Tektronix 4954 Instruction Manual

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4953/4954

GRAPHICS

TABLET

INSTRUCTION

MANUAL

Tektronix,

Inc.

P.O.

Box

500

Beaverton,

Oregon

97077

MANUAL

PART

NO.

First

Printing

FEB 1975

070-1791.01

•

Thl.PrintlnQ.JUN 1980

4953/4954

TABLE

OF CONTENTS

SECTION 1 DESCRIPTION

General

Graphics Tablet

Components

Tablet

Presence Area

Standard Accessories

Optional Accessories

Specifications

Page SECTION

4 SERVICING

(cent)

Page

1-1

COMSUP

Strap

Verification 4-5

1-2

Major

Component

Verification

4-5

1-2

Interconnecting

Signals

4-8

1-3

Tablet

Digitization 4-8

1-3

Block

Diagram Description

4-9

1-3

SECTION 2

OPERATION

Installation

Operation

Operating

Procedure

Header

Characters

Control

Commands

Terminal/Tablet

Interaction

Operating

Modes

Single Point/Pen
Single

Point/Presence

Multiple

Point/Pen

Multiple

Point/Presence

Graphic

Data

Input

2-1
2-1

2-1

2-2

2-2

2-3

2-5

2-5

2-6

2-8

2-9

2-10

SECTION

3

SUPPLEMENTAL

INFORMATION

3-1

AC

PoweT Requirements

AC

Power

Cord and Grounding

Requirements

Line Voltage

Selection

Fuses

Strappable

Options

Biasing

the

Tablet

SECTION

4 SERVICING

Introduction

Equipment

Required

Performance

Checks

Miscellaneous

Circuit

Verifications

Delay

Verification

Bit

1 Verification

Bit

2 Verification

Bit

3

Verification

Bit

4

Verification

Bit

5

Verification

CR Strap Verification

ESUP

Strap

Verification

HEADER

Strap

Verification

Crosshair

Operation

Verification

3-1

3-2

3-2

3-2

3-4

4-1
4-1

4-1

4-1

4-2

4-2

4-3

4-3

4-3

4-3

4-4

4-4
4-4

4-5

SECTION

5 CIRCUIT

DESCRIPTIONS

Tablet

Control Card

5-1

Tablet

Clock

5-1

Divide-by-four

5-1

Sync

5-1

Tablet

Sequencer

5-1

Wait

One-Shot

5-1

X-Counter

5-1

Y-Counter

5-2

Digital Delay

5-2

Address

Decoder

5-2

Transmit Enable

5-2

ESUP

5-2

Transmit

Initiate

5-2

Output Sequencer

5-3

Character Identifier

5-3

Output

Shift Register

5-3

Presence

Latch/True

Presence

5-4

Pen

Status

5-4

Header

Control

5-4

Crosshair

5-4

Pen

Mode

5-4

Comsup

5-4

Enq

Generator

5-5

Presence

Status

5-5

Control

Board

5-5

Line

Filter

5-5

Line

Voltage

Strapping

5-5

Power-On

Relay

5-5

180 V

Supply

5-5

4-5

V

Regulator

5-5

Buffer

Amplifier

5-6

SECTION

6 ELECTRICAL

PARTS LIST

6-1

SECTION

7 DIAGRAMS

7-1

SECTION

8 MECHANICAL PARTS

LIST

8-1

CHANGE

INFORMATION

W

REV

A, FEB

1979

\

\

{

n—

_-—

-~+"

r

'~

^^^'

Yr:^:.

{

thk

-

.

-

\

K

< 1

Fig.

1-1.

4953

and

4954

Graphics

Tablets.

4953/4954

4953/4954

Section

1

DESCRIPTION

GENERAL

The

4953

and

4954

Graphics

Tablets

(Fig.

1-1)

input

graphic

data

to

a

computer,

through

a

TEKTRONIX

401

0-

Series

Graphic

Display

Terminal.

The

devices

are

iden-

tical

except

for

the

size

of

the

tablets;

the

4953

is

an

11

inches

by

11 inches

tablet,

while

the

4954

is

40

inches

by

30

inches.

Cleaning

agents that

contain

hydrocarbons

will

dissolve

the

tablet

surface.

The

polystyrene

surface

will

react,

similarly

to

most

petroleum

derivatives.

Safe

cleaning

agents are

alcohols—

ethyl, methyl,

isopropyl—or

soaps

and

detergeMs

that

do not

contain

hydrocarbons.

The

basic

function

of

the

Graphics

Tablet is to

convert

the

position

of

the

pen on

the tablet

surface

to

a

corresponding

digital

position that

is in usableform

forthe

4010-Series

Computer

Display

Terminal.

The digital

posi-

tion

may

be simultaneously

transmitted to the

terminal

and

computer,

or it may

be transmitted

to

the

computer

through the

terminal

bus alone,

with

no local

copy

of the

transmission

appearing

on

the

terminal

display.

The

position

of

the

Graphics

Tablet in

a computer/terminal

system

is

shown

in

Fig,

1-2.

The

4010-family

terminal

can

operate

in a

mode termed

Graphic

Input

(GIN),

in which

identifiable

points

are

digitized

and

sent

to

the

computer.The

Graphics

Tablet

extends

the

terminal's

ability

to input

this type

of

graphic

information,

inputting

points

continuously

or

one

at

a

time,

in

a

mode

similar

to

the

terminal's

Graphic

Input

mode.

Input

is

accomplished

by first

enabling

the

tablet

with

a

three-character

command

string,

and

then positioning

the

pen

along

the

surface

of the

tablet

area.

Data input

may be

Continuous

or one

point

at a time,

ft

may

be dependent

on

pen

proximity

only

oronthe

condition

of the

pen-switch,

and

local

display

(on the

screen

of the

4010-series

terminal)

may

be

selected

on or

off.

In

addition,

each

coordinate

value (X

and

Y) may

be

defined

by 10

bits of

data

or

12

bits

of data.

Ail

of

the

above variables

are

determined

by the

third

character

in the

command

string,

as

explained

in the

Operation

Section.

4953/4954

:

GRAPHIC TABLET

:

;?X~rv^ss#y>,z

}

^

1791-02

;

Fig.

1-2.

Graphics

Tablet

position

in a system.

REV.

A, AUG.

1977

1-1

Description—

4953/4954

The

Graphics

Tablet

functions

as

an

integral

part of the

terminal

hardware by

means

Of

an interface

card

con-

nected

to

the

terminal

minibus. The

minibus

is

the

terminal's

main data

routing

avenue. Any

device

con-

nected to

the

terminal

minibus

can respond to

the

Tablet

data

sent

through

that

minibus.

This allows

the

operator

to

format

Graphics

Tablet

data off-line from

a computer,

and

then

send

that

data to

the computer when

the

desired

graphic

input

has been

obtained.

GRAPHICS

TABLET

COMPONENTS

The

four

main components

of the

Graphics

Tablet

are

the

writing surface

(Tablet),

the Writing

Pen, the

Power

Module, and

the

Tablet

Control Card

which plugs

directly

into

the

minibus of

the

4010-Series Computer

Display

Terminal.

Tablet.

The tablet is a

flat writing

surface,

magnetically

prebiased, on

which

paper

(film,

etc.) maybe

placed

and

then

traced to

input

data

to

the computer.

Under

the

surface

of the

tablet are

two

grids of

magneto-strictive

wires, one

set for the

X axis and

one set for

the

Y

axis.

An

acoustic

wave

is

sent

along

these

wires and

detected

by

the

writing

pen; the

time

-between when the wave

is sent

and

when it

is

received

allows

identification

of data

points

in

a grid

of 1024

X

points by

1024 Y points.

Identifiable

points

are 0.01 inch

apart.

The

4954

maintains

0.01 inch

resolution

by

operating

with

12

bits

of graphic

data

per

point,

or

3840 by 3072

points-

Point

identification

can be

more

clearly

understood

if

one

thinks

of

the writing

surface

as containing

1024

vertical

lines and

1024

horizontal

lines.

An

identifiable

location on

the

writing

surface

can

be

established

at

the

intersection

of

any

vertical

and

horizontal line.

These

identifiable

locations

directly

correspond

to

the

iden-

tifiable points

of the

terminal's

display

screen.

In

the

optional

accessory

cursor,

the

switch

function

is

performed

by

the

button

on

top

of

the

cursor.

Power

Module.

The

Power

Module

contains

the

power

supply,

the

tablet

pulser

and

preamp,

and

the

connections

which

tie

the

Graphics

Tablet

components

together.

In

addition,

the

Power

Module's

front

panel

contains

the

Power

Switch

and

Indicators,

The

Indicators

provide

the

following

information:

Indicators

READY-"On"

indicates

that

the

Tablet

is

ready

to

send

another

point.

PEN—

illuminates

when

pen

pressure

is

applied.

DATA—

Illuminates

when

data

is in

the

process

of

being

transferred.

POWER—

Illuminates

when

Power

is

applied

to

both

the

Graphic

Tablet

and

the

terminal.

Tablet

Control

Card.

The

Tablet

Control

card

contains

those

circuits

necessary

to

convert

the

pen

signal

to

its

digital

equivalent.

This

card

connects

directly

to

the

terminal

minibus,

and

contains

circuits

for

format

chang-

ing,

data

transfer,

"header

character"

data,

and

other

tablet-related

functions.

#

Writing

Pen. The

tip of

the

writing pen

contains

a

sensitive

pick-up coil

which,

when moved

into

the

presence

of

the

tablet,

detects the

change in

magnetic

field caused

by the acoustic

wave.

The

detected

signal

is

then

converted to

digital

information

that directly

relates

to

pen

position. Once the

specific

operating

mode

has

been

established, the

writing

pen provides

sufficient

control

to

handle all data

transfer (stop and

go functions)

to

the

terminal

and

computer.

An

optional

ballpoint

filler

may be

used

in place

of

the

dry

filler for the pen

f

so the

operator

can

draw

the

information he is

sending

to the

computer;

otherwise,

the

standard

inkless

filler

can

be

used.

The

pen

can be

replaced

by an

optional

accessory

"cursor"

if

greater

accuracy

is

required

(such

as

tracing

a

drawing).

A

pen switch is located

within

the pen, and

is

activated

by pressing

the pen tip against

the

tablet

surface,

pressing

the

filler slightly into the

pen.

TABLET

PRESENCE

AREA

The

Graphics

Tablet

responds

to

the

pen

(In

Presence)

whenever

the

pen

is

within

0.125

inch

of

the

surface

of

the

tablet

In

addition,

only

a

certain

portion

of

the

tablet

surface

represents

the

valid

data

area.

The

location

of

this

area

is

dependent

on

the

biasing

of

the

tablet,

but

the

size

is

standard

for

each

of

the

tablet

sizes.

On

the

4953,

this

area

is

10.24

inches

in

each

axis;

on the

4954,

this

area

is

38.4

inches

in

the

X-axis

by

30.72

inches

in

the

Y

axis.

This

area

is

not

marked

on

the

tablet

surface,

since

it

may

move

slightly

each

time

the

tablet

is

biased.

It

may

be

located

by

the

operator

by

enabling

the

tablet

with

an

ESC !

N,

so

that

the

tablet

disarms

when

the

presence

area

is

exceeded.

He

may

then

slowly

move

the

pen

to

the

border

of

the

tablet,

and

watch

to

see

when

the

READY

indicator

is

ex-

tinguished.

This

marks

one

presence

boundary

point.

This

point

may

be

marked

and

the

procedure

tepeated

to

find

the

complete

boundary.

An

example

is

shown

in

Fig.

1-3.

1-2

REV.

A,

JULY,

1975

. TEKTRONIX

'•

V

m p

m

^^^m

mxm

;

ft

Out

of

Display

Area

Presence

Boundary

Display

Area

•

.

;:,:-^;^

,

.;-.:.;:V'.

,

;

r;v;'V:v

;

1791-03

Fig.

1-3.

Tablet

presence area.

STANDARD

ACCESSORIES

The

following standard

accessories

are

included with

each

Graphics

Tablet.

Instruction

Manual

Reference

Card

Pen (with inkless

filler)

Biasing

Magnet

(4953)

Biasing

Magnet

(4954)

070-1791-00
070-1787-00

119-0621-00

119-0686-00

119-0687-00

STANDARD

ASSEMBLIES

Power Module

Interconnecting Cable

(Power Module

to

Tablet Control Card)

Tablet Control Card

Tablet

(4953

only)

Tablet

(4954

only)

620-0240-00

012-0568-00

670-3536-XX

119-0619-00

119-0620-02

Description—

4953/4954

SPECIFICATIONS

Power Specifications

The Graphic

Tablets operate

from any

of the

line

voltage ranges

shown

in

Table

1-1.

TABLE

1-1

Operating Voltage

Ranges

Voltage Frequency Tolerance

Range

104 Vac

48-440

Hz

±10%

94-114

Vac

115 Vac

104-126

Vac

208

V

ac

187-228

V

ac

240

V ac

216-264

V

ac

Tablet

Interface

Current

Requirements:

-15

V—at 80 mA, drawn from

terminal bus

+15 V—at 40

mA,

drawn from

terminal bus

180 V—at 10

mA, supplied by

the

tablet power

supply

+5

V—at 1.5

A, supplied by

the

tablet

power supply

Environmental

Specifications

Temperatures:

OPTIONAL

ACCESSORIES

Operating,

from

0°C

to

40°

C

Storage, from

—

30°C

to

40°

C

Humidity:

Storage to 95%

humidity

at 30°

C

Presence

Distance

Specification

With

the pen

or

cursor

within

0.1 25

inch

of

the

tablet

surface, the

data obtained will be

stable

with respect

to

the

steadiness of the physical

positioning

of

the

pen

orcursor.

Presence

Area

Specification

4953

10.24

inches

by

10.24

inches

4954

38.4

inches by

30.72

inches

The

following optional

accessories

are

available forthe

Graphics

Tablet, at

additional

cost.

•

Cursor

(replaces pen)

Software support

package

(with paper

tape)

(with

source card deck)

Pen

Fillers

Dry

Blue

119-0622-00

4010A0601

4010A06

D1

6-0335-00

016-0334-00

Tablet

Error

The

maximum error produced by

the

Graphics

Tablet

in

the digitizing procedure

is

defined

as

1/4

of a

least

significant

bit

per

inch, or

0.0025 inch

of

error

per inch

of

tablet surface.

This

translates to a

maximum

error

specification

as

follows:

4953

4954

±0.03

inch

over

entire

tablet

surface

±0.10

inch

over

entire

tablet

surface

REV

C.JUN

1979

1-3

4953/4954

Section

2

OPERATION

INSTALLATION

Installation

of

the Graphics

Tablet consists of

making

certain

the

unit

is

wired for

the available line voltage

and

connecting

to

a

power

source,

selecting Strappable

Options

to

fit user requirements,

connecting the Graphics

Tablet

components

together,

and installation of the

Tablet

Control

card into

the

terminal minibus. Line Voltage

Selection

and

Strappable

Options

are

covered under

separate

headings

within Section

3-

To

connect the

Graphics

Tablet components

.together,

proceed as

follows.

Connect

the cable from the

pen

to J1014 on the rear

panel of

the Power Module.

There

is a keying notch

on

the

top of the rear

panel connector, which

is

to align

with

the key

on the

tablet

cable

connector (Fig.

2-1).

2.

Connect the cable from

the pen to

J1016

on the

rear

panel of

the

Power

Module.

There is a keying

notch

on

this' -connector also, to

align

with the

key

on

the

pen

cable

connector (Fig.

2-1).

3. Connect the

25-pin

connector

on

the Tablet Control

card

interconnecting

cable

to J1010

on

the Power

Module rear

panel, and

secure

with

the

two attaching

screws

(Fig.

2-2).

To

Tablet

1791-04A

&!!&?

Fig.

2-1,

Pen and

Tablet e&nagsfion.

Fig.

2-2.

Tablet

Control

Card cable

connection.

A. Install

the

Tablet Control

card

into a

spare

slot in

the

terminal minibus.

Thread the

cable from

J1010

on

the

Power

Module

through

the

access

slot

on

the rear of

the

terminal

pedestal,

then

attach

the

two

harmonica

connectors

(P231

and P232)

to

their

positions on

the

Tablet Control

card

(Fig.

2-3).

(Make

certain

that

pin

1

of

each

connector

aligns

with

pin 1

of

the card

connectors;

they

are

marked

with

small carets,)

Connect

the

ground

lug to

the

ground

spades

under

the

card rack

within the

terminal

pedestal.

It

may

be

necessary

to

install a

Mother

Board

extender

in

the

terminal to

provide

room

for

the Tablet

Control

card.

Refer to the

terminal

manual for

details.

OPERATION

Operating

Procedure

Operation of

the

Graphics

Tablet

consists

of

enabling

one

of

the four

basic

Operating

Modes,

then

manipulating

the

pen on

the

tablet

surface.

The pen may

be

pressed a£,

REV

D.FEB

1979

2-1

Ope

ra

tio

n

—4953/4954

"

-

•--"-»-

"•-

~

-

,

,-.-

,-

,

-,„ ....

