RCA Spectra 70 - Page 148

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Subtract

Logical

(SLR)

(SL)

General

Description

Format

(RR)

(RX)

Condition Code

Interrupt

Action

Notes

Fixed-Point

Instructions

•

The

operand

specified by

the

second

address

(R

2

or

XdB

2

/D

2

)

is

logically

subtracted

(32-bit unsigned)

from

the

operand

specified by

the

first

address

(R

1

).

The

difference is placed

in

the

general

register

specified

by

the

first address. The condition code is determined

by

the

relation

of

the

sum

to a zero

number

and

the

occurrence

of

a

carry

out

of

the

sign

bit

position.

An

overflow on such

carries

is

not

recognized

and

does

not

set

an

interrupt

condition.

I

(SLR)

1F

R1

R2

0

7

8

11

12

15

I

(SL)

5F

R1

~2

B2

0

7 8

11

12

15

16

19

• 0 -

not

used.

1-

difference is

not

zero

and

no

carry.

2 - difference is zero

with

a

carry.

3 - difference is

not

zero

with

a

carry.

•

Address

error:

Addressing

(RX

format).

SpecIfication

(RX

format).

20

31

• 1. Logical

subtraction

is accomplished by

adding

the

one's complement

of

the

second

operand

and

a one in

the

low-order position

of

the

first operand.

2.

All 32

bits

of

the

operands

participate

in

the

logical

subtraction

without

change to

the

resulting

sign

bit.

3.

The

operand

specified by

the

second

address

is unaltered.

139

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