Computer Hardware

Spectra 70

RCA Spectra 70 Training Manual

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BINARY

ARITHMETIC

INSTRUCTIONS

In

the

two

binary

arithmetic

instructions,

Add

Binary

and

Subtract

Binary,

the

length

of

both

operands

is

controlled

by

the

length

of

the

first.

As

in

decimal

arithmetic

operations,

if

the

operands

are

unequal,

the

second

operand

is

truncated,

if

longer,

or,

is

extended

with

zero-value

bytes,

if

shorter.

Both

instructions

operate

from

right

to

left.

The

instruction

is

terminated

when

the

left-end

byte

has

been

processed.

The

Condition

Code

Indicator

is

set

based

on

the

result

as

follows:

Condition

Code

Add

Binary

Subtract

Binary

o

Result

is

Zero

Not

Used

I

Difference

Less

Than

Zero

2

Result

is

Greater

Than

Zero

Overflow

I Not

Used

Example:

Assume

an

input

tape

that

contains

a

block

of

five

SO-character

records.

For

processing,

the

programmer

moves

each

record

to

a

separate

processing

area.

The

Add

Binary

in-

struction

increments

the

second

address

of

the

in-

struction

that

moves

a

record

to

the

processing

area.

The

Subtract

Binary

instruction,

with

a

branch

to

read

if

the

input

area

has

been

exhausted,

is

used

to

determine

when

the

last

record

is

processed.

The

Input

Block,

Record

Processing,

and

constant

areas

could

be

allocated

as

follows:

ALLOCATION

OF

INPUT

AND

RECORD

PROCESSING

AREA

NAME

OPERATION

OPERAND

ORG

3000

INP

os

400C

RPR

DS

80C

ORC

RPR

ACCT

DS

8C

NAME

DS

25C

ADR

DS

30C

AMT

DS 10C

FILL

DS

7C

HSM

ALLOCATION

3000-3399

3400-3479

3400-3407

3408-3432

3433-3462

3463-3472

3473-3479

STORED

VALUE

OF

CONSTANTS

(HEX.

FORMAT)

42

ALLOCATION

OF

CONSTANTS

NAME

OPEHATlO'l

OPEHA;-':D

RDIN

DC

A(INP)

:l4RO-:l4R 1

OB

B~

r"CH

DC

A(RO)

00

0,0

TLY

DC

X 'o;iOi) ,

0"

05

CTR

DC

X'O!

'

:l4RG

The

functional

chart

on

the

following

page

shows

the

matching

coding

steps.

Only

the

steps

pertinent

to

the

Binary

Arithmetic

Instructions

are

shown.

Example:

Add

Binary

of

Previous

Instruction

Binary

Value

HSM

BEFORE

AND

AF:TER

EXECUTION

HSM

BEFORE

EXECUTION

ASSEMBLY

INSTRUCTION

GENERATED

INSTRUCTION

HSM

AFTER

EXECUTION

Exercise:

Line

I

Line

2

INCH

34

0000 0000

0101

0000

00

50

0000

1011

1011

1000

OPERAND

IN4+4

(2),

INCR

(2)

OP

L1

L2

B1

D1

Bz

D:2

F6

1

I

1

I

1

10

4016

10

1

10

3482

10

General

Register

one

contains

0000

0000

1100

0000

1000

CONDITION

CODE

= 2

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Reference Manual260 pages

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RCA Spectra 70 Specifications

General

Brand	RCA
Model	Spectra 70
Category	Computer Hardware
Language	English

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