""•""""•"—•"''

'

*

-

.-

.

1791-06.1

Rg.

2-3.

Installing

ihe

Tablet

Control

Card.

necessary

to

input

coordinate

points.

An

Operating

Mode

is

enabled

by

transmitting

a

three-character

Control

Command

sequence,

either

from

the

terminal

keyboard

or

from

the

computer,

under

program

control.

The

selected

Operating

Mode

determines

when

data

is

sent,

how

much

data

is

sent,

and

when

it

is

necessary

to

press

the

pen

to

transmit

data.

Operating

Modes

and

mode

variables

are

descr.bed

in

the

Operating

Modes

and

Control

Com-

mands

descriptions

within

this

section.

When

enabled

and

operating,

the

Graphics

Tablet

transmits

digital

coordinate

data

corresponding

to

the

pen

.position;

this

data

is

sent

through

the

terminal

bus

to

the

terminal

display

and/or

to

the

computer.

The

use

of

this

data

is

defined

by

the

program

which

is

using

it.

It

may

be

used

to

define

single

points

which,

in

turn,

may

be

defined

as

some

value

or

answer

in

a

"menu

selection"

routine

Thedata

may

also

be

used

to

drawvectors

between

points'

or

rt

may

be

used

to

trace

or

input

a

curved,

continuous

Mne,

such

as

in

a

mapping

routine.

The

possiblities

are

dependent

on

the

computer

software

that

is

using

the

Q3T3.

Header

Characters

Each

coordinate

point

is

preceded

by

a

Header

Character

data

haf? TT^'

*

^

aPPr

°

Priate

™

de

to

a

«e

data

that

follows.

In

addition,

the

Header

Characters

are

used

.by

computer

software

to

interpret

the

data

string

that

follows

The

.parteular

Header

character

that

is

transmitted

before

each

coordmate

point

is

dependent

on

the

Operating

Mode

and

the

action

of

the

pen,

as

explained

in

each

Operating

Mode

description.

The

Graphics

Tablet

is

factory-wired

to

respond

with

one

of

four

Header

Characters.

(Header

Charac-

ters

may

be

changed

from

Control

Characters

to

letter

Son^

f

th

a

f

deSCr

,

ibed

'"

the

Stra

PP

able

Options

descrip-

tion,

but

the

terminal

will

display

M

and

characters

rather

than

graphics;

Local

Display

is

therefore

not

recommended

i

when

letter

Header

Characters

are

used)

om

menaed

I

Control

Commands

The

Graphics

Tablet

is

active

whenever

power

is

applied

to

both

the

terminal

and

the

Graphics

Tablet

The

tablet

,s

enabled

and

the

Operating

Mode

is

established

by

a

control

Command

sequence

consisting

of

three

ASCII

characters;

these

are

ESC

!

and

a

third

character

(Com-

iTn TTV**

firSt

five

bits

of

which

establish

the

vanables

of

the

Operating

Mode

(Table

2-2).

Command

SmtS.T k

6

!

e

'

eCted

f

°

r

the,r

desired

functi

°^

from

Table

2-3,

which

is

an

ASCII

code

chart

appended

to

hZI

li

fu

"

ctions

are

associated

with

each

character.

Note

that

the

Control

Command

sequence

does

not

print

on

the

terminal

screen

if

the

tablet

is

connected

and

.enacted.

2-2

REV

B.FEB

1979

Operation—

4953/4954

TABLE

2-1

Operating

Mode

Variables

Bit

Condition

1

(LSB)

2

(also

see

additional

functions)

«

Operation

Local

Display

On.

This

bit

condi-

tion

causes

the

transferred

data

to

be

displayed

on

the

terminal

screen.

Graphic

data

is

displayed

only

if

the

HEADER

strap

is

in

the

CONTROL

position.

If

the

HEADER

strap

is

in

the

LETTER

position

alphanumeric

characters

will

be

displayed;

Local

Display

is

not

recommended.

Local

Display

Off;

This

bit

condi-

tion

causes

the

data

to

be

transferred

through

the

terminal

bus

without

terminal

screen

dis-

play.

Multiple

Point

The

Tablet

is

allow-

ed

to

send

as

many

points

as

desired,

until

another

Control

Command

is

received

to

clear

the

tablet

or

change

operating

modes.

Single

Point

One

point

is

sent,

the

Tablet

then

is

disabled.

The

Tablet

must

be

enabled

again

with

another

Control

Command

to

send

more

data.

(Only

one

operation

is

allowed

for

leach

enabling.)

Operations

are

Data

Point

To

Host

Sending

Status

On

Leaving

Presence,

and

Disarming

the

Cross

Hairs.

Presence.

The

alpha

cursor

tracks

the

pen

when

the

pen

is

in

presence

(within

1/8

inch

of

tablet

surface),

.if

Local

Display

is

selected.

When

the

pen

is

pressed,

graphic

coordinate

points

are

sent

to

the

computer.

Information

for

positioning

the

terminal's

Alpha

cursor,

which

is

generated

while

the

pen

is

in

presence

and

the

pen

switch

is

open,

is

not

transmitted

to

the

computer

unless

the

COMSUP

strappable

option

is

in

the

OUT

position.

Pen.

A

coordinate

set is

sent

when

the

pen

is

depressed.

4

(also

see

additional

functions)

6

&7

Disable

on

Leaving

Presence.

Setting

this

bit,

with

the

status

strap

set

to

IN,

will

disble

the

Graphics

Tablet

when

the

pen

is

removed

from

tablet

presence

(lifted

1/8

inch

or

moved

past

the

presence

boundary)

if

the

terminal

is

ON

LINE.

The

Graphics

Tablet

must

be

enabled

again

to

send

more

data.

Regardless

of

the

condition

of

Bit

4,

an

INQUIRE

signal

is

transmitted

by

the

tablet

interface

when

the

pen'

leaves

presence.

INQUIRE

causes

the

terminal

to

place

its

current

status

information

on

the

data

lines,

just

as

if

the

terminal

had

received

an

ESC

ENQ

sequence

from

the

computer.

When

Single

Point

is

selected

(Bit

2)

and

the

pen

leaves

presence,

the

INQUIRE

signal

is

transmitted

the

next

time

the

tablet

is

enabled.

No

Disabling

on

Leaving

Presence.

Pen

Leaving

Presence

has

no

effect

on

the

Tablet

enable,

but

still

sends

terminal

status

if

the

status

.strap

is

set

to

IN.

12

bit.

12

bits

of

data

are

sent

for

each

coordinate.

(See

Graphic

Data

Input)

10

bit.

10

bits

of

data

are

sent

for

each

coordinate.

(See

Graphic

Data

Input.)

Not

used.

Additional

functions

Clear.

Any

character

with

bit

4

-

1

and

bit

2

=

will

clear

(disable)

the

tablet.

Terminal

status

will

automatically

be

sent

the

nexttime

the

Tablet

is

enabled

if

the

pen

leaves

presence

after

the

last

data

transmission.

Terminal/Tablet

interaction

Some

knowledge

of

the

terminal

operating

modes

is

required

for

complete

understanding

of

Graphics

Tablet

operation.

Refer

to

the

terminal

Users

Manual

for

such

information.

REV

B.FEB

1979

2-3

Operation—

4953/4954

TABLE

2-2

COMMAND

CHARACTER

ASCII

CHART

10

BITS

12

BITS

10

BITS

12

BITS

10

BITS

12

BITS

10

BITS

12

BITS

B7

86

B6

£

BITS

B4 B3

B2 E

*,

1

•',

1

».

,

^

1

1f

.

11

,

CONTROL

HIGHX8.Y

GRAPHIC

INPUT

LOWX

LOWY

i

a

N.UL

OLE

76

SP

32

48

@

64

p

80

\

96

P

772

LOCAL

OFF

SINGLE

POINT

P

E

N

P

R
£

I

N

C
E

1

SOH

7

DC1

17

I

33

1

49

A

65

Q.„

a

97

q

113

LOCAL

ON

1

(

3 STX

2

DC2

7a

7/

34

2

50

B

66

R

82

b

98

r

114

LOCAL

OFF

MULTI-

-

PLE

POINT

PEN

LEAVING

1

i

i ETX

3

DC3

79

#

35

3

57

C

67

S

83

c

99

s

775

LOCAL

ON

PRESENCE

HAS

1

c

5

EOT

4

DC4

20

$

36

4

52

D

68

T

84

d

700

t

776

LOCAL

OFF

LOCAL

ON

SINGLE

*

POINT

>N0

EFFECT

ON

1

1

ENQ

5

NAK

27

%

37

5

53

E

69

U

85

e

707

u

777

TABLET

ENABLE

1

1 (2

)

ACK

6

SYN

22

&

38

6

54

F

70

v

86

f

702

V

118

LOCAL

OFF

MULTI-

-

PLE

POINT

1 1 1

BEL

7

ETB

23

/

39

1

55

G

77

W

87

g

703

w

119

LOCAL

ON

10

BS

8

CAN

24

40

8

56

H

72

X

88

h

704

X

720

1

1

HT

9

EM

25

41

9

57

I

73

Y

89

i

705

y

727

>-

CLEAR

1

1

IF

70

SUB

26

42

-

«

58-

J

74

Z

90

J*

706

z

722

LOCAL

OFF

MULTI-

-

PLE

POINT

P

E

N

TABLET

1 1

1

VT

77

ESC

27

+

43

5

59

K

75

[

97

k

707

{

723

LOCAL

ON

IS

DISABLED

WHEN

PEN

LEAVES

1 1

FF

12

FS

28

5

44

<

60

L

76

\

92

I

708

I

1

724

CLEAR

P

1 1

1

CR

73

GS

29

45

61

M

77

]

93

m

709

}

125

PRESENCE

1 1

1

SO

74

RS

30

46

>

62

N

78

A

94

n

770

726

LOCAL

OFF

MULTI-

-

PLE

»

POINT

R

E

S

•

E

H

C

E

1

1

1 1

SI

75

US

31

/

47

?

63

79

~

95

111

fiUBOUT

(DEL)

727

LOCAL

ON

I79I-07

2-4

REV

A,

FEB

1979

Operation—

4953/4954

The

Graphics

Tablet

operates

in

four

basic

modes;

slight

differences

occur

depending

on

whether

Local

Display

is

selected,

whether

10

or 12

bits

of

data

is

to

be

transferred,

and

whether

it

is

desired

that

the

tablet

be

disabled

when

the

pen

leaves

tablet

presence.

The

four

basic

modes

are

Single

Point/Pen,

Single

Point/Presence,

Multiple

Point/Pen,

and

Multiple

Point/Presence.

All

modes

are

enabled

by

transmitting

a

Control

Command

sequence

consisting

of

three

ASCII

characters;

these

are

ESC

!

and

a

third

character

to

select

the

Operating

Mode

and

its

variables.

(See

Control

Commands.)

Regardless

of

the

Graphics

Tablet

Operating

Mode,

when

the

pen

is

brought

into

presence

and

the

terminal

is

in

Graphic

Plot

or

Alpha

Mode,

no

data

is

input

from

the

Graphics

Tablet,

if

COMSUP

is

strapped

IN as

described

in

Strappable

Options.

(Note

that

if

COMSUP

is

OUT,

Alpha

Cursor

positioning

data

is

transferred

to

the

computer.)

However,

if

the

terminal

is

ON

LINE

and

is

in

Graphic

Input

(GIN)

mode

with

the

crosshair

displayed,

the

Graphics

Tablet

sends

the

:

(colon)

Header

Character

when

the

pen

is

brought

into

presence.

This

causes

the

terminal

to

transmit

the

coordinates

of

the

crosshair

intersect

point,

and

causes

tbe

crosshair

cursor

to

dis-

appear.

Because

the

terminal

transmits

crosshair

position

data

bytes

in

the

reverse

order

of

the

Graphics

Tablet

(crosshair

transmission

order

is

HIX,

LOY,

HIY,

and

LOY;

Graphics

Tablet

transmission

order

is

HIY,

LOY,

HIX

and

LOX),

the

coitin

character

that is

followed

by

the

crosshair

coordinates

notifies

software

to

look

at

that

coordinate

data

string

in

reverse

order.

Software

can

then

be

readied

for

the

first

graphic

input

bytes

from

the

Graphics

Tablet.

(Note

that

if

Single

Point

is

selected

in

the

Operating

Mode,

transmission

of

the

crosshair

coordinate

disables

the

tablet;

it

must

be

re-enabled

with

another

Control

Command.)

Operating

Modes

NOTE

Do

not

change

Operating

Modes

while

the

pen

is

in

presence;

erroneous

Header

Characters

way

he

transmitted.

between

points,

vectors

are

drawn

between

successive

points;

the

alpha

cursor

is

not

displayed

after entry

of

the

first

point

The

first

point

after

entering

presence is

always

preceded

by

a

GS

Header

Character;

subsequent

points

are

preceded

by

a

SUB

Header

if

the

pen has

not

left

presence

between

points.

If

the

pen

leaves

presence

while

the

Graphics

Tablet

is

enabled,

it

signals,

the terminal

to

transmit

status

if

the

terminal

is

ON

LINE,

just

as if

it

had

received

an

ESC

ENQ

sequence

from

the

computer. If

the

pen

leaves

presence

after

data

has

been

sent, while

the

tablet

is

not

enabled,

then

status

will

be

sent

the

next

time

the

tablet

is

enabled.

If

the

Graphics

Tablet

is again

armed

for

Single

Point/Pen

and

the

pen

is

brought

into presence

and

pressed,

another

GS

Header

Character

is transmitted

followed

by

the

pen

coordinates;

the

alpha

cursor is no

longer

displayed.

Subsequent

points

are

again

preceded

by

SUB

Header

Characters.

Atypical

operating

sequence

is

illustrated

in

Fig.

2-4.

First-Time

Operation;

Single

Point/Pen

Mode.

This

procedure

may

be

used

to

familiarize

the

operator

with

the

characteristics

of

Single

Point/Pen

Mode

wben

operating

the

Graphics

Tablet

for

the

first

time.

1 .

Strappable

Options

should

be

in

their

factory-wired

positions:

COMSUP

in,

DELAY

in,

ESUP

out,

CR

out,

and

HEADER

in

the

CONTROL

position.

TheTablet

Size

strap

should

be

set to

SMALL

for

the

4953,

or

LARGE

for

the

4954.

2.

With

the

Graphics

Tablet

installed

and

with

power

applied to

the

tablet

and

the

terminal,

enable

the

Graphics

Tablet

for

Single

Point/Pen

mode

with

a

three-character

Control

Command

sequence

from

the

terminal

keyboard

(ESC

! 1

for

12

bits;

ESC

i A

for

10

bits).

The

READY

indicator

should

light.

3.

Place

the

terminal's

LOCAL/LINE

switch

in

the

LINE

position.

W

Single

Point/Pen.

Single

Point/Pen

mode

is

enabled

by

a

Control

Command

which

has

bits 2

and

3

=

in

the

Command

Character;

for

example,

ESC 11(12

bits)

or

ESC

! !

(10

bits).

In

this

mode,

a

single

coordinate

point,

preceded

by

a

GS

Header

Character,

is

sent

when

the

pen

is

depressed

in

the

presence

area

of

the

tablet;

the

tablet

is

then

disabled

from

sending

more

data

until

another

Control

Command

is

received.

After

another

Control

•

Command

is

received,

the

pen

may

be

pressed

again

to

enter

another

coordinate

preceded

by

a

SUB

Header;

pen

pressure

must

be

released

to

release

the

pen

switch

between

each

point,

but

the

pen

may

not

leave

presence.

If

Local

Display

is

selected

and

the

pen

remains

in

presence

4.

Bring

the

pen

into

presence

at

the

lower

left

corner

of

the

tablet,

(about

1-1/2 inches

in

from

the

bottom

and

left

tablet

margins),

and

press

the

pen

once.

The

DATA

and

PEN

indicators

should

blink,

and

the

READY

indicate

should

be

extinguished.

5.

Without

removing

the

pen

from

tablet

presence^

move

the

pen

to

a

point

half

way

up

the

tablet

surface

and

1-1/2

inches

in

from

the

right

margin.

Transmit

another

Control

Command

sequence

from

the

terminal

ke

y

boa

^

d

v

.Use

ESC

1

1

for

12

bits,

or

ESC

! A

for

10

bits.

The

READ

y

indicator

should

light.

REV.

A,

JULY,

1975

2-5

!

1

1

. „

If

if.

Operation—

4953/4954

i

! ,1

TEKTROISJIX

;

-

g

,

N,

Presence

Boundary

Resultant

Display

-

JL

(5

i

x

-t-

X

&

Pen Path

0-

Control

Command issued

(from

terminal keyboard or

from

computer); for example.

Esc

! 1.

Point

where

pen

is

pressed.

179.1-08

Fig.

2-4.

Operation

sequence in Single Point/Pen

mode. Note

that vectors are drawn between points

where

the

pen is pressed if

the pen

does

not

leave

presence.

If

the

pen

leaves

presence, two

Control Commands are

required

to

re-enable;

the

first

causes

Status

transmission and

the second enables

the tablet.

