Xilinx MicroBlaze Reference Manual page 175

blei
Branch Immediate if Less or Equal
blei
bleid
1 0 1 1 1 1 D 0 0 1 1
0 6
Description
Branch if rA is less or equal to 0, to the instruction located in the offset value of IMM. The target of
the branch will be the instruction at address PC + IMM.
The mnemonic bleid 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
Registers Altered
•
Latency
•
•
•
Note
By default, Type B Instructions will take the 16-bit IMM field value and sign extend it to 32 bits to
use as the immediate operand. This behavior can be overridden by preceding the Type B instruction
with an imm instruction. See the instruction
values.
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
UG081 (v14.7)
rA, IMM
rA, IMM
rA
1
1
If rA <= 0 then
←
PC PC + sext(IMM)
else
←
PC PC + 4
if D = 1 then
allow following instruction to complete execution
PC
1 cycle (if branch is not taken, or successful branch prediction occurs)
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, or a branch prediction mispredict occurs)
www.xilinx.com
Branch Immediate if Less or Equal
Branch Immediate if Less or Equal with Delay
IMM
1
6
"imm," page 204 for details on using 32-bit immediate
Instructions
3
1
175
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