Branch On Condition (Bcr) (Be) - RCA 70/46 Reference Manual

Branch on Condition
(BCR) (BC)
General Description
Format
(II)
(RX)
Condition Code
Interrupt Action
Notes
Branching Instructions
• If the condition code is set to any of the conditions specified by the
four-bit mask field (M or M
1 ) ,
the P counter is replaced by the branch
address (R
2
or X
2
/B
2
/D
2 ).
If the four-bit mask field (M or Md is not
equivalent to the condition code settings, branching does not occur and
the next instruction in sequence is executed. The branch is initiated when-
ever the condition code has a corresponding mask bit set.
0
0
•
•
•
(BCR)
07
Ml
R2
7 8 11
12 15
(BC)
47
M
X
2
B2
D2
7
8 11
12 15 16 19 20
31
Unchanged.
None.
1. The four-bit mask in
Ml
corresponds, left-to-right, with the four
condition codes:
Instruction Bit Condition Code
8
0
9 1
10 2
11 3
2. If all mask bits are set (M
1
=
F
1G ) ,
an unconditional branch is
effected.
3. When all mask bits are zero, or if R2 in the RR format is zero, the
instruction is a nO-OPe
4. 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.
5. The contents of the registers specified by the second address are
unaltered.
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