6. Press thepen. The

DATA

and PEN indicators

should

blink once, and the

READY indicator

should

be

ex-

tinguished.

On

the

terminal

screen,

a

vector

should be

displayed between the

lowlr

left

and

upper right corners

of the

screen.

7. Lift the pen from

presence,

and

while

it is lifted

send

the Control Command

(same as previously used)

from

the

terminal keyboard. Note

that when the

Command

Character (third character)

is sent, the

DATA

indicator

blinks once.

This occurs

when the

ENQ signal occurs,

causing

the terminal to

transmit

status. Repeat the

sequence

and

note

that the

READY

indicator illuminates.

8. Bring

the

pen into

presence

about

1-1/2

inches in

from the

lower right corner,

and press

the pen once.

The

DATA and

PEN indicators

should

blink

once,

and the

READY

indicator should

be

extinguished;

no display

should occur

on the

screen. Leave

the pen

in

presence.

9. Enable the Single

Point/Pen

mode with another

Control Command

(ESC ! 1

for

12 bits; ESC ! A for 10 bits)

from the

terminal keyboard.

The

READY indicator

should

illuminate.

10. Without

leaving presence,

move the pen

to a point

about

"1-1/2 inches

trom the left-hand.

tablet

border, about

3/4 of

the

distance

to the top

edge

ot the tablet.

Press

the

2-6

pen once;

the DATA and

PEN

indicators

should blink

once,

and

the

READY indicator

should

be extinguished.

A

vector

should appear on

the

screen,

from

the lower right

corner of

the screen to

the

upper

left

corner.

Single

Point/Presence. Single

Point/Presence

mode is

enabled by a

Control

Command

which

has bit2

-

and bit

3

=

1

in the Command

Character; for

Example,

ESC! 5

(12

bits)

or ESC

1

%

(10

bits). In:

this

mode,

one single

coordinate

point is compiled

and sent

for each

time the

tablet

is

enabled; however,

when

that

point

-is

compiled

and sent

is dependent

on

the

COMSUP

Strappable

Option.

When COMSUP

is strapped IN

(factory-set

position),

single

presence sends

no data

to the

computer

until

the

pen

is pressed while in presence.

Note,

however,

that

when

the

tablet is enabled for Single

Point/Presence

with

Local Display on, the

terminal's

alpha

cursor

tracks the

pen

as

long as

it

is in

presence and

not

pressed. When

the

pen

is

pressed, a single

coordinate

point

is

sent, preceded

by

a GS

Header and the

tablet is

disabled.

A

second point

may be sent

in several ways,

depending

on user

re-

quirements.

If

the pen is

held

depressed

while

the

Graphics

Tablet is

re-enabled,

then another coordinate

is

sent,

preceded

by

a

SUB

Header

Character, and

a

vector

is

drawn

between

the

first and

second point.

The point

which

is

transmitted

is

@

Operation—

4953/4954

W

the

pen

position

at

the

time

the

Control

Command

is

received.

If,

on the

other

hand,

pen

pressure

is

released

between

points

while

the

tablet

is

ra-enabled

with

another

Control

Command,

tnen

the

next

point

is

transmitted.

In

this

case,

the

second

point

is

preceded

by

a US

Header,

indicating

the

release

of

the

pen. If

the

Tablet

is

again

rearmed,

the

terminal

Alpha

Curser

will

track

as

before.

Using

this

procedure,

therefore,

alternates

GS

and

US

Header

Characters;

no

vectors

are

drawn

even

if

Local

Display

is

selected.

Note,

however,

that

if

the

computer

program

is

set

to

re-enable

the

tablet

as

soon

as

the

point

is

transmitted,

then

more

than

one

point

may

be

transmitted

for

each

pen

depression,

as

above.

The

intermediate

points

will

be

preceded

by

SUB

Header

Characters.

A

typical

operating

sequence

is

Illustrated

in

Fig.

2-5.

If

the

COMSUP

option

is

strapped

OUT,

operation

differs

in

the

following

ways.

When

the

tablet

is

enabled,

the first

point

is

transmitted

as

soon

as the

pen

enters

presence,

preceded

by

the

SUB

Header.

The

transmitted

coordinate

is

that

of

the

pen's

position

when

it

entered

presence.

If

Local

Display

is

selected,

the

terminal's

alpha

cursor will

move

to

the

display

position

relative

to

that

of

the

pen. If

the

pen

remains

in

presence

while

the

tablet

is

enabled

again,

another

point wit!

be

transm

itted

as

soon

as

the

Control

Command

Sequence

is

completed.

This

point

will

be the

coordinates

of

the

pen's

position

when

the

Control

Command

sequence

is

completed,

and

will

also

be

preceded

by

a

SUB

Header

Character;

the

cursor

will

move

to the

new

pen

location.

No

vectors

are

drawn

in this

mode, if

COMSUP

is

strapped

OUT,

but

coordinate

points

are

sent to

the

computer.

Regardless

of

the

condition

of

COMSUP,

if

the

STATUS

strap

is IN,

leaving

presence

causes

the

terminal

to

send

status,

as if

it

had

received

an ESC

ENQ

sequence

from

the

computer;

the

way

in

which

it is

sent

differs

somewhat.

If

COMSUP

is

strapped

IN,

this

occurs

in

the

following

ways:

If

the

Graphics

Tablet

is

enabled

with

the

pen

in

presence

but

the

pen

has

not

been

pressed,

status

is

transmitted

as

soon

as

the

pen

leaves

presence.

If

the

pen

has

been

pressed,

transmitting

a point,

and

the

pen

then

leaves

presence,

status

is

sent

when

the

next

Control

Command

is

received.

If

COMSUP

is

OUT,

the

pen

must

be

removed

from

presence

and

the

tablet

then

enabled;

status will

then

be

sent.

First-Time

Operation;

Single

Point/Presence

Mode.

This

procedure

may

be

used

to

familiarize

the

operator

with

the

characteristics

of

this

mode

when

operating

the

Graphics

Tablet

for

the

first

time.

1.

Strappable

Options

should

be

in their

factory-wired

positions:

COMSUP

in,

DELAY

in,

ESUP

out,

CR

out,

and

4ft-

.<£$:£

'7..;

TEKTROrSUX

-__-—

--KE)

£©---_----

©

Presence

Boundary

Resultant

Display

\™y

=

Control

Command

issued.

x

=

Point

where

pen

is

pressed

(and

held

pressed).

1791-09

Fig,

2-5.

Operation

sequence

in

Single

Point/Presence

mode.

Note

that

vectors

are

drawn

between

Control

Commands

if

the

pen

Is

held

depressed.

REV

A,

FEB

1979

2-7

Operation—

4953/4954

HEADER

in

the

CONTROL

position.

The

Tablet

Size

strap

should

be

set

to SMALL

for the

4953, or LARGE

for the

4954.

2.

With

the

Graphics

Tablet

installed

and with

power

applied

to

the

tablet

and the

terminal,

enable

Single

Point/Presence

mode

with

a

three-ciiaracter

Control

Command

sequence

from the

terminal

keyboard

(ESC

15

for

12

bits;

ESC

IE

for

10 bits).

The

READY

indicator

should

light.

3.

PlacetheterminarsLOCAL/LINEswitchintheLINE

position.

4.

Bring

the

pen

into

presence

atthe

lower

left

corner

of

the

tablet

(about

1-1

/2

inches

in

from

the

bottom

and

left

tablet

margins).

Press

the

pen

and

hold

it

depressed.

The

DATA

indicator

should blink

once,

the

READY

indicator

should

be

extinguished,

and

the

PEN

indicator

should

remain

lit

5.

Holding

the

pen

depressed,

move

it to a

point

about

1-1/2

inches

from the

right

tablet

margin/and

about

3/4

of

the

distance

to

the

top

margin

of

the

tablet.

6.

While

still

pressing

the

pen,

send

the

Control

Command

sequence

from the

terminal

keyboard

(ESC

!

5

for

12

bits;

ESC

I

E

for

10 bits).

The

DATA

and

READY

indicators

should

blink

once,

and

a

vector

should

be

drawn

on

the

terminal

screen

between

the

first

and

second

relative

points.

7.

Lift

the

pen

from

presence,

and

send

the

same

Control

Command

used

previously

from

the

terminal

keyboard.

The

DATA

and READY

indicators

should

blink

once.

Send the

sequence

again

and

the

READY

indicator

should

illuminate.

8.

"Repeat

steps

4

though

Bbetween

two

other

random

points;

a

vector

should

again

be

drawn

between

the

two

points,

Multiple

Point/Pen.

Multiple

Point/Pen

mode

is

enabled

by

a Control

Command

which

has

bit

2

=

1 and

bit

3

=

in the

Command

Character;

for

example

ESC

!

3

(12

bits)

or

ESC

! C

(10

bits).

This

models

used

for

drawing

straight

vectors

from

one

point

to

another,

with

a

single

enablingof

the

Graphics

Tablet.

Once

the

Graphics

Tablet

is

enabled,

if

the

pen

is

pressed

while

in

presence

a

single

coordinate

is

sent,

preceded

by

the

GS

Header

Character.

If

pen

pressure

is

released

(but

the

pen

does

not

leave

presence),

then

the

pen

moved

to

another

location

and

pressed

again,

a

second

point

is

sent,

preceded

by

a

SUB

Header

Character.

A

vector

is

drawn

between

these

points

if

Local

Display

is

selected.

Note

that

after

the

Initial

point

each

subsequent

point

is

preceded

by

a

SUA

Header

Character

as

long

as the

pen

remains

-inv.

presence

between

points

if

the

STATUS

strap

is

IN,

and

the

pen

is

removed

from

presence

status

is

transmitted

from

the

terminal,

flfld

the

next

transmjt

;

ted

point

is

preceded

by

a

GS

Header

Character

Thus

if

a

sequence

of

points

is

sent,

the

pen

lifted

out

of

presence

then

placed

back in

presence

and

pressed

a^ln,

no

vector

will

be

drawn

between

the

last two

points;

vectors

will

be

drawn

between

subsequent

points,

however,

**

long

as

the

remains

in

presence

between

pointy

A

typical

operation

sequence

is

illustrated

in Fig.

2-6.

NOTE

if

the

terminal

screen

is

erased

white

the

pen

is

in

presence

(by

pressing

the

PAQE.Jwy)

the

Graphic

Plot

mode

is

disabled.

No

lurthm

v&ctors

wi

J

rb

drawn

until

the

pen is

removed

from

presence

and

brought

back

into

presence

again,

This

will

enable

another

GS

Header

Character,

and

motors

will

once

again

be

drawn.

First-Time

Operation;

Multiple

Pofof/Pen

Mode

This

procedure

maybe

used

to

familiarize

»*

operator

with

the

characteristics

of

Multiple

Po\nt/p

m

Mode

.

operating

the

Graphics

Tablet

for

tr)®f

m\

tj

'

me

1.

Strappable

Options

should

be

totheir

factory-wired

positions:

COMSUP

in,

DELAY

in,

E$l#>

0ut

CR

y

"™

HEADER

in

the

CONTROL

position.

TI^TaWet

Stostao

should

be

set

to

SMALL

for

the

4953,

or

LARGE

for

the

4954.

2.

Witti

the

Graphics

TaWet

install

and

wjth

r

applied

to the

tablet

and the

terminal,^^^

Graphics

Tablet

for

Single

Point/Pen

mode

with

*

three^character

Control

Command

sequence

from

\h<;t&

tm

.

r

.~,

i,

Q

.,u„,,„,

(ESC i

3

for

12

bits;

ESC

1

C for

.10

S^SS

indicator

should

light.

'

e

HhADY

3.

Place

the

terminal's

LOCAL/LINf^

tctlintheL(NE

position.

4.

Bring

the

pen

into

presence

anci

^^

£

on

Th

PEN

and

DATA

indicators

should

^^mce

the

READY

indicator

should

remain

lit.

5.

Without

lifting

the

pen

from

.pf^rm

move

it

to

another

position

and

press

it

once

age*.

r

m

j

ndicators

should

blink

again,

and

a

vector

shou*

appear

between

the

first

and

second

relative

pen

poin&on

tie

-terminal

screen.

2-8

PS/A,

FEB

1979

Operation—

4953/4954

fig

.«#£*r-.:;

TEKTROfSJIX

i—

^

"•"'""''•'

--^-^"

'

-r,-'---i--.-.

.

"V.

/

\

/

\

X

\

X

X

\

\

/

\

\

S

\

^

-"

\

—

^

N

/

\

\

/

\

^.

*

"^X

*

Presence

Boundary

Resultant

Display

cc

-

Control

Command

x

=

Point

where

pen

is pressed.

Fig.

2-6.

Operation

sequence in Multiple

Point/Pen

mode. Note

that vectors

are

drawn

between

pen

depression points

as long

as

the

pen rerhains

in

presence

between

points.

6.

Lift the

pen from presence.

The READY

indicator

should blink

off momentarily

as the terminal

transmits

status.

7. Bring

the

pen back

into

presence and

press it again.

No

vector should

be drawn.between

this

point

and the last;

the indicators

should

blink

once.

pen is brought

into

presence,

the alpha

cursor

moves

to

the terminal

screen

position

relative

to the

pen's

position

on the

tablet.

As

long

as

the

pen is kept

in presence

and not

pressed,

the

terminal's

alpha

cursor follows

the

pen. If

COMSUP

is

strapped

IN,

this

cursor

positioning

data

(pen

coordinates)

is

not

sent

to the

computer; if

COMSUP

is

strapped

OUT,

pen

coordinates

are

continuously

sent

to

the

computer,

preceded

by

SUB Header

Characters.

B. Move the

pen without leaving

presence

and press

it

again; a vector

should

be drawn between this point

and

the

last.

Multiple

Point/Presence.

Multiple

Point/Presence

mode

is

enabled

by

a Control

Command

which has bits 2

and

3

=

1

in

the

Command

Character;

for example,

ESC! 7

(12

bits) or

ESC !

G

(10

bits). Multiple

Point/Presence

mode permits

a

continuous

sequence

of points

to be input

to the

terminal

and/or

computer,

permitting

graphic

representation

of the

pen's path. This

mode

may be

used

for

inputting

complicated lines,

curves,

etc.

When

the

Graphics

Tablet

is enabled for

Multiple

;

Point/Presence

mode with Local

Display

selected,

and the

Once the

pen

is

pressed,

closing

the pen switch,

all

further

coordinates

are

sent

to the

computer, as

long

as

the pen

remains

pressed.

The

first

coordinate is preceded

by a

GS

Header

Character;

subsequent points

are

preced-

ed

by a

SUB

Header

Character

and

vectors

are

drawn

between

coordinates

when

Local Display

is

selected.

Thus,

as long

as

the

pen is held

depressed

in the

presence

area

of

the

tablet,

coordinates

are continuously compiled

and

sent

out

to

the

computer.

The time

between

coor-

dinates,

and

therefore

the

pen

locations

that the

Graphics

Tablet will

transmit

to

the

computer and/or terminal, is

dependent

upon

DELAY

time

and the terminal's data

transmission

rate

when

the terminal

is On Line. (For

further

information

about

DELAY

time,

refer

to

the

description

in

Strappable

Options.)

@

2-9

Operation—

4953/4954

When

pen pressure

Is

released

(but

the pen kept

in

presence),

the

Graphics

Tablet

sends

the coordinates

of

the last

point

preceded

by

a

US Header

Character,

if

Local

Display

is

selected, the

terminal's

alpha

cursor appears

at

the screen

position relative

to the last

point

of the pen,

and

ioilows

the

pen

as long as

it remains

m presence.

No

vectors

are drawn

even though

coordinates

continue

to be

compiled

for alpha

cursor

positioning.

This

cursor

positioning

data

is not transmitted

to

the computer. If

the

pen

is

pressed

again, another

GS is

transmitted

and the

above

process

is repeated.

2.

With

the

Graphics

Tablet

installed

and

with

power

applied

to the

tablet

andihe

terminal,

enable

the

Graphics

Tablet

for

Multiple

Point/Presence

Mode

with

a

three-

character

Control

Command

sequence

from

the

terminal

keyboard

(ESC

!

7

for

12

bits;

ESC !

G<for

10

bits).

The

READY

indicator

should light.

3.

Place

the

terminal's

LOCAL/LINE

switch

in

the

LINE

position.

When the

pen

leaves

presence,

the

tablet

causes

the

terminal

to send

its current status

information,

just as

if

the

tablet has

received an

ESC

ENQ

sequence from

the

computer. This

occurs only if

the

terminal

is On Line.

A

typical

operation

sequence

Is illustrated

in

Fig.

2-7.

4.

Bring

the

pen

into

the

presence

area

of

the

tablet.

Press

the

pen;

hold it

pressed

and

move

it

around

on

the

tablet

surface.

The

PEN

indicator

should

remain

lit

as

long

as

the

pen

remains

pressed,

the

DATA

and

READY

indicators

should

blink

repeatedly,

and

the

pen's

path

should

be

displayed

on

the terminal

screen.

First-Time

Operation;

Multiple

Point/Presence

Mode,

This

procedure

may

be

used

to

familiarize

the

operator

with

the

characteristics

of Multiple

Point/Presence

Mode

when

operating

the

Graphics

Tablet

for

the

first

time.

