RCA 70/46 - Branch and Link (BALR) (BAL)

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Branch and

Link

(BALR)

(BAL)

General

Description

Format

(RR)

(RX)

Condition Code

Interrupt

Action

Notes

Branching Instructions

•

The

entire

32-bit contents

of

the

P

counter

are

loaded into

the

general

register

specified by R

I

•

Then,

the

program

branches

to

the

instruction

address

specified by

the

branch

address

(R

2

or

X2/B~D2).

The

instruction

length

counter,

the

condition code,

the

program

mask,

and

the

updated

instruction

address

are

stored. However, when

branching

occurs, only

the

instruction

address

is replaced.

(BALR)

05

RI

R2

0

7 8

11

12

15

(BAL)

45

RI

X

2

B2

D2

0

7 8

11

12

15

16

19

20

31

•

Unchanged.

•

None.

• 1.

The

P

counter

is stored

without

branching

in

the

RR

format

when

the

R2

field is zero.

2. When a

branch

occurs,

the

leftmost

eight-bit

portion

of

the

32-bit P

counter

(ILC, CC,

and

mask)

is unpredictable. However,

the

actual

condition code

and

program

mask

(hardware

registers)

are

unaffected

by

branching.

3.

The

contents

of

the

register

specified by

the

second

address

are

unaltered.

4.

The

P

counter

is

moved

to

a reserved

area

in

memory;

the

branch

then

takes

place

as

specified

by

the

contents

of

R2

or

X

2

/B

2

/D

2

•

The

P

counter

(from

the

reserved

area)

is

then

placed

into

Rt.

196

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