MicroBlaze Processor Reference Guide 203
UG984 (v2018.2) June 21, 2018 www.xilinx.com
Chapter 5: MicroBlaze Instruction Set Architecture
beq
Branch if Equal
beq
rA, rB
Branch if Equal
beqd
rA, rB
Branch if Equal with Delay
1 0 0 1 1 1 D 0 0 0 0 rA rB 0 0 0 0 0 0 0 0 0 0 0
0 6 11 16 21
31
Description
Branch if rA is equal to 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 beqd 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.
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