1

.

Strappable

Options

should

be in

their

factory-wired

positions:

COMSUP

in, DELAY

in,

ESUP

out,

CR

out,

and

HEADER

in

the

CONTROL

position.

The

Tablet

Size

strap

shouid

be

set

to SMALL

for

the

4953, or

LARGE

for

the

4954.

5.

Lift

the

pen

from

presence.

The

READY

indicator

should

blink

off

momentarily

as

the

terminal

transmits

status.

GRAPHIC

DATA

INPUT

Any X

and Y

address

between

and

1023

(1024

points)

can

be

entered

to the

computer

and/or the

Terminal

buffers.

Data

input

to the

4010-series

buffers

causes

writing

beam

deflection

to the

point.

However,

Y

ad-

fc

'"

•
'

-

"

'

'

'

'

•

' '

"

—-—

--

-

—

-

.

"

.

'•

,

'

—

•'.Vii;

''

""rSKTRQNPC

/

\

Presence

Boundary

Resultant

Display

/

'

^l

cc

=

Control

Command

x

=

Point

where pen

is

pressed

(and

held

pressed).

R

=

Point

where

pen pressure

is

released.

Fig.

2-7.

Operation

sequence

in

Multiple

Point/Presence

mode.

Note that

the

pen's path

is drawn

on

the screen

as long

as

the

*

•

pen

is

held

depressed.

2-10

REV A,

FEB

1979

Operation—

4953/4954

dresses

greater

than

780

will

fall

outside

the

viewing

area

of

the

display.

Principal

address

locations

are

as

follows:

XLOY:

Bottom

screen

area

Top

of

main

screen

area

Left

of

screen

flight

of

screen

Y

=

Y-780

X

=

X=

1023

It

takes

20

bits

of

binary

data

to

establish

a

single

coordinate

address...10

bits

for

the

Y

coordinate

number

and

10

bits

for

the

X

coordinate

number.

However,

the

terminal

doesn't

handle

10

bit

numbers;

therefore,

each

number

is

divided

into

two

5-bit

bytes, 5

bits

representing

the

5

most

significant

bits

and

5

bits

representing

the

5

least

significant

bits.

Thus

a

point

coordinate

is

transmitted

in

four

5-bit

bytes

for

10-bit

operation.

For

each

coordinate

byte,J)its

1-5

contain

coordinate

information

(BIT

6

-

1,

BIT

7

-

U).

In

12-bit

operation,

data

is

sent

in

five

5-bit

bytes,

thus

allowing

up

to

4096

points.

The

Tablet

Control

card

controls

the

functioning

of

the

tablet

circuitry,

determines

the

current

X

and

Y

coor-

dinates,

and

assembles

this

information

in

a

suitable

format

before

putting

it

on

the

Terminal

minibus.

Data

is

transferred

as

a

Header

Character

followed

by

four

to

six

data

characters

as

follows:

H1Y:

This

contains

the

five

most

signifi-

cant

bits

of

the

Y

coordinate.

As

in

the

following

characters,

the

data

is

contained

in

bits

5

through

1

of

the

character.

LOY:

HIX:

LOX:

CR:

If

the

"12

Bit"

(bit

5

in

the

Command

Character)

is

a

zero,

the

XLOY

byte

will

not

be

sent.

When

the

"1

2

Bit"

is

a

one,

bit

5

of

XLOY

is

the

margin

bit

and

always

equals

0;

bits

4

and

3

are

the

least

significant

bits

for

the

Y

coordinate,

and

bits

2

and

1

are

the

least

significant

bits

for

X.

Bits

1

and

3

are

then

the

least

significant

bits

in

a

data

format,

1

2

bits

per

coordinate

value.

For

a

small

Tablet,

these

bits

contain

meaningless

data.

The

five

least

significant

bits

of

the

Y

coordinate,

except

in

12-bit

for-

mat

where

LOY

contains

bits

3

through

7

and

XLOY

contains

Y

bits

1

and

2.

The

five

most

significant

bits

of

the

X

coordinate.

The

five

least

significant

bits

of

the

X

coordinate,

except

in

12-bit

for-

mat

where

LOX

contains

bits

3

through

7

and

XLOY

contains

X

hits

1

and

2.

Optional

CR

carriage

return

character

(see

Strappable

Op-

tions).

™.

2-11

REV

A,

FEB

1979

4953/4954

Section

3

SUPPLEMENTAL

INFORMATION

W

%

AC POWER

REQUIREMENTS

The Graphics

Tablet is

intended

to

be

operated

from

a single-phase

power

source

that

has

one

of

its

current-carrying

conductors

(neutral)

at

ground

(earth)

potential.

Operation

from

other

power

sources

where

both

current-carrying

conductors

are live with

respect

to

ground

(such

as

phase-to-

phase on

a

multi-phase

system,

or

across

the

legs

of

a

1

15/230

volt

single-phase

three-wire

system)

is

not

recommended,

since

only

the

line

conductor

has

over-current

(fuse)

protection

within

the

instrument.

The

Graphics

Tablet

is

designed

to

operate

from

either

a

115-

or

230-volt

nominal

line

voltage

source

that

has

a

frequency of

50 to

400 Hz. In

addition,

either

of

two

voltage ranges

for

115 V

ac

or

230 V

ac may

be

selected.

Voltage,

current

and

power

requirements

are

listed

in

Table

3-1.

TABLE

3-1

4953/4954

Operating

Voltages

Nominal

Voltage

Tol-

erance

Voltage

Range

Frequency

Line

Fuse

Value

104

Vac

±10%"

94 to

114

Vac

48-440

Hz

0.3

A

115

Vac

104

to 126

Vac

slow-blow

208 V ac

187 to

228

Vac

0.2 A

230

V ac

207

to

253

V

ac

slow-blow

A fuse change

and

a

transformer

jumper

arrangement

permit

the

Graphics

Tablet

to

be

modified

to

suit

the

voltage

supply.

The

back

panel

identifies

the

internal

voltage

setting

for

which

the

unit

is wired

when

shipped

from

the

factory.

If the

jumper

arrangement

is

changed

for

any

reason

(changing

the

internal

voltage

setting)

attach

a

tag with

the

new

voltage

setting

to the

back

panel,

covering

the

old

setting.

AC

Power

Cord

and

Grounding

Requirements

This

instrument

has

a three-wire

power

cord

with

a

three-wire

terminal

polarized

plug

for

connection

to the

power

source

and

safety

earth.

See Fig.

3-1

for

USA

standard

plugs.

The

Safety

Earth

terminal

of

the

plug

is

directly

connected

to

the

instrument

frame

for

electric-

shock

protection.

Insert

this

plug

only

in a

mating

outlet

with

a safety

earth

contact,

or

otherwise

connect

the

frame

of the

unit

to a

safety

earthsystem.

The

color

coding

of

the

cord

conductors

is

in

accordance

with

recognized

stan-

dards

as

shown

below.

In

other

jurisdictions,

replace

the

USA

standard

plug

with

a

plug

that

satisfies

local

authorities.

POWER

CORD

COLOR

CODING

NOTE

The

power

cord

on

Tektronix

instruments

may

conform

to

either

of

the

following

two

electrical

codes:

Conductor

USA

(NEC)

&

Canada

1EC

Line

Black

Brown

Neutral

White

Light

Blue*

Safety-Earth

Green

w/yellow

stripe

Green

w/yellow

stripe

*

Tinned

copper

conductor.

USA

Standard Plug

for

200-240

Vac Only

cK

x"^\

6^/

^^^

TEKTRONIX

Part

No.

161-0099-00

USA

Standard

Plug

For

100-120

Vac

Only

^^^^

Vt

(l^\

[

>^

TEKTRONIX Part

No.

^^

161-0033-00

1791-12A

Fig.

3-1.

USA

standard

power

cord

plugs.

REV.

A,

JULY,

1975

3-1

Supplemental

Information—

4953/4954

LINE

VOLTAGE

SELECTION

To

change

the line

voltage

selection,

the

unit

should

be

disconnected

from

the

power

source.

Access

must

first

be

gained

to the

transformer

jumper

arrangement

on

the

Power

Supply

circuit

board,

within

the

Rower

Module.

This

consists

of

removing

4. screws

on

the

bottom

of

the

unit

and

removing

the

bottom

cover.

The

two

screws

that

attach

the

top

cover

may

then

be

removed,

and

the

top

cover

removed.

The

location

of the

jumper

connections

is

shown

in Fig. 3-2.

Wiring

instructions

are

shown

in

Fig.

3-

3.

Note

that

in

Fig.

3-3

the

dotted

lines

indicate

connec-

tions

between

transformer

wires

and

the

jumper

holes

on

the

circuit

board.

WARNING

Dangerous

voltages

exist at

several

places

inside

the

unit

Disconnect

the

Power

Module

from

the

power

source

before

changing

transformer

connections.

Power

may

still

be

applied

to the

transformer

and

several

other

points

unless

the

power

cord

is

disconnected.

Front

of

Power

Moduli

^

Jumper

S^^*

Holes

Fig.

3-2.

Line

voltage

jumper

hole

locations.

FUSES

There

is

one fuse,

located

at

the

lower

corner

of

the

back

panel.

The

line

voltage

fuse

is

a

0.3

A

slow-blow

fuse

for

operation

in the

1

1

5

V

ac range;

it

must

be changed

to a

CL2

A

-slow-Wow

fuse

for

operation

in

the

230

V

ac-

range.

RANGE

CONNECTIONS

TRANSFORMER

CONNECTIONS

104

1-8,

4-5

8

5

115

208

1-2,

3-4

5-8

f)

® ® 8

V

.

J

-I

V

Jumper

f~-§

$—

$

0,es

240 2-3

®

®

®

©

12

3 4

Front

of

Power

Module

-«$

179M4

Fig.

3-3.

Line

voltage

selection

wiring.

(Shown

strapped

for

115

V

ac.)

Broken

(dashed)

lines

indicate

permanent

con-

nections

between

transformer

wires

and

jumper

holes.

STRAPP

ABLE

OPTIONS

There

are

several

strappabie

options

on

the

4953/4954

Tablet

Control

card,

which

allow

certain

tablet

features

to

be

configured

to user

requirements.

The

function

of

these

strappabie

features

is as

described

in

the

following

section;

the

location

of

these

simps

is

shown

in

Fig,

3-4.

IN

OUT

nrfi

—

DELAY

IN

OUl

STATU

S

F1g.

3-4.

Tablet

Control

Card

strap

locations.

3-2

REV

A,

FEB

1

979

Supplemental

Information—

4953/4954

CR

¥

HEADER

LARGE/SMALL

DELAY

i

In some

systems,

OR is

interpreted

as

the

end

of

the

data

transfer.

When

connected

to

the

IN

posi-

tion,

the

tablet

generates

and

transmits

the

CR

(Carriage

Return)

after

each

generated

coordinate

point.

This

strap

is

to

accommodate

some

computer

systems

which do

not

accept

CONTROL

characters.

Each

data

string

originated

and

transmitted

by

the

tablet

is

preced-

ed

by a

Header

character,

which

determines

how

the

computer is

to

use

the

data

that

follows.

This

strap

is

normally

connected

in the

CON-

TROL

position

to

allow

proper

local

display

(when

selected).

If

Local

Display

is

selected

(see

Con-

trol

Commands)

-with

the

strap

in

the

LETTER

position,

M

and O

characters

will

be

written on

the

terminal

screen;

Letter

Headers

are

therefore

not

recommended

with

Local

Display.

The

HEADER

strap

allows

changing

the

Header

characters

as

follows:

CONTROL

LETTER

SUB

GS

US

-*»

O

The

position of

this

strap

causes

the

necessary

changes to

operate

the

LARGE

size

(4954)

tablet or

the

SMALL

size

(4953)

tablet.

The 4953

is a

10-bit

system; in

order for

this

to

fill the

terminal

screen

in

Local

Echo,

the

strap

is

placed

in

the

SMALL

positlon.Ttiis

shifts the

TO

bits

of

data

to

the

most

significant

10

bits of

the

12

allowed for

each

coordinate.

(12

bits of

data

may

still

be sent,

but

the

2 least

signifi-

cant bits

of

both

bytes

are

meaningless.

This

strap

selects

whether

or

not

a

delay

will

occur

between

each

coordinate

sent,

by

selecting the

delay IN

or

OUT.

With delay

IN,

there

is

an

adjustable 15- to

60-ms

delay

after

each

coordinate

sent.

With delay

OUT,

the

delay is

about

6-ms.

ESUP

(Echo

Suppression)

COMSUP

(Computer

Suppression)

If

delay

is

selected

OUT

or

if

delay

time

is

adjusted

too

short,

crt

damage

can

occur

in

Multiple

Point

Presence

mode,

with

4010,

4012,

and

4013

ter-

minals.

In some

systems,

the

computer

echoes

the

data sent

by

the Tablet.

When

that

data is

not to

be dis-

played, the

ESUP

strap

is

placed in

the

IN

position; the

terminal

will

then respond to

data

from the

tablet only

if

Local'

Display is

in

effect.

It is

recommended

that the

Tablet be

cleared,

using

a Control

Command

sequence,

prior

to

ad-

dressing

other

peripherals

if

ESUP

is

strapped in.

Certain

echoed

control

characters

do

get

through

to

the

terminal.

These

are

SOH,

ETX,

DC1

r

DC3,

HT, EM,

VT,

and

ESC.

Tte

COMSUP

option

affects

data

transfer

in

Multiple

Presence

and

Single

Presence

modes.

With

the

COMSUP

option

IN,

data

is

only

transmitted to

the

computer

when the

pen is

down and

the

Tablet

is en-

abled

or when the

pen

is

leaving

.

presence

(with

the

STATUS

strap

IN),

as

described

in the

Operation

Section.

When the

COMSUP

option is

strapped

OUT, data

is

transferred to

the

computer

whenever

the

Tablet

is

enabled

and

the pen

is in

presence.

The

strap is

normally

set in

the

IN

position.

(See

Multiple

Presence

in

the

Operation

Section

for

details on

Header

Characters.)

NOTE

On

Tablet

Control

Cards

prior

to

the

J1-4052

ver-

sion, the

strap

option

con-

sists of a

jumper

from

pin

2

of

U285.

When

the

strap

is

in, the

jumper

connects

to U175

pin

13;

when

the

strap

is out,

the

jumper

connects

to U285

pin 1

(Fig.

3-5),

REV

A, FEB

1979

3-3

Supplemental

Information—

4953/4954

CDMSUF

791-16A

Fig.

3-5.

Early

version

strap locations.

STATUS

The

Graphics

Tablet

has

several

modes

where

it will

cause

the

ter-

minal

to

transmit

status,

normally

when

the

pen

leaves

presence.

This is

described

in the

preceding

Operating

Modes

'descriptions,

where

it

is

assumed

that

the strap

is

in the IN

position.

With

this

strap in

the IN

position,

the

Graphics

Tablet

is operated

in

this

manner,

sending

status

as

described.

The

alternate

OUT

position

dis-

ables the.

Send

Status

operation.

All

other

operations

remain

the

same

When the strap

is

in the OUT

position;

the

Send

Status

step

is

merely

bypassed.

What

this

means

is that

the

operations enabling

se-

quences

remain

the same, but

the

terminal

will

not

send

its status

bytes

to the

computer.

For

example,

suppose that

the

Graphics Tablet

is enabled for

Single

Point/Pen

mode with the

pen

in

presence,

and

the

Statu

.

-;

,

:

strap

in

the

IN

position.

When

thf

pen leaves

presence,

the

table;

*'...:.,, causes the

terminal

to

transmit

status

to

the

computer

(when

operating

On-Line).

It

is

then

necessary

to

re-enable

the

Graphics

Tablet

to

send

another

point.

With

the

Status

strap

in

thf

OUT

position

and

operating

a

above,

leaving

presence

does

nc

cause

the

terminal

to

transrm

status.

The

Graphics

Table

behaves

however

as

if it

had

sent

i-

coordinate;

it is

still

necessary

tc

rearm

the

tablet

to send

anothe

;

point.

BIASING

THE

TABLET

The

Graphics

Tablet

contains

grids

of

magnetically

biased

wires

under

the tablet

surface.

The

biasing

is

done

at

the

factory,

but it

can

be

disrupted

if

a magnet

or

magnetized

article

is

placed

on the

Tablet.

This

will

result

in

digitizing

errors

(Fig.

3-6).

To

correct this

problem,

the

Tablet

must

be

rebiased.

Rebiasing

should

be

done

as

follows:

1. Place

the

magnet

on the upper

left corner

of

the

Tablet

surface,

as

shown in Fig.

3-7.

Be

sure

the

arrows

on

the

magnet

label

are pointing

as

shown.

2. Place one hand

on the center

of

tfee

magnet

assembly.

Apply pressure

to

the center of

the

magnet

assembly,

and

slowly

draw

the magnet

across

the

Tablet

surface

diagon-

ally

from the

upper left

to the lower

right.

This

should

be

done

in one

continuous, sweeping

motion

taking

two

or

three

seconds.

