182
MicroBlaze Processor Reference Guide
UG081 (v14.7)
Chapter 5:
MicroBlaze Instruction Set Architecture
bri
Unconditional Branch Immediate
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_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_0x8 then
MSR[UMS]
←
MSR[UM]
MSR[VMS]
←
MSR[VM]
MSR[UM]
←
0
MSR[VM]
←
0
bri
IMM
Branch Immediate
brai
IMM
Branch Absolute Immediate
brid
IMM
Branch Immediate with Delay
braid
IMM
Branch Absolute Immediate with Delay
brlid
rD, IMM
Branch and Link Immediate with Delay
bralid
rD, IMM
Branch Absolute and Link Immediate with Delay
1 0 1 1 1 0
rD
D A L 0 0
IMM
0
6
1
1
1
6
3
1
Содержание MicroBlaze
Страница 1: ...MicroBlaze Processor Reference Guide Embedded Development Kit EDK 14 7 UG081 v14 7...
Страница 4: ...MicroBlaze Processor Reference Guide www xilinx com UG081 v14 7...
Страница 8: ...8 www xilinx com MicroBlaze Processor Reference Guide UG081 v14 7 Chapter 1 Introduction Send Feedback...
Страница 262: ...262 www xilinx com MicroBlaze Processor Reference Guide UG081 v14 7 Send Feedback...