RCA Spectra 70 Training Manual

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COMPARISON

AND

BRANCHING

There

are

two

instructions

that

test

the

relative

value

of two

operands.

The

Compare

Logical

instruction

tests

the

relative

binary

value

of

two

operands.

The

Compare

Decimal

instruction

tests

the

relative

alge-

braic

value

of two

operands

that

are

in

packed

format.

Both

instructions

set

the

Condition

Code

based

on

the

relati

ve

value

of

the

operands.

COMPARE

LOGICAL

(CLC)

INSTRUCTION

The

Compare

Logical

instruction

tests

the

relative

binary

value

of

two

equal-length

operands.

The

two

operands

maybe

in

either

packed

or

unpacked

format.

The

instruction

operates

from

left

to

right

comparing

the

bit

values

in

a

byte

from

each

field.

The

instruc-

tion

terminates

when

either

inequality

is

found

or,

if

both

operands

are

equal

in

value,

when

the

last

byte

in

each

field

has

been

compared.

The

values

of

the

operands

remain

unchanged

in

memory.

Example:

(Comparison

of

Key

Criteria

Fields)

(Character

values

shown)

MACN

HSM

BEFORE

AND

AFTER

EXECUTION

27

28

00

7

00

7

01

5

01

5

02

03

04

8

4

3

TACN

02

03

04

8 4

3

05

1

05

1

ASSEMBLY

INSTRUCTION

OPERAND

06

2

06

2

MACN(8),

TACN

GENERATED

INSTRUCTION

OP

L

B1

D1

B2

I D5

16

I

1

1

10

I

2700

10

110

General

Register

one

contains

0000

07

F

07

D

D2

2800

10

I

CONDITION

CODE

= 2

(FIRST

OPERAND

ffiGH)

Example:

(Comparison

of

Address

Fields)

HSM

BEFORE

AND

AFTER

EXECUTION

ASSEMBLY

INSTRUCTION

ADRI

00

01

20

4007

10

OFA7

16

OPERATION

CLC

ADR2

02

03

20

4017

10

OFBI

1G

OPERAND

I

ADRl(2),

ADR21

37

GENERATED

INSTRUCTION

OP

General

Register

one

contains

0000

CONDITION CODE =

(FIRST

OPERAND

LOW)

COMPARE

DECIMAL

(CP)

INSTRUCTION

The

Compare

Decimal

instruction

tests

the

relative

algebraic

value

of two

packed

operands.

The

oper-

ands

may

be

of

unequal

length.

However,

the

first

operand

should

be

longer

if

the

operands

are

unequal.

lithe

second

operand

is

longer

than

the

first,

the

ex-

cess

bytes

do not

enter

into

the

comparison.

li

the

second

operand

is

shorter

in

length

it

is

assumed

to

contain

high-order

zeros.

The

instruction

operates

from

right

to

left.

As

the

rightmost

half-byte

contains

the

sign,

these

res-

pective

half-bytes

are

compared

first.

If

the

signs

are

unlike,

the

Condition

Code

is

set

to

reflect

the

relative

algebraic

value

of

the

operands

and

the

execution

of

the

instruction

is

terminated.

If

the

signs

are

alike,

the

execution

of

the

instruction

is

terminated

when

the

left~ost

byte

of

the

first

oper-

and

has

been

compared

with

the

actual

(or

zero-ex-

tended)

relatively

positioned

byte

of

the

second

operand.

The

Condition

Code

setting,

in

this

case,

is

also

based

on

the

relative

algebraic

values

of

the

operands.

Example:

HSM

BEFORE

AND

AFTER

EXECUTION

INSTRUCTION

GENERATED

INSTRUCTION

Example:

HSM

BEFORE

AND

AFTER

EXECUTION

INSTRUCTION

AMT

VAL

1024

10

I

General

Register

two

contains

409610

CONDITION

CODE

= 1

(FIRST

OPERAND

LOW)

CHK

BAL

OPERAND

CHK(3), BAL(4)

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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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