereas

a 1

20

sign

bit

signifies

a

negative

number

in

two's

com-

plement

form.

The

blanking

(B)

bit

associated

with

the

new

absolute

value

is

a 0 when a

point

or

vector

is

to

be

displayed.

When

the

B-bit

is

a

1,

indicating

a

blank

vector,

the

beam

is

not

intensified

as

it

is

moved

to

the

new

position.

Note

that

bit

7

of

the

even

data

byte

must

alw~ys

be

a 1

so

that

the

data

cannot

be

interpreted

a~

a

set

mode

code.

Vector

or

point

defl¢ctions

in

the

Incremental

mode

start

at

the

current

beam

position

and end

at

an

X,

Y

position

determined

as

follows:

X

new=

X

current±

AX

Y new = Y

current

± AY

a

string

of

incremental

vectors

or

points

can

be

moved about

the

screen

without

affecting

their

length

or

orientation

by

modifying

the

starting

position

of

the

first

vector

or

point

in

the

string.

In

the

two-byte

Incremental

mode,

each

X and Y

displacement

of

the

beam

falls

into

the

range

O

to

+63

or

-64

raster

units

(0

to

0.

74 inch) • When

the

X

or

Y

increment

causes

the

beam

to

move

outside

the

1,024

raster

unit

image

area,

the

point

or

entire

vector

will

be

blanked,

as

will

all

subsequent

dis-

play

data

until

the

beam

is

returned

to

the

usable

image

area.

The

beam

can

be

returned

in

either

of two

ways:

by

incremental

movement

in

the

opposite

direction,

or

by

displaying

any

absolute

point

or

vector.

If

the

first

absolute

data

bytes

received

by

the

2250

after

the

beam

is

returned

specify

an

unblanked

vector,

a

line

will

be

drawn

from

a

wrap-around

position

to

the

specified

location.

Character

Mode

Orders

(GECF

Basic

or

Large

and

GECP

Basic

or

Large)

40 (Fixed Basic Size)

N,

N+l

2A

41

(Fixed Large

Size)

44

(Protected

Basic Size)

45

(Protected

Large Size)

N+2,

N+3 l

Char.

1

Char.

6 7 8

15

Each

Character

mode

order

(1)

prepares

the

2840

to

operate

with

character

data

bytes

,

(2)

specifies

whether

these

bytes

are

to

be

protected

against

manual

alteration,

and

(3)

prepares

the

2250

to

dis-

play

standard

characters

in

the

specified

size.

Character

data

bytes

are

stored

in

sequential

buffer

locations

following

the

order.

Each

data

byte

con-

tains

the

code

of

an

alphameric

or

control

character

from

the

standard

character

set

(Figure

6).

For

(

\

IBM 2250 3 User manual

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