Xilinx MicroBlaze Reference Manual page 216

bri Unconditional Branch Immediate
IMM
bri
brai IMM
IMM
brid
braid IMM
rD, IMM
brlid
bralid rD, IMM
1 0 1 1 1 0
0
6
Description
Branch to the instruction located at address determined by IMM, sign-extended to 32 bits.
The mnemonics brlid and bralid will set the L bit. If the L bit is set, linking will be performed. The
current value of PC will be stored in rD.
The mnemonics brai, braid and bralid will set the A bit. If the A bit is set, it means that the branch is
to an absolute value and the target is the value in IMM, otherwise, it is a relative branch and the target
will be PC + IMM.
The mnemonics brid, braid, brlid and bralid 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.
As a special case, when MicroBlaze is configured to use an MMU (C_USE_MMU >= 1) and "bralid
rD, C_BASE_VECTORS+0x8" is used to perform a User Vector Exception, the Machine Status Register
bits User Mode and Virtual Mode are cleared.
Pseudocode
if L = 1 then
←
(rD) PC
if A = 1 then
←
PC sext(IMM)
else
←
PC PC + sext(IMM)
if D = 1 then
allow following instruction to complete execution
if D = 1 and A = 1 and L = 1 and IMM = C_BASE_VECTORS+0x8 then
MSR[UMS]
MSR[VMS]
←
MSR[UM]
←
MSR[VM]
MicroBlaze Processor Reference Guide
UG984 (v2018.2) June 21, 2018
Branch Immediate
Branch Absolute Immediate
Branch Immediate with Delay
Branch Absolute Immediate with Delay
Branch and Link Immediate with Delay
Branch Absolute and Link Immediate with Delay
A L 0 0
rD D
11
←
MSR[UM]
←
MSR[VM]
0
0
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Chapter 5: MicroBlaze Instruction Set Architecture
IMM
16
31
217
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