Do this

two

times,

being

sure

to

lift

the

..

magnet

clear off the

Tablet surface

when

again

placing

it

in

•

the

upper

left-hand

corner of

the surface.

3.

Store

the

magnet

away from

the Tablet

area.

STYLUS REFILL

REPLACEMENT

The

pen

stylus has been designed

to allow

the

user

to

replace the

ball point refill. This

can be done when

the

ink

is

exhausted

or when

it

is desired

to replace the

color.

To

replace the refill:

1

.

Unscrew

the front section

of the

stylus.

2.

Grasp

the

internal front

section,

and

carefully

pull

it

straight

off.

t

CAUTION

If

the

internal

front

section

comes

off with

the

outer

cover,

remove the

inner

section

before

attempting

to

reassemble

the

stylus,

or

you may

damage

the

miniature

connector.

3.

Pull

out the

refill,

and

replace

it with

a new

one.

4.

Replace

the

front inner section,

and mate

the

connectors.

5. Replace

the outer cover.

3-4

REV

C,

MAR

1980

Supplemental

Information—

4953/4954

TEKTROMIX

Pen

Path

1

I

i

pi

:

Resultant

Display

T-?l

Error

IBStillll

1 1

......

s

*

mm

mms^mmmmm

X

.1791-17

Fig.

3-6.

Error caused by

uneven

tablet

bias.

%?

^

%

A/

//7

x

\

\

\

\

IS

fTEK

ft

^

<

\

//

m..

\

BIASING

MAGNETJ/

mm

^M

\

\

S*/*

"y

'

m,

:

'

'

\

\

/W-'.f

^^tPpli

^^^5\

V

\

/£(*

Jr

Magnet

Path

\

lisitrt

Jllllllfl

\

;

';^^^

\

\

\

"i

..;.•

-

\

.:

•

\

•>

\

1791-18

fig.

3-7.

Biasing

the tablet.

@

3-5

4953/4954

Section

4

SERVICING

INTRODUCTION

Servicing

the

Graphics

Tablet

is

necessary

only

when

it

ceases

to

operate

properly;

routine

maintenance

is

not

required.

The

procedures

required

for

changing

the line

voltage

selection,

biasing

the

tablet's

magnetic

surface,

and

selecting

strappable

options

are

located

in

Section

3.

This

section

contains

a

Performance

Check

to

determine

whether

the

Tablet

is

operating

properly,

in

addition,

information

on

the

interconnecting

signals

and

a

general

overview

of

the

Graphics

Tablet

system

is

located

here.

Whenever

it

is

necessary

to

change

a

strap

position

on

the

Tablet

Control

card,

the

terminal

power

should

be

switched

off

prior

to

strap

positioning

unless

the

strap

can

be

reached

without

removing

the

card.

The

strappable

options

are to

be set

as

follows

except

where

specified

otherwise.

Do

not

remove

or

replace

circuit

cards

with

power

applied

to

the

terminal.

EQUIPMENT

REQUIRED

The

following

equipment

is

required

for

the

Perfor-

mance

Checks

to

the

Graphics

Tablet.

1.

Test

Oscillscope.

Bandwidth:

dc to

at

least

30

megahertz.

Minimum

deflection

factor:

5

millivolts

per

division.

For

example,

a

TEKTRONIX

Model

465

Oscilloscope.

2.

Precision

DC

Voltmeter.

Accuracy:

within

±0.5%.

Forexample,

aTEKTRONiXTM

SOOseries

mainframe

with

the

DM

501

Digital

Multimeter,

3.

Ohm

meter.

PERFORMANCE

CHECKS

Performance

Check

Strap

Positions

OR—

IN

HEADER-CONTROL

LARGE/SMALL—

Set to

appropriate

tablet

size

TRANSMIT

DELAY—

IN

ESUP—

OUT

COMSUP—

OUT

WA

RNING

I

When

the

Power

Module is

operated

with

the

cover

removed,

dangerous

voltages

are

present.

Be

careful

to

contact

only

the

instructed

points.

Performance

Checks

are to

be

made

with

the

Graphics

Tablet

connected

to

the

4010-series

terminal.

For

the

majority

of

the

checks,

this

is

the

only

equipment

required;

a few

of

the

checks

require

an

oscilloscope

or a

voltmeter.

For

the

purpose

of

this

procedure,

placing

the

terminal

ON

LINE

refers

to

placing

the

LOCAL/LINE

switch to

the

LINE

position,

with an

interface

installed

in

the

bus. It

is

not

necessary

to

be

connected

to

a

computer

for

this

check.

Miscellaneous

Circuit

Verifications

1 .

Check

the

relay

voltage

for

-9

to

-12

V,

measuring

from

ground

to

R317,

on

the

side

of

R317

(100

Q)

dosest

to

the

relay.

2.

Check

the 5

V

supply

across

U291

pins

7

(ground

and

14

(+5)

for

+5 V

+.05

V.

If

not

correct,

adjust

R89

on

the

Control

board

(within

the

Power

Module)

for

the

voltage

specified.

||

)

Prior

to

these

performance

checks

the

tablet

surface

V'

should

be

biased,

by

following

the

instructions

in

Biasing

the

Tablet,

Section

3.

3.

Check

the

voltage

across

U41

5

pins 7

(ground)

and

14

(4-5

V)

on

the

Control

for an

increase

of

less

than

0.2

V

from

the 5

V

across

U291

(step

2).

4-1

Servicing—

4953/4954

1

I

I

r-<—

500nsec

I

I

I

±100nsec

1

<„,

„„

j^Z.4V

««>»

<.4V

.;

^

ic en

.*>.<.«/«

..

^^^

1791-19

)T

Fig,

4-1.

Delay pulse timing.

4.

Place an oscilloscope probe

on

U301

pin 1.

Check

for a

positive pulse

of 2 to 4 ms

{3.2

nominally).

5.

Move

the DELAY

strap

to

the

OUT

position. Arm

with

ESC !

f.

The

repetition rate

of the

negative pulses

should

be

one

about

every

6 ms.

5. Arm

the

Tablet

with

ESC

!

6,

then place the

terminal

ON

LINE and

place the pen in presence.

Connect an

oscilloscope probe to

U281

pin 8.

Positive trigger

the

oscilloscope

on

U165

pin 1. The positive pulse that

occurs

on U281

pin 8*must occur

175

to

300 ns

(200

ns nominal)

after the oscilloscope

triggers.

This pulse is affected

by

C394,

R392, CR391, and

U281C (see

Fig.

4-2).

6,

Place the terminal back in

LOCAL

mode.

7.

Check

the

PEN signal

at J231-3 for low

signals

of

>0.4

V and high signals

of

^2.4V. The PEN light

should

light

when the

pen

is

depressed.

Delay Verification

1.

Place

the

terminal

in.

Local.

With the pen out

of

presence,

arm

the

Tablet with

ESC

!

i

The

READY

Indicator

will"light,

and the DATA

indicator

will

blink

once.

2.

Come into

presence,

but

do not

press the

pen.

READY will

be

dim, as it will

be blinking

rapidly.

The

frequency of

the

blinking

will

be dependent upon

the

setting of the Delay

potentiometer.

The

DATA indicator

will light.

3.

Connect

an oscilloscope

probe

to

TP235 and

check

the range of

R92,

the Delay

potentiometer. The

range

should

be 15

to 60

ms,

and

may

occur in steps.

4.

Adjust

R92 for

a

delay

of

approximately

30 ms

between

negative

pulses-

and check

for the pulses

shown

in Fig.

4-1.

With delay

strapped

OUT,

cri

damage can occur

on

4010, 4012,

and

4013

terminals, if

the

pen

is held

in

the

same

spot

for

too

long,

with

Local

Display

selected.

(Local display

should

not

occur during

this

check

4

6.

Place the

DELAY

strap

back to

the

IN

position.

U165-1

1

Trigger

U281-8

1

1

1

U-

1

1

^-1

-175 -300

nsec

1791-20

Fig.

4-2.

Bit

1 Verification

1

.

Page the

terminal.

With

the

pen

out

of

presence, arm

the

tablet with

ESC !

0.

The

READY

indicator should

light

and the

DATA

indicator

should

blink once.

2.

Place

the terminal

ON

LJNE. Bring

the pen into

presence, then

leave

presence;

the

Tablet

should then be

disabled.

d

4-2

@

Servicing—

4953/4954

3.

Return

the

terminal

to

LOCM^^pBration^ntlteartin

.Tablet

with ESC

I 0.

4.

Bring

the

pen

into

presence;

nothing

should

happen.

Press

the

pen and

the

Tablet

should

be

disabled.

Leave

the

pen

in

presence

with

no

pressure

applied.

5.

Rearm the

Table

with

€SC

1

N

.

The

READY

indicator

should be

illuminated.

6.

Bring

the

pen

into

presence,

but do not

press

the

pen.

The

READY

and

DATA indicators

should

blink

rapidly.

Place the

terminal

ON

LINE.

x
c
r

C

X

c

5.

Rearm

the

Tablet

with

ESC

!

0.

Press

the

pen

again

and

the

tablet

should

be

disabled.

Leave

the

pen in

presence

with

no

pressure

applied.

7.

Remove

the

pen

from

presence

and

the

Tablet

should

be

disabled.

The

READY indicator

should

be

extinguished.

6.

Rearm

the

tablet

with

ESC !

0,

and

place

the

terminal

ON

LINE.

Leave

presence

and

the

Tablet

should be

disabled.

The

cursor

should

stiJJ be in

the

home

position.

Bit

4

Verification

1. Place

the

terminal

in .LOCAL,

then

arm

the

Tablet

with ESC

! J.

7.

Return

the

terminal

to LOCAL,

and

arm

the

Tablet

with

ESC

!

A.

Come

into

presence

and

press

the

pen.

Type

Control

Shift

0;

the

alpha

cursor

should

reappear

on

the

terminal

screen

relative

to the

positron

where

the

pen was

pressed.

2. Bring

the

pen

into

presence

and

press

the

pen

several

times.

Note

that as

long

as

the

pen

remains

in

presence,

the

READY

and

DATA

indicators

blink

once

whenever

the

pen

is

pressed down.

Place

the

terminal

ON

LINE.

Bit

2

Verification

%

1.

Arm

the

Tablet

with ESC

IK.

3.

Leave

presence

and

the Tablet

should

be

disabled.

Place

the

terminal

in LOCAL.

2.

Place

the

terminal

ON

LINE, then

bring

the

pen

into

presence

and

press

the

pen

several

times

without

leaving

presence.

The

READY

and

DATA

indicators

should

blink

each

time

the

pen

is

pressed.

The

PEN

indicator

should

light

each

time

the

pen is

pressed,

and

remain

lit

until

pen

pressure

is

released.

4.

Rearm

the

Tablet

with ESC !

B.

5.

Bring

the

pen

into

presence

and

press

the

pen.

The

READYand

DATA

indicators

should

blink

once.

Place

the

terminal

ON

LINE.

3.

Leave

presence

and

the

Tablet

"strould

fce

disabled.

Bit 3

Verification

1.

Return

the

terminal

to

LOCAL

mode,

then

arm

the

Tablet

with

ESC

! J.

The

READY

indicator

should

light

6.

Release

pen

pressure,

then

remove

the

pen

Irom

presence.

The

READY

indicator

should

remain

il-

luminated.

7.

Bring

the pen

into

presence

and

press

the

pen.

The

READY

and

DATA

indicators

should

blink

once

for

each

pen

pressing.

Place

the

terminal

in

LOCAL.

2.

Bring

the

pen

into

presence

and

press

the pen

switch.

The

READY

and

DATA

indicators

should

blink

once;

the

PEN

indicator

should

remain

illuminated

as

long

as

the

pen is

pressed.

3.

Release

pen

pressure

but do

not

leave

presence.

The

READY

indicator

should

remain

illuminated;

the

others

should

be

extinguished.

Place

the

terminal

ON

INE.

4.

Remove

the

pen

from

tablet

presence

and

the

Tablet

should

be

disabled

i^m

READY

indicator

should

be

extinguished).

Place

the

terminal in

LOCAL.

8.

Clear

the

Tablet

with

ESC

! H.

The

indicators

should

be

extinguished.

Bit 5

Verification

1.

Connect

an

oscilloscope

probe to

pin

8

of

U421

or

pin 3

of

the

bus

and

set

the

oscilloscope

to

5

V/Div,

Negative

Trigger,

and 5

/is/Div.

...

2. Arm

the

Tablet

with

ESC

!

7

(12

bit).

Bring

the

pen

into

presence.

Seven

CSTROBE's

should

appear

on

the

oscilloscope

screen.

(Fig.

4-3).

4-3

Servicing—

4953/4954

3.

Leave

presence,

then

arm

the

ta

blet

with

ESC

!

G

(10

bit).

Bring

the

pen

into

presence.

Six

CSTROBE's

should

appear

on-t

he

oscillosc

ope

screen

(Fig.4-3).

There

will

be

a

missing

CSTROBE

between

the

second

and

third

CSTROBE.

Fig.

4-3.

Bit

5

verification.

4.

Leave

presence.

CR

Strap

Verification

1.

With

the

CR

strap

JN,

and

with

the

oscilloscope

connected

as

in

the

previous

check,

arm

the

tablet

with

ESC

i

6.

2.

Bring

the

pen

into

presence,

and

leave

it.

Seven

CSTROBE's

should

appear

on

the

oscilloscope

screen

(Fig.

4-4).

3.

Position

the

CR

strap

to

the

OUT

positron.

4.

If

it

has

l

eft

presence

,

place

thepen

in

presence

and

leave

it.

Six

CSTFTOBE's

should

appear

on

the

os-

cilloscope

screen;

OR is

not

strobed

on

to

the

bus

(Fig

4-

5.

Switch

the

terminal

power

off;

place

the

CR

strap

back

to

the

IN

position,

then

switch

terminal

power

back

on.

Disconnect

the

oscilloscope.

ESUP

Strap

Verification

1.

Switch

the

terminal

power

off,

position

the

ESUP

strap

IN,

then

turn

the

terminal

power

back

on.

Position

the

terminal

LOCAL/LINE

switch

to

LOCAL

and

arm

the

tablet

with

ESC

!

7.

2.

Bring

the

pen

into

presence,

and

the

alpha

cursor

should

move

to

the

relative

pen

position.

Press

the

pen

and

the

pen's

path

should

be

drawn

on

the

terminal

screen.

3.

Position

the

ESUP

strap

OUT.

Position

the

alpha

cursor

toward

the

center

of

the

screen

area,

then

position

the

ESUP

strap

in.

4.

Type

keyboard

characters.

HT

(TAB)

and

VT

are

the

e

j\i

Fig.474.

CR

strap

verification.

only

characters

that

should

get

through

ESUP

to

me

l

P)

i

terminal

display.

5.

Type

ESC

!

8

to

disable

the

tablet.

6.

Position

the

ESUP

strap

to

OUT.

All

characters

will

type

on

the

screen.

HEADER

Strap

Verification

1

.

Arm

the

Tablet

with

ESC I

7.

2.

Bring

the

pen

into

tablet

presence

and

press

it.

The

pen's

path

should

be

displayed

on

the

terminal

screen

as

long

as

the

pen

is

pressed.

3.

Release

pen

pressure

and

the

alpha

cursor

should

appear

on

the

screen

at

the

pen's

relative

position

on

the

screen.

The

cursor

should

follow

the

pen

as

long

as

it

remains

in

presence.

4.

Press

the

pen

again

and

go

off

the

edge

of

the

tablet.

The

alpha

cursor

should

appear

at

a

point

on

the

valid

jT)

))

screen

viewing

area

-

.

a;

'//'

4-4

@

Servicing—

4953/4954

c

5.

Move

the

HEADER

strap-to

LETTER.

Bring

the

pen

into

presence

and

press

it.

An

M should

appear

when

the

pen

is

pressed,

and

an

O

when

pen

pressure

is

released.

The

cursor

should

follow

the

pen

when

it

is

in

the

tablet's

presence.

6.

Place

the

HEADER

strap

back

to

CONTROL.

Crosshair

Operation

Verification

1.

Place

the

terminal

in

LOCAL,

move

the

pen

out

of

presence,

and

arm

the

Tablet

with

ESC

!

C.

4.

Release

the

pen;

the

alpha

cursor

shoutd

appear

again,

and

track

the

pen

on

the

terminal

display.

5.

Place

the

COMSUP

strap

back

into

the

desired

position.

Major

Component

Verification

If

the

Graphics

Tablet

fails

to

operate

properly

even

after

other

performance

checks

have

been

performed

and

the

tablet

has

been

biased,

the

following

procedure

may

be

used

to

check

performance

of

the

tablet

proper,

the

pulser,

and

the

preamp.

2.

Type

ESC

SUB

(CNTRL

Z)

from

the

terminal

fceyboard.The

terminal

crosshaircursoT

should

appearon

the

screen.

1.

Remove

the

tablet

cover

by

first

removing

the

attaching

screws

from

the

tablet

frame.

3.

Place

the

terminal

ONLINE,

then

bring

the

pen

into

presence

but

do

not

press

it.

