Branch And Link (Balr) (Bal) - RCA 70/46 Reference Manual

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