RCA 70/46 - Branch on Index Low or Equal (BXLE)

Branch on Index
low or Equal
(BXlE)
General Description
Format
(RS)
Condition Code
Interrupt Action
Notes
Branching Instructions
• The operand specified by the third address (R
3
)
is added to the operand
specified by the first address (R
1
)
and the sum is algebraically compared
with the operand specified by the third address (R
3
), if R3 specifies an odd
register. If R3 specifies an even register, the sum is algebraically compared
with R3 + 1. If the sum is high, branching does not occur and the next
instruction in sequence is executed. If the sum is low or equal, the
instruction address in the P counter is replaced by the branch address
(B
2
/D
2
)
and branching occurs.
o
7 8 11 12 15 16 19 20 31
• Unchanged.
• None.
• 1. The sum replaces the operand specified by the first address (R
1
)
regardless of the comparison. The sum replaces (R
1
)
after the
comparison has been made.
2.
Overflow is not recognized.
3. The contents
of the register specified by R3 or R3 + 1 are unaltered.
4.
When a branch occurs, the leftmost eight-bit positions of the 32-bit
P counter (ILC, CC, and mask) are unpredictable. However, the
actual condition code and program mask (hardware registers) are
unaffected by branching.
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