The

crosshair

should

disappear.

4.

Place

the

terminal

into

LOCAL.

Press

the

RESET

key

on the

terminal.

Arm

the

Tablet

with

ESC !

G.

Type

ESC

Ctrl

Z

to

turn

on the

terminal

crosshairs.

5. Place

the

terminal

ON

LINE.

6.

Lift

the

pen

out

of

presence.

Nothing

should

happen.

7.

Bring

the

pen

back

into

presence.

The

crosshair

cursor

should

disappear.

COMSUP

Strap

Verification

1.

Place

the

COMSUP

strap

fn

the

IN

pos

ition,

and

place

an

oscilloscope

probe

on the

CSTROBE

line

(pin

3

of

the

bus

or

pin

8

of

U421C

on

the

Tablet

Control

card).

Set

the

oscilloscope

to

2 V/Div,

Negative

Trigger,

and

5 /is/Div.

2.

Arm

the

Graphics

Tablet

with

ESC !

7.

Bring

the

pen

into

presence;

the

alpha

cursor

sho

uld

track

the

pen

on

the

terminal

screen,

but no

CSTROBE's

should

appear

on

the

oscilloscope

display.

3.

Press

the

pen;

the

pen's

path

should

be

displayed

on

the terminal

screen

and

CSTROBE's

should

appear

on the

oscilloscope

display.

2.

Connect

an

oscilloscope

probe

to

the

X-axis

pulser

wire

at the

upper

left

corner

of

the

tablet

(Fig.

4-5), and

connect

another

probe

to

trigger

from

the

rising

edge

of

the

FIREX

pulse

(J231-7

on

the

Tablet

Control

card).

Set

the

oscilloscope

to

10 V/Div,

1 #s

per

division.

The

displayed

waveform

should

resemble

that.

in

Fig.

4-6.

pip

•

*

mm'*

-axis

pulser

wire

j

I

.

•

-'

•

•;•

•

'

<

*

><>

~

, I

.

-

I

—

•

'

'

?

|

j

rf

*

*

t><

t

,

z.

r

mm

1

'

*

i

'

'

i

1791-23

Fig.

4-5.

Pulser

wire

locations.

3.

Repeat

step

2

for

the

Y-axis

pulser wire

(Fig.

4-5),

triggering

from

the

FI'REY

pulse

(J231-6).

The

displayed

waveform

should

resemble

that

in Fig.

4-7.

4.

If

one or

both

of

the

above

waveforms

are

not

as

specified,

disconnect

the

tablet

and

measure

with

an

@

4-5

Servicing—

4953/4954

j

178.1-24

j

Fig.

4-6.

X-axis

wire

pulsing

waveform.

Fig. 4-7.

Y-axis

wire

pulsing

waveform.

Fig. 4-8.

FIREX/FIREY

waveform.

trigger

from

the

FIREX

pulse,

and

to

display

1 V/Div

and

5

/is/Div.

The

displayed

waveform

should

resemble

that

in

Fig. 4-10.

(The

pen

must

be

in

presence.)

8.

Repeat

step

7

above,

triggering

from

the

FIREY

pulse.

The

same

waveform

should

occur.

9.

If

the

above

checks

(steps

7

and

8)

are

not

as

specified,

disconnect

the

pen

and

measure

between

pins

1

and

7

of

the

pen

cable

connector

(P1012)

for

a

measure-

ment

of

about

D.

Substantially

higher

resistance

in-

dicates

a

bad

pen

or

pen

cable.

If

not,

the

pen

preamp

may

be

bad;

proceed

to step

10.

ohmmeter

between

pins

1

and

2

of

the

tablet

connector

(P1

01

4)

on

the

end

of

the

tablet

connector

cable.

Repeat

for

pins

3

and

4;

both

should

measure

about

1 O.

5.

If

the

tablet

checks

out

properly,

replace

the

frame

and

the

four

attaching

screws,

then

check

the

FIREX

and

FIREY

pulses

(J231-7

and

J231-6,

respectively).

This

is

accomplished

by

placing

an

oscilloscope

probe

on

the

appropriate

connector

and

setting

the

oscilloscope

to

positive

trigger

internally.

Set

the

oscilloscope

controls

for

2

V/Div

and

2

//s/Div.

The

pulse

for

each

axis

should

resemble

that

in

Fig. 4-8.

If

not,

thepulser

is

not

operating

properly.

6.

Remove

both

covers

from

the

Power

Module

by

first

removing

the

four

screws

that

attach

the

bottom

cover,

then

the

two

internal

screws

that

attach

the

top

cover!

Remove

the

cover

from

the

pen

preamp

by

removing

the

two

attaching

screws.

7.

Attach

an

oscilloscope

probe

to

pin

12

of

the

72702

1C within

trie

preamp

(Bg.

.4-9).

Set

the

oscillmc0pe

to

10.

Place

an

-oscilloscope

probe

on

pin

12

of

U415

on

the

Power

Supply

board.

Set

the

oscilloscope

to

5

V/Div,

5

/is/Div,

and

connect

again

to

triggerfrom

the

rising

edge

of

the

FIR£X

pulse.

The

displayed

waveform

should

approximate

that

in Fig. 4-11,

11.

Repeat,

triggering

from

FIREY;

a

similar

waveform

should

occur.

(Note

that

the

horizontal

position

of

the

pulses

moves

according

to

the

pen

position,

in

both

steps

10

and

11.)

12.

If

these

pulses

do

not

occur,

the

preamp

is

not

operating

properly.

13.

After

all

checks

and

any

necessary

replacements

are

completed,

replace

the

top

cover

on

the

Power

Module

and

secure

it

with

the

two

attaching

screws.

Then

replace

the

bottom

cover

and

secure

it

with

its

four

attaching

screws.

Connect

the

components

together

as

described

in

the

Installation

description.

M

4-6

Servicing—

4953/4954

Fig.

4-9,

Preamp

test

point

location.

mmmim

warn

1791-28

—HIPS

Fig.

4-10.

Preamp waveform.

This

waveform

is

very

sensitive.

The probe must

connect

directly

to pin

12

(not through

a

clip-

extender),

or the

nearest

lead of the

150

pF

capacitor.

Note

also

that

variation

may occur between

tablets, due

to

biasing

and

pen

position.

Fig. 4-11.

DONE

pulse

waveform.

"W

@

4-7

Servicing—

4953/4954

INTERCONNECTING

SIGNALS

The

Graphics

Tablet

operates

as

a

peripheral

to

the

4010-series

terminal,

with

theTablet

Control

card

plugged

directly

to

the

terminal

bus.

The

interconnecting

signals

between

the

terminal

and

theTablet

Control

card

conform

to

the

bus

signal

definitions

and

descriptions

found

in

the

terminal

manual.

The

interconnecting

signals

between

the

Tablet

Con-

trol

card

and

Power

Module

are

defined

in

Table

4-1;

locations

are

shown

in

Table

4-2.

TABLE

4-1

Power

Module

to

Tablet

Control

Card

Signal

Definitions

Signal

Name

FIREX

FIREY

OFFSET

DONE

PEN

Function

FIREX

goes

high

to

initiate

the

transmission

of

the

wave

along

the

X-axis

wires

in

the

tablet.

Each

FIREX

pulse

is

at

least 5

/is long;

wave

transmission

occurs

ap-

proximately

3/iS

after

the

FIREX

pulse

occurs.

When

the

X-axis

pulse

is

sent,

it

momentarily

pulls

the

FIREX

signal

down.

It

is from

the

falling

edge

of

this

timing

reference

mark,

within

the

FIREX

pulse,

that

all

timing

occurs.

Identical

to

FIREX,

but

for

the

Y-

axis.

This

signal

is

the

result

of a

strap

within

the

PEN

connector,

to

determine

whether

the

pen or

the

cursor

is

being

used.

When

the

pen

is

connected,

OFFSET

is

ground-

ed.

DONE

goes

low,

upoadetection

of

the

tablet

wave,

to

sto

p

the

X

and

Y

position

counters.

DONE

also

goes

low

when

either

of

the

tablet

waves

are

sent;

these

pulses

are

disallowed

by

circuitry

on

the

Tablet

Control

card.

PEN

goes

low

when

the

pen

(or

cursor

button)

is

pressed.

The

PEN

indicator

on

the

Power

Module

lights

whenever

PEN

is

present.

READY

DATA

RVCC

READY

goes

low

when

the

tablet

is

armed

and

ready

to

transmit

data.

The

READY

-indicator

lights

when

READY

is

present.

DATA

goes low

when

data

is

being

transferred

from

the

tablet

inter-

face

to

the

screen

and/or

com-

puter.

The

DATA

indicator

il-

luminates

when

DATA

is

present.

RVCC

senses

the

4-5

V

on

the

Tablet

Control

card

for

power

regulation

on

the

Power

Supply

board.

+5

GROUND

-F15

-15

SHIELD

GROUND

4-5

V

at

1

.4

A

trom

the

Power

Module

to

the

Tablet

Control

card

(2

lines).

3

wires

4-15

V

at

40

mA

from,

the

Tablet

Control

card

to

the

Power

Module.

-15

V

at

80

mA

from

the

Tablet

Control

card

to

the

Power

Module.

A

relay

in

the

Power

Module

prevents

the

tabletfrom

turning

on

when

-15

V is

not

present.

Shield

ground

is

to

be

connected

to

chassis

ground

in

the

terminal

pedestal;

it

is

connected

to

chassis

ground

within

the

Power

Module

through

an

RC

filter

network.

TABLET

DIGITIZATION

When

the

tablet

is

installed

and

power

is

applied

to

the

tablet

and

the

terminal,

the

Tablet

Control

card

is

reading

Bits

1-7

on

the

terminal

bus

to

detect

an

enabling

Control

Command

sequence.

When

ESC

!

and

a

third

ASCII

character

are

detected,

the

tablet

is

enabled

and

ready

to

transmit

digitized

points.

The

bits

in

the

third

character

of

the

Control

Command

determine

the

operating

mode,

which

in

turn

determines

how

many

points

will

be

sent,

under

which

conditions

they

will

be

sent,

and

how

many

bits

define

each

point.

Tablet

Digitization

is

accomplished

by

sending

a

180-

|

volt

pulse

simultaneously

along

ail

wires

of

one

axis

(X-

J

I

axis)

under

the

tablet

surface,

followed

by

1he

other

axis"

(Y-axis).

When

a

pulse

is

fired,

it

causes

an

acoustical

4-8

Servicing—

4953/4954

TABLE

4-2

Power

Module

to

Tablet

Control

Card

Signal

Locations

During

the

next

96 counts

of

the

.21.08

MHz

clock,

a

POWER

MODULE

CONNECTION

BACK

PANEL

CONNECTION

TABLET

CONTROL

CARD

CONNECTION

SIGNAL

J237-1

J1010-7

J231-7

FIREX

J237-2

J

101

0-6

J231-6

FIREY

J237-3

J1010-5

J231-5

OFFSET

J237-4

J101Q-4

J231-4

DONE

J237-5

J1010-3

J231-3

PEN

J237-6

J

101

0-2

J231-2

READY

J237-7

J

J1010-1

J231-1

DATA

J236-1

J1010-24

J232-8

-15

J236-2

J

101

0-23

J232-7

+15

J236-3

J1010-13

J232-6

GROUND

J236-4

J1010-12

J232-5

GROUND

J236-5

J1

01

0-11

J232-4

GROUND

J236-6

J1

01

0-10

J232-3

+5

J236-7

J1010-9

J232-2

+5

J236-8

J1010-8

J232-1

RVCC

J1010-18

Spade

Shield

%

Connector

Ground

w

wave

to

travel

along

the

wires;

a coil

in

the

pen

or

cursor

can

then

detect

the

wave/The

time

between

the

firing

of

the

pulse

and

detection

of the

wave

by

the

coil

in

the

pen

determines

the

pen's

position

on

the

tablet

surface.

When

the

pen

detects

this

wave,

a

DONE

pulse

is

generated,

stopping

the

appropriate

axis

counters.

The

counters

for

both

axes

operate

at

21

.08

MHz,

causing

each

tablet

clock

pulse

to

represent

0.01 incti

of

wave

travel

This

process

is

occurring

whenever

the

tablet

is

installed

and

the

power

applied;

it

is

used

by

the

counters

only

-when

the

tablet

is

enabled,

however.

The

180-volt

pulse

is

fired

by

the

tablet

pulser

upon

receipt

of

a

FIREX

(or

FIREY)

signal

from

the

tablet

sequencer

on

the

Tablet

Control

card.

When

the

pulse

is

actually

sent,

FIREX

or

FIREY

is

momentarily

pulled

low.

This

momentary

low

is

the

timing

reference

mark

for

the

appropriate

axis'

counter;

all

timing

is

done

from

the

falling

edge

of

the

timing

reference

mark.

The

DONE

pulse

is

a

result

of

the

detection

by

the

pen

(or

cursor)

of

the

acoustical

wave

in

the

tablet.

It is

shaped

by

the

Preamp

and

s

ent

to t

he

Tablet

Control

card

to

stop

the

counters.

Due

to

DONE

puls

es that

may

occur

during

the

firing

of

the

180 V

pulse,

DONE

pulses

occurring

during

the

first

128

counts

of

the

21.08

MHz

clock

are

ignored.

This

delay

changes

to

120

counts

if

the

tablet

cursor

is

being

used,

due

to the

larger

diameter

of

the

cursor

pickup

coil.

DONE

pulse

indicates

that

the

pen

is to

the

left

or

the

top

of

the

working

area

of

the

tablet

This

is

considered

to

be

an

Out-of-Presence

condition.

After

these

delays,

the

counters

begin

to

count

until

a DONE

pulse

stops

them;

it

is

this

digitized

count

that

determines

the

pen

coordinates.

If

the

counter

counts

past

its

maximum

value,

an

Out-of-

Presence

condition

exists

again.

For

more

information

on the

Digitization

procedure,

refer

to

the

timing

diagram

in

Fig. 4-12.

In

addition,

a

Block

Diagram

and

description

follow

in

this

section.

BLOCK

DIAGRAM

DESCRIPTION

The

Graphics

Tablet

Block

Diagram

(Fig.

4-13)

is

a

simplified

view

of the

Graphics

Tablet,

and

is

provided

to

give

an

overall

view

of

the

operation

of

the

Graphics

Tablet

circuitry.

Each

of

the

blocks

represents

some

section

of

the

circuitry

on

the

Tablet

Control

card,

or

else

one

of

the

major

replaceable

components

(the

tablet,

pulser,

or

preamp).

The

operation

1

of

each

circuit

block

is

further

detailed

in

the

Circuit

Description

section

of

this

manual.

The

circuit

blocks

function

together

as

described

in

the

following

paragraphs.

The

Tablet

Clock

provides

the

operating

frequency

for

the

tablet,

with

each

pulse

of

the

21

.08

MHz

clock

representing

0.01

inch

of

acoustic

wave

travel

on

the

tablet

surface.

This

clock

is

synchronized

with

the

divided

614

kHz

clock

in

the

Sync

circuitry,

and

inputto

the

Tablet

Sequencer.

The

Tablet

Sequencer

is

responsible

for

the

FIREX

and

FIREY

signals,

which

cause

the

Pulse.r

(within

the

Power

Module)

to

sequentially

fire

the

X

and

Y

180 V

pulses.

These

pulses

cause

an

acoustical

wave,

to travel

along

the X

and Y

axis

wires

in

the

tablet

and be

detected

by

the

pen.

At

the

same

time,

the

Wait

One-Shot and the

Digital

Delay

portion

of

the

circuitry

prevent

the Tablet

Sequencer

from

accepting

extraneous

DONE

signals from

the

Preamp,

which

occur

when

the

1.80

V

pulse is fired.

The

Tablet

Sequencer

also

provides

the

Tablet Clock

to

the X

and

Y

Coun

ters.

The

counters

continue

to

operate

until

a

valid

DONE

pulse

is

received

from

the

Preamp.

The

DONE

pulse

indicates

that

the

pen

has

sensed

the

acoustic

wave

traveling

past

the

pen

position.

Since

the

counters

register

the

number

of

counts

since the

wave

started,

and

since

each

count

represents

a set

wave

travel

distance,

the

position

of

the

pen

with

respect to

the

starting

position

of

the

wave

has

been

determined.

This

count

is

latched

into

the

Output

Shift Registers

to

be

transferred

onto

the

terminal

bus.

Another

portion

of

the

circuitry

provides

for

Tablet

enabling.

This

circuitry

begins

with

the Address

Decoder;*:.

4-9

Servicing—

4953/4954

Delays

finished

*

~n

>5/is

F1REX

m

•Timing

reference

mark

6ms

*

DOME

DONE

indicates

out of

presence

r

A.Sjjls

U-

Dependent

on

tablet

size

%

1

'-JP"-

Bala

)

valid

[

]__

No DONE

signal

before

this

point

indicates

an out

of

presence

condition.

DONE

M

"Digital

delays;

see tablet

digitization.

w

Stop

counters

Fig. 4-12.

Graphics

Tablet

timing.

which

senses

the

bits

.on.

the

terminal

bus

lines.

