R

Chapter 4: MicroBlaze Instruction Set Architecture

beqi

Branch Immediate if Equal

 

beqi

rA, IMM

Branch Immediate if Equal

beqid

rA, IMM

Branch Immediate if Equal with Delay

1 0 1 1 1 1

D 0 0 0 0

rA

IMM

0

6

11

16

31

Description

Branch if rA is 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 beqid 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 (i.e. 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 + sext(IMM) 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

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 imm instruction for details on using 32-bit immediate values.

A delay slot must not be used by the following: IMM, branch, or break instructions. This also applies to instructions causing recoverable exceptions (e.g. unalignement), when hardware exceptions are enabled. Interrupts and external hardware breaks are deferred until after the delay slot branch has been completed.

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MicroBlaze Processor Reference Guide

 

1-800-255-7778

UG081 (v6.0) June 1, 2006

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Xilinx EDK 8.2i manual Branch Immediate if Equal Beqi, Beqid