Xilinx MicroBlaze Reference Manual page 194

blt
Branch if Less Than
blt rA, rB
bltd rA, rB
1 0 0 1 1 1 D 0 0 1 0
0 6
Description
Branch if rA is less than 0, to the instruction located in the offset value of rB. The target of the branch
will be the instruction at address PC + rB.
The mnemonic bltd will set the D bit. The D bit determines whether there is a branch delay slot or
not. If the D bit is set, it means that there is a delay slot and the instruction following the branch (that
is, in the branch delay slot) is allowed to complete execution before executing the target instruction.
If the D bit is not set, it means that there is no delay slot, so the instruction to be executed after the
branch is the target instruction.
Pseudocode
If rA < 0 then
←
PC PC + rB
else
←
PC PC + 4
if D = 1 then
allow following instruction to complete execution
Registers Altered
• PC
Latency
• 1 cycle (if branch is not taken)
• 2 cycles (if branch is taken and the D bit is set)
• 3 cycles (if branch is taken and the D bit is not set)
Note
A delay slot must not be used by the following: imm, branch, or break instructions. Interrupts and
external hardware breaks are deferred until after the delay slot branch has been completed.
MicroBlaze Processor Reference Guide
UG984 (v2016.2) June 8, 2016
UG984 (v2016.1) April 6, 2016
Chapter 5: MicroBlaze Instruction Set Architecture
Branch if Less Than
Branch if Less Than with Delay
rA rB
1 1
1 6
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0 0 0 0 0 0 0 0 0 0 0
2
1
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3
1
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