When

a

sequence

of

ESC I

is

detected,

tbe

tablet

is

armed;

the

next

character

is

then

latched

into

the

Command

Character

Buffer.

The

bits

in

this

third

character

determine

the

specifics

of

the

Graphics

Tablet

operating

mode.

The

Pen

Mode

circuit

block

allows

transmission

of

coordinates

only

when

the

pen

is

pressed,

and

when

the

Tablet

is

armed

for

pen

mode.

Otherwise,

the

Transmit

Initiate

block

is

allowed

to

operate

freely

when

the

Tablet

Sequencer

is

ready

to

initiate.

a sending

sequence.

The

Transmit

Enable

block

determines

when

the

initiation

can

begin

(through

the Delay

One-Shot)

and

how

many

points

can

be

sent,

dependent

on

whether

the

tablet

is

set

for

Single

or

Multiple

Point.

When

the

above

conditions

are

all

met,

the

Output

Sequencer

is

allowed

to

initiate

a

sequence

of

outputting

the

graphic

bytes

to

the

terminal

bus.

It

enables

the

Output

Shift

Registers

to

begin

transmission,

and

allows

the

Character

Identifier

and

Strobes

Out

blocks

to

begin

placing

theappropriate

Identifier

signals

on

the

bus,

along

with

the

appropriate

Strobes.

The

Pen

Status

block

enables

the

appropriate

headers

and,

when

Comsup

is

4-10

@

Servicing—

4953/4954

'"*<.

v

1791-31

Fig. 4-13.

Graphics

Table!

Block

Diagram.

strapped

in,

allows

CSTROBES

only

when

the

pen

is

pressed.

The

ESUP

block,

when

strapped

in,

suppresses

the

terminal

to echoed

data

characters.

The

three

presence

blocks

(Presence

Latch,

True

Presence,

and

Presence

Status)

enable

the

appropriate

Header

Characters

for

the

pen's

presence

status,

and

initiates

transmission

when

the Tablet

is armed

for

Send

on

Presence. In

addition,

the

Presence

Status

enables

the

Enq

Generator

when

the pen

leaves

presence,

so

that

an

Enq

signal

is

then

placed

on

the

bus.

@

4-11

4953/4954

Section

5

CIRCUIT

DESCRIPTIONS

TABLET CONTROL

CARD

Tablet

Clock

The Tablet

clock (see Tablet Control

Card Diagram)

is

a

crystal-controlled

oscillator that

provides

the

21

.08

MHz

square-wave frequency necessary

for the Tablet

counters

to- operate*. Each .clock pulse represents

Q.01

inches

of

wave travel

on the wires within the tablet

Divide-by-four

U201

(A&B)

form

a

divide-by-four

circuit/This

divides

the 614

kHz

terminal

clock down to 153

kHz.

Dela

y

and

Wait One-shot.)

After

the

Digital Delay,

assum-

ing LJNDERFEoW

does

not occur, t

he

X-counter

is

enabled

by

U31A,

and c

ounts until a

DONE pulse

is

receive

d

or XOVERFLOW

occurs

on

pin.

3 of U163.

The

DONE

pulse

clears

U131A,

which disables U31A.

At the

end

of

the 3 ms pulse outputfrom

the Delay

one-

shot,

the 153

kHz dock

is re-enabled.

Trie

next pulse

from

U1

1

1 A then

produces a

high

on

pin 9 of

U21

1B.

U1

1

A

then

produces a FIREY

pulse on

J231 pin 6.

The

Wait

and Count

sequence

follows the

order that occurred for

the

X

count;

counting

begins with

the timing reference

mark in

the

FIREY

signal.

Sync

This

portion

ofthe

circuit,

consisting of

U1

11

A,

delays

the

153.

kHz

clock

generated

above

to coincide

with

the

21.08

MHz

clock. The

output of

U111A (pin

5)

provides

clocking for

the

Tablet Sequencer,

Tablet

Sequencer

This portion

of

the

Tablet

Control card

consists

of

3

flip-flops

(U211A,

U211B, and

U11-1B)

and

associated

gates to

determine the

output functions

of the flip-flops.

When

initialized,

pins

5

and

9

of the three

fJtp-fiops

are

all

low. This

is the

load condition

of the

sequencer,

and

preloads the

X

and

Y

counters withtheir

initial

values.

tThe

counters

are described in detail

elsewhere

in these

circuit

descriptions.)

At the

end

of the 3

ms

delay

for

the

Y count,

the

153

kHz

clock

is re-enabled.

U21

1

A

pin

6 is then

high and

U21

1fi

pin

9 is high.

This

produces the TABLET STROBE

signal

on

pin 6

of

U21C.

The

Tablet Sequencer

is

stopped fey

DRBUSY

whenever

a

Hard

Copy

is

being made, or when the

screen

is bein

g

paged. The

sequencer

re-initializes

when

DR-

BUSY

is

no

longer present.

Wait

One-Shot

The

Wait

One-Shot

provides

a

pulse of

approximately

3 ms

duration (one-half of the

tablet cycle), during

which

the Digital

Delay circuit is allowed

to

count.

v0-

Upon receipt

of the first pulse

from pin

5 of

U1

11 A,

the

output of

U21

1

B

is accepted

as

an

input to

U11

1

B,

causing

the

pin

9

output

of U111B

to go high. When

this

happens,

the FIREX

pulse

is generated and output

to

the

tablet

pulser th

rough J231 pin

7. Simultaneously

the X-Y

flip-flop

is

set to the

count

X

condition,

awaiting an

enabling

pulse

from

the

output

of the Digital Delay

portion

of

the

circuitry

to start

counting.

The

Wait

One-shot is fired when

the timing

reference

mark

occurs

in the

FIREX

pulse.

Upon receipt

of

the

second

pulse,

U211

pin

5 goes high, the FIREX

signal

is

disabled,

and the unit enters

the Wait

state until

the

one-

shot has

timed out. The Wait

state.produces a

lowonpin

3

of

U101

A

to

disable the

153

kHz

clock. (Refer

to Digital

X-Counter

The

X-counter

is

a

13-bit counter

comprising

U41B,

U135,

U141,U145,

andthe associated gates.

U41Band

the

first

stage

of

U1

35

(pin

8)

are bypassed via U35A

and

U35D

when

the tablet

size

is strap selected as

small.

This

causes

the

two least

signifi cant bits to be ignored

by

disabling

the

21.08 MHz

clock

(COUNTX), causing the

counter

to

become

an

11-bit counter,

and the counter

overflows

on

2

10+l

counts.

When the

Tablet

Size

is selected

as

large,

the

counter

uses

the

full

13bits and Xoverflow

occurs on

3841

counts.

The count

occurs at

the

frequency

of

the

21.08

MHz

clock

that is

gated through

U31A;

each

clock

pulse

repre

sents

0.01 inch of

wav

e

travel

on

the

tablet

wire

grid

X-axis,

TABLET

INITIALIZE

loads

the

X

counter data

outputs

with

zeroes.

5-1

Circuits—

4953/4954

Y-Counter

The

Y-CQunter

is a

13-b*t

counter

comprising

U41

A,

U23S, U251, U151,

and

the associated

gates. While

this

counter

is

truly

a

13-bit up

counter, the outputs are

all

inverted

to

make

it function

as a down counter,

since

the

origin

ofthe

wave

pulse

for the

Y-axis is located at the

top

edge

of the

tablet.

The

down

counter

is. preset with

the

binary

complement ofthe tablet

size,

and counts up

to the

tablet's Y

=

0.

Like the

X-counter, the Y

counter

becomes

an

1

1

-bit

counter

when

the

Tablet

Size strap is

set to small;

when

strapped

for

LARGE, pin

10

of

U151

is

high,

due

to

the

30"

Y-axis

as opposed to the

40"

X-axis

on

the

4954.

U371A

is

latched,

and

the

ARMING

signal

occurs

on

the

pin

5

output

of

.U371A-

Pin

6

of

that

gate then allows

a

TSTROBE

to enter

pin

9 of

U461,

to

latch

bits

1-5

of

the

third

character

in the

command

string

into

U461.

During the

time

that the

Tablet

is arming

for

operation,

the

bus

is not

available.

This

is

due to

U231A,

which

is

sensing LCE,

and the pin

5

output

of arming

latch

U371

A.

Note

that

each time the

tablet

is

armed,

the Delay

One-

shot

fires.

This causes

the

DATA

indicator

on the

Power

Module

to

blink

momentarily.

The

Y axis counter is loaded

to the complement

of

3072

for the large

origin and the

complement

of 1024

for the

small

origin. When counting, the

Y counter

c

ounts

the

"

21 .08

MHz

c

lock that is gated

through

U31C.

TABLET

INITIALIZE

presets the

counter with

the ones

complement

of

3072

for large origin

or the

complement

of 1024 for

small

origin.

Digital

Delay

The

Digital Delay

portion of the

circuit

Is

made

up

of

two 4-bit

counters

(U301

and

U31

1)

forming

a single

8-bit

counter

between

them.

Its

purpose is

to

provide a

digitally-

regulated

delay between

the

time

the

X

or

Y pulser

is fired

and

the time

a

valid DONE

signal from

the

pen preamp

can

±>e accepted,

due to DONE signals

thaioccur as

the pulser

fires. In the

quiescent state, it

is preset

to all

zeroes

when

the

parallel

load

signal on

pin 1

of

U301 and

U311 is

triggered by

the

Wait

One-shot.

The exception

occurs

when

a high

on

OFFSET

is input

on

J231 pin

5 (present

when the

cursor

is

used; not

present

with the

pen).

In

the

case

where

OFFSET is

present,

a one is

loaded into

the bit

4

position

(pin 11 of

U301);

this

represents

an

offset

of

8

counts.

When the Wait

One-shot is

fired,

the counters

are

released

to

count at 21.08 M

Hz

from their

preset value

(zero or

eight), if

a

DONE

pulse

occurs prior

to

the

COTrr

Ptettorc °f

tne

128-count

Digital Delay,

it is

ignored. If

the DONE

pu

lse occurs

during

the

next 96 counts,

UNDERFLOW

is

asserted,

indicating

that

the

pen

is

too

far

to

the left

or top of the

tablet

surface

to

be considered

in

presence.

The counters

count until

pins

2, 9,

and 12 of

U31

1

are

all

high—

a

count

of

224

-At that

time the

RS

flip-

flop formed by

U221C

and U221D is

set and the

COUNT

ENABLE flip-flop

U131A

is set,

beginning

the

X

count.

Address Decoder

The Address

Decoder

located

i n

U451 senses BITS

1-7

on

the

terminal bus in

addition

to

BTSUP

and LCE. When

the ESC character

is

transmitted,

LCE

goes

high

and

remains high

until after

the following

character

is receiv-

ed.

The

ESC ! sequence

is

thereby

decoded

in this

one

gate.

When this

two-character

sequence,

is detected,

Transmit

Enable

When

the

tablet

is

armed,

regardless

of arming

for

multiple

or single

point,

U401

A

is

latched. In single

point,

MULT

! is

pr

esent on pin

5 of

U41

1

B.

After

each

coordinate

point, FREE is output

from

pin

6 of

U1 65B,

enabling

U41 1

B

toreset

U401A after the

first

coordinate

point.

If

the

Tablet

was armed for

Mu

ltiple

Point,

pin

5

of

U41

1 B remains

low,

preventing FREE

from

causing

a

reset; Multiple

Point

transmission

is

then

allowed.

In

addition, the Delay

Control

circuitry

determines

how

much

delay occurs

between

points, when

delay is

strapped

in.

This is

accomplished

by one-shot

U85A, in

conjuction with

potentiometer

R92,

which delays the

READY

signal when delay

is

strapped

in.

ESUP

Whenever

the

tablet

is

armed,

U401 B is set.

Pin

9

then

enables

the ESUP

gate

U275B

to

suppress characters that

do

not

occur in

conjunction

with

the

outputs

of

the Tablet

Sequencer,

effectively

sup

pressing

echoed

data from

being displayed

(via

TSUP).

There

are

eight

exceptions

(echoed characters

which

do

not

get

suppressed); these

are listed

in Section

3

in the

description

of the ESUP

Strappabie

Option.

Transmit Initiate

This circuit

consists

of U61B,

U261B,

U261C, U361C

and U85B.

When the tablet

is armed

to

send on

presence,

the

logic

gate

s

in that

block

dete

rmines that CLEAR TO

GO

i s high,

a

TABLET

STROBE

is

received

from U21C,

and

KLOCK

is not

present.

When

these conditions

are

true,

GO one-shot

U85B

fires,

producing

a

high

on pin 6

of

U175B.

This is input

to

pin

8

of

U475,

which is the" clock

input

of

the character

identifier.

Since

no

data was

in

transfer

at this

point (the

beginning

of

a coordinate

cycle),

a

high

is

clocked

into

the

first

position of the

serial

input

of

U475 (pins

1 and

2),

This

starts

the

Character

Identifier-'-

sequence

in

U475 (see

Character

Identifier.)

5-2

@

Circuits—

4953/4954

c

Output

Sequencer

The

Output

Sequencer

generates

the

bus

strobes,

and

is

enabled

by

ahigh on

pin

6

of

U381

A,

whictiisinput

to

pin

2

of

U165A.

This

clocks

a

high

into

U285B.

The

next

614

kHz

clock

pulse

that

occurs

clocks

this

high

into

U385B

pin

9.

The

fourth

4.9

MHz

clock

pulse to

occur

is

output

from

the

divide-by-four

circuit

comprising

U491A

and

U491B,

and

clocks

the

high

from

U395B

pin

9

into

U485B

pin

9. Pin

10

of

U485B

then

resets

U385B.

The

next

four

4.9

MHz

clock

pulses

into

the

divide-by-four

circuit

cause

another

pulse

to

occur

on

pin

12

of U491,

clocking

the

one

from

U485B

into

U485A.

Two

4.9

MHz

pulses

later,

the

one

is

clocked

into

U385A.

As

the

above

output

pulses

occur,

they

are

input

to

U381B.

The

presence

of

any

of

these

signals

causes a

DATA

OUT

pulse,

which

is

then

input

to

pin

3

of

U465B

and

other

data

bits.

This

same

signal,

which

is

an output

of

U381B,

is

fed

back

into

pin 8

of

U481C

to

prevent

any

other

sequence

to

be

started

while

this

sequence

is

in

progress.

The

pin

9

output

of

U485B

is

used

to

enable

bus

strobes.

Through

U281

D

and

U42

1C,

each

output

of

U485B

pin 9

generates

a

CSTROBE:Through

U281D

and

U281

B,

this

same-output

en

able

s

the C

haract

er

Identifier

to

seque

ntially

send

HIY,

L

OY,

HIX, LO

XE,

and

END-

COUNT

signals

along

with

TSTROBEs,

when

LOCAL

DISPLAY

is

true on

pin

2

of

U461.

Character

identifier

The

Character

Identifier

consists

of

U475,

which

works

in

conjunction

with

the

Strobes

Out

circuitry

and the

Output

Sequencer.

When

a

GO

pulse

is

received

on

pin

4

of U175,

no

data

is being

sent;

SENDING

(U381

A,

pin

6)

is

therefore

low.

That

signal

is

inverted

through

U265A,

and

a

high

is

clocked

into

the

serial

inputs

of

U475.

This

high

immediately

causes

a

high

on

pin

3

of

U475,

causing

U381A

to

output a

high,

which

then

returns

through

U265Ato

place

a

low

in

the

next

input

position

(pins

1

and

2

of U475).

This

low

will

not

be

accepted

until

another

clock

pulse is

received

on

pin

8

of U475.

The

high

in

the

Character

Identifier,

which

is

now

on

pin 3

of U475,

will

move

through

the

output

positions

of

U475

with

each

clock

pulse

in

the

following

order—

pin

3,

pin

4,

pin

5,

pin

6,

pin

10,

pin

11,

pin

12/Each

of

those

outputs

serves

to

identify

which

character

is

being

strobed

onto

the

bus

from

the

tablet,

through

the

Terminal

Strobes

bus

circuitry.

The

first

clock

input,

which

strobed

the

high

into

U475,

occurs

when

GO

occurs

on

pin

12

of

U85B.

Subsequent

clock

pulses

are

generated

by

pin

6

of

U385A,

after

each

cycle

of

the

output

sequencer.

Note

that

when

the

XLOY

position

is

true,

and

10

bit

operation

has

been

signalled

by

the

third

character

in

the

Cont

rol

Co

mmand

sequence

(pin 7

of U461),

the

CSTROBE

for

the

XLOY

~

byte is

disabled,

andthat

byte

does

not

appear

on

the

bus.

When

the C

haracter

Ide

ntifier

passes

through

the

last

position

(LOX—

pin

11),

the

LOXE

byte

is

strobed

onto

the

bus.

If the

peri's

path

is

being

displayed

on

the

termi

nal

screen;

the

GSheaderoharacter

wil l have

s

et the

GRAF

on

theterminal

bus

line

true

(low),

a

nd

LOX

E is

the

last

signal

strobed

onto

the

bus.

However,

if G

RAF

is

high,

it

enables

U465

C,

causing

an

ENDCOUNT

to

occur

immediately

after

LOXE to

disable

the

display.

Output

Shift

Registers

The

Output

Shift

Registers

are U351

,

U335,

U345,

U341

,

and U331.

The

coordinate

data

point,

which

is

generated

in

the

X

and

Y

counte

rs,

is

l

atched

into

the

Output

Shift

Registers

with a

LOAD

pulse.

LOAD

is

output

from

U291

B,

pin

6,

and

can

only

occur

after a

TABLET

STROBE

has

occurred,

indicating

a

valid

data

point

The

output

of

the

X and

Y

counters,

along

with

the

appropriate

Header,,

is

latched

into

the

inputs

of

the

Shift

Registers on

the

following

pins:

pin

6—

-Header,

pin

5—

HIY,

pin

4—

XLOY,

pin

3—

LOY,

pin

14—

HIX,

pin

13—

LOX,

and

pin

12—

CE.

When

the

Shift

Registers

are

loaded,

and

when

the

HEADER

output

of U475

(pih

3)

is

high,

the

conditions

of

bits

1-5

of

the

header

character

are

latched

into

their

positions

(pin

6)

of

the

Shift

Registers.

The

bits

are

defined

as

follows:

Bits

1

and

3

are

high

for

GS

and US,

low

for SUB

and

:,

as

defined

by

the

output

state

of U261

A.

Bit

2

is

low

for

GS

and

high

for

other

characters,

as

defined by

the

output

state

of

U261

D.

Bit

4 is

tied

high;

Bit

5

is

tied

high

for

control

characters

and

low

for

letter

headers,

as

defined

by

the

HEADER

strap.

Bit

7 is

the

inverse

of

bit

5,

and

is

defined

by

the

HEADER

strap

and

U431B.

Bit

6

is low

for

GS,

US,

and

SUB,

but

high

for

the

rheader

character.

This

bit

is

determined

by

the

pin

4

input

of

U365B,

which

is

determined

by

the

pin

ToutputofU481

A.

This

is

normally

low

when

sending

a

Header

or

a

CR.

However,

when

the

:

header

character

is

sent,

no

data

is

being

transmitted

and

the

HEADER

line

is

low,

causing

a

high

input

to

pin

4

of

U365B,

This

causes

bit

6 to

be

true

(low)

as

it

is

placed

on

the

bus.

(Ftecail

that

the

terminal

bus

operates

on-negative

logic.)

When

the

Header

Character

is

a

GS

or a

US,

pin

9

of

U345

is

high.

This

is

tie d

back

to

U281A,

which

then

enables

U365D

to

place

a

TSTROBE

on

the

bus

for GS

or

US

Headers.

The

Shift

Registers

then

shift

one

position

when

the

SHIFT

line

goes

high

(U385A,

pin

7),

placing

the

HIY

bite

in

the

output

positions

of

the

Shift

Registers

(pin

9

of

each).

At

the

same

time,

pin

6

of

U385A

clocks

U475,

moving

the

single

high

bit

into

the

HIY

position

(pin

4).

'

This

sequence

occurs

for

each

byte

strobed

onto

the bus.

5-3

Circuits—

4953/4954

Presence

Latch/True

Presence

The

Presence

Latch detects

ail

conditions

under

which

the

pe

n is

considered

to be

out

of

presence;

these are

tabled

UNDERFLOW,

XOVERFLOW

and

YOVERFLOW.

When

the

Graphics

Tablet is initialized,

the

output

of

U221B

(pin

6)

is

hi

gh,

and the pen

js

considered

to

be

in

presence.

The

first

UNDERFLOW

(which

results

from

a

DONE

pulse prior to the tim

ing

out

of

th e Digital

Delay

portion

of

the

circuitry) or OVERFLOW

(which results

from

the

X

or

Y

counters passing their

maximum values)

will cause

an out-of-presence

condition,

indicated by

a

low

on

pin 6 of

U221B.

The

output of the Presence Latch

is input

to

the True

Presence

block on pins

1

and 2 of

U191A. As

long

as

the

presence condition is

true

(1),

the Tablet

Strobe signal

docks

a one onto

pin

5,

which

passes

through

U291A

(when ARMED-B is

also true) and into the

Presence

Status

block placing a high

on pin 12 of

U18TB.

As

soon as the

pen leaves

presence,

a

tow

is applied

to

pins

1 and

2 of

U191 A; this

clears the flip-flop,

and holds

the output

low.

This condition

is

also input

to

the

Presence

Status block

through the same

routing as

the

in

presence

condition.

°en

Status

The Pen

Status

portion of the circuitry

consists of

U1 21 A,

U1

81

A,

U81 A and the associated gates.

U1

21 A is

a

one-shot that debounces

the pulse

from the pen switch

(PEN).

When the pen switch is closed,

a

high

is output

from

pin 13 of U121A, and is

clocked

through

UlSIAand

U81A by the 614

kHz clock.

This

clocking results

in a

1,6

/ys delay

between

the

outputs

of U181 A (pins

5 and

6)

and the resultant

outputs of U81A

(pins 6

and

7),

This

delay allows

U275A to

detect when

the pen has

been up

and

is then pressed (PEN DOWN);and

allows

U375C to

detect when

the

pen

has

been pressed

and is then released

(PEN

UP). When the pen is

out of

presence, the

output of

the

True

Presence latch

holds U121A

cleared.

Crosshair

-

The

Crosshair

circuitryxonsists of U191B and

11171

A,

and

is

active only

when the tablet

is

initialized

while

the

TRUE GIN signal is present, indicating

the

terminal

is in

GIN mode.

When this occurs, a

high

is present

on

pin 12 of

U19TB.

This is clocked into

U191B

when

the

pen is

brought into presence;

this

clocking occurs

on pin

11

of

U191B.This outputs

a high

from pin

9,

into

pins

4

and

1 of

U171A. Then when

the Bus is

Available (pin

2

of

U171

A)

and

the

next

Clear-to-Go pulse occurs (pin

5

of

U171 A),

a

pulse

is output from pin

6 of U171 A into

pin 10

of U285B.

This causes

the Output Sequencer to

begin

sending

the

colon

(:)

header

character.

The

pulse from U171A

is also

input to

U291B, the output

of which

places the

Header

Character circuitry

in

the SUB

configuration.

However,

since

the

Character Identifier circuitry

is

not identifying

this character as

a Header

but rather

as a Data

Character,

the Bit

6

gate is outputting

a

low

(1

),

transforming

the

SUB

to

a

:

(colon)

character.

This

causes the

terminal

to

respond with

the crosshair

intersect

coordinates,

and

causes the crosshair

to disappear.

Pen

Mode

The

Pen

Mode

circuitry

consists

of U75A,

working

in

conjunction

with the

early

portions of the

Transmit Initiate

circuitry (U65A

and

associated

gates). U75A

is preset

when the

pen

is

out

of

presence;

coming

into presence

releases

U75Afrom

the

preset

state. Then,

when

the

pen is

pressed,

U75A is

cleared,

placing a

high from

pin 14 of

U75A into

pin 4 of U65A

and

enabling

a

Tablet Strobe

signal

to

start

the

Transmit

Inititate

by

firing Go

one-shot

U85B. Prior

to

pressing

the pen,

a high

is

present on

U261B

pin

4,

causing the

Tablet

Strobe to

be blocked

(through

U361C)

from starting

an

initiation of transmis-

sion. Note

that

when the

tablet is

armed

for

send on

presence,

the Pen

Mod

e

circuitry has no

eff

ect on

transmission, since

the

SEND ON

PRESENCE signal

enables U261B

regardless

of

the state of U75A

and U65A.

Header

Control

The

Header

Control

portion

of the

circuitry

consists of

U71

A

and

U71B, with associated gating.

The two

outputs

of the

circuit

block are labeled

according

to

the

Header

Character

normally associated with

the

output.

A

high

on

pin

14 of U71A

produces

a

lowGSheaderthrough

U261D,

for

the

first coordinate

p

oint

after

the

pen

is pressed. As

soon

as the

PEN DOWN pulse times

out, the

GS

is clocked

high

by

the

next

LOAD pulse

output

from

U291B,

pin

6.

Subsequent

headers are

preceded

by

the

SUB header

haracter,

which results from

a

high

output

on

pin 11 of

J71B,

through

U261A. When

the

pen is

released,

U71B is

cleared,

resulting

in a low

on

pin

11

,

and

a high

on

pin

3

of

U261 A.The

GS line

remains

tiigh

also; a

high

on

bottt the

SUB

and

GS

lines

results

in

a

US Header

Character.

Comsup

The

Comsup

circuitry

consists of

a strap

option that

determines

when

coordinate

data is

to

be sent to

the

computer.

When Comsup

is strapped

out, atiigh is

applied

to

pin

2 of

U285A.'

The

first Load pulse after that (output

from

U291B)

clocks

the high through U285A, placing a

high on its

Q

output,

pin

5.

This then

enables the Strobes

Out

circuitry

to send

CSTROBES through

U421C.

When

Comsup

is s

trapped

in,

a low

is placed

on

pin 2

of

U285A,

disabling the CSTROBE circuitry.

When

the

pen is

pressed,

a h

igh is placed

on

pin

2

of U285A, enabling

CSTRQBES as

above.

The

flip-flop

remains enabled until

the pen is

released and

the

US

Header

Character

transmis-

sion

is completed.

5-4

@

Circuits—4953/4954

Enq Generator

The

Enq Generator

is

cleared

by

the

Leaving

Presence

pulse, which

is

input

(on

pin

1

of

U271

A)

to the

flip-flop

consisting of

U165C

and

U271

A.

This

allows

the circuitry

to

generate an ENQ

pulse to

be placed on the

terminal bus

when the

other appropriate conditions are ready. These

are that

the

Bus

is Available (U291D,

pin

12),

not

in GIN

Mode

(U171B,

pin

13),

Ctear-to-Go

present

(UT71 B, pin

10).

The

Enq

Generator flip-flop

will then

f[re an ENQ

pulse (U371B,

pin

8)

upon

receipt of the

next GO

pulse

on

U171B,

pin

9.

This causes

the terminal

to

transmit status

to

the computer,

just

as

if

it

had received an Esc Enq

sequence.

frequency spikes in

the

tine voltage supply to

ground

through

one

of the capacitors. R217 serves

to

discharge

the capacitors when

power is not

applied-

Line Voltage Strapping

The

line

voltage strapping

allows the

selection

of

110 or

220 Vac input, with a low and

high

range

in either of

those

voltages. Details regarding

Line

Voltage

ranges,

and strap

selections for those ranges, is

found in Section

3

of

this

manual.

Presence

Status

The

Presence Status

circuitry

consists of

U

181

B,

U81

B,

and

associated

gates.

The

condition

of

whether the pen

is

in

presence

or out

of

presence

is input to U181B

pin

12.

The condition is

then clocked

through

U181B

and

U81B

by

the

614 kHz

terminal clock.

This clocking

results

in a

1.6

/is

delay

between

the

two flip-flops. U275C

can

therefore

determine

when

the pen has

been

but

of

presence

(pin

11)

and

then

enters presence (pin

TO). If pin

9 is

also

high

(Send on

Presence), a

low

output occurs.

i In the

same

fashion,

U375A can

determine

when

the

pen

has

been

in presence

(pin

1

)

and

then

leaves presence

(pin

13),

allowing

it to

output

a

Leaving

Presence

pulse.

Note

that U161D

allows

changing

Presence Status

only

when

Clear-to-Go is

true, to

prevent

changing

status

in the

middle

of

a

coordinate.

CONTROL

BOARD

The

Control

Board

(see

Control Board

Diagram)

contains

circuitry to

provide

+5 V for

the logic

circuitry

contained on

the

Tablet

Control

card and

within the

Power

Module.

Also

provided is

the

180 V

required to

the pulser

to

fire "acoustic"

waves

in

the

X

and

Y

axes

of the

tablet

grid.

In

addition,

strapping

for

the

selectable line voltage

ranges

is

provided

on the

Control

board.

Line Filter

The

Line

Filter

consists

of two

capacitors (C201,

C218)

and one

resistor

(R217).

its function

is to

Shunt

high

Power-on

Relay

When the Graphics

Tablet

POWER

switch is

in the

On

position, a

path to ground is

provided

through

the relay

for

the

terminal's

—15

V,

which

is

sensed on

the

Tablet

Control card.

When the

-15 V

supply is

present,

the

relay

closes

S1

and S2,

providing

power to the

transformer.

When

power is

removed,

diode

CR316

provides a

shunt

path

for the field stored

in

K305

relay coil.

180 V Supply

CR1

21

,

CR1

25,

CR221 ,

CR225

and C235

form a

bridge

rectifier for the

unregulated

180

V supply.

R149

provides a

discharge

path when power

is

removed. Q155

and

Q185,

with their

associated

resistances

and

VR161,

provide a

regulator for the

above supply.

In

normal

operation, the

emitter of Q1 85

will

be at 1

80 V,

and the

base of

Q1

55

will

be

at

approximately 11.6

V. R165

provides base

drive

for

Q185;

Q155

shunts the

excess

current.

If the

current

drawn

by

the

load

(on

the

emitter

of

Q185)

decreases,

the

voltage at this

point has

a

tendency

to

increase.

This

increases

the voltage on

the

base

of Q1

55,

which,

in turn,

increases

the

current drawn

by

its

collector.

This

decreases the

available base

current

for

Q185,

lowering

the voltage on

its emitter.

In

this way,

the

180 V supply

is

regulated. (The circuit

works in

the opposite

way

when

the

load on

the emitter of

Q185

is

increased,

rather

than

decreased.)

VR161 is

a

voltage

reference

that

serves

to

make the action of Q155

independent

of its

emitter

current.

+5 V Regulator

CR5,

CR6,

CR7,

CR8 and C51

form a

bridge

rectifier

for

unregulated

+5 V

supply.

R18

provides a

discharge

path

when power

is

removed.

The

+5 V supply is

regulated

as

follows:

U85

provides an

output

reference

voltage

of

about

+7

Von pin 6. This

voltage

is

divided

down to

about 5

Vby

R86, R89, and

R75

and

fed

back

into pin

5. U85

also senses

the

voltage

output

on pin

4 through

R87

(return from

the

Tablet Control

Card) with

reference to

pin 5. it

then

5-5

Circuits—

4953/4954

adjusts

the

base

drive

for

Q1002

(the

output

of

pin

10) to

maintain

+5

V

on

pin

4

and

to

the

Tablet

Control

Card

regardless

of

load

current

if

the

load

current

on

J236

pins

6

and

7

increases,

the

voltage

across

R55

increases,

making

U85

pin

2

more

positive

with

respect

to

pin

3.

When

this

increase

is

approximately

0.6

V,

U85

current-limits,

decreasing

the

base

drive

to

Q1002.

The

value

of

R55

is

selected

to

cause

current

limiting

to

occur

when

the

+5

V

current

exceeds

approximately

1.5

A.

C419

provides

regulating

action

against

short-duration

load

current

spikes.

C88

provides

a

path

to

stablize

the

high-frequency

response

characteristics

of

U85.

When

power

is

switched

off,

pin

13

is

tied

directly

to

ground

through

the

power

switch,

to

immediately

clamp

the

+5

V

supply,

indepen-

dent

of

the

discharge

of

C51.

The

output

voltage

is

adjusted

by

R89.

R88

between

RVCC

and

+5

V

provides

a

path

for

the

feedback

voltage

in

case

of

a

break

in

the

fiVCC

line

from

the Tablet

Control

Card.

Buffer

Amplifier

The

Buffer

Amplifier

prevents

the

closing

of

the

pen

switch

from

generating

a

signal

in

the

pen's

pickup

coil.

Q413 functions

witty

R

4

11,

and

R409,to

provide

a

switch

buffer

amplifier

for

the

PEN

signal,

provided

whenever

the

pen

switch is depressed.

When

the

PEN

signal

is

not

present

(Pin

8

of the

Preamp

high),

Q41

3

provides

a

high

input

for U415A

and

B.

When

pin

6 of the

preamp

goes

low

(when

the

pen

is depressed),

Q413

is

turned

off

and

the

voltage

on the

inputs

of

U415A

and

U415B

(pins

1,

2,4,

and

5)

falls

below

the

threshold

of

the

gates,

the

outputs

go

low.

This

provides

the

PEN

signal

on J237

pin

5,

and

the

PEN

indicator

LED

current.

U415C

buffers

the

offset

signal

from

the

preamp

before

it

is

transmitted

to the

Tablet

Control

Card.

U415D

buffers

the

DONE

signal

from

the

preamp.

It

is

then

applied

to

pin

2

of

U421

A,

and

to

U421

D,

an

inverter.

Since

pin

2

of

U421

A

is

already

low

(in

its

quiescentstate),

the

output

of

U421A

goes

high,

to

be

inverted

through

U421B,

producing

a

low

output

The

low

output

remains

only

until

C412

charges,

producing

a

high

on

pin

2 of

U421

A.

This

circuitry

produces

a

low

pulse

on

the

falling

edge

of the

pen

input,

when

that

input

goes

low

and

stays

low.

5-6

@

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(PESJ

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