Xilinx MicroBlaze Reference Manual page 185

brki
Break Immediate
brki
1 0 1 1 1 0
0 6
Description
Branch and link to the instruction located at address value in IMM, sign-extended to 32 bits. The
current value of PC will be stored in rD. The BIP flag in the MSR will be set, and the reservation bit
will be cleared.
When MicroBlaze is configured to use an MMU (C_USE_MMU >= 1) this instruction is privileged,
except as a special case when "brki rD, C_BASE_VECTORS+0x8" or "brki rD,
C_BASE_VECTORS+0x18" is used to perform a Software Break. This means that, apart from the
special case, if the instruction is attempted in User Mode (MSR[UM] = 1) a Privileged Instruction
exception occurs.
As a special case, when MicroBlaze is configured to use an MMU (C_USE_MMU >= 1) and "brki
rD, C_BASE_VECTORS+0x8" or "brki rD, C_BASE_VECTORS+0x18" is used to perform a
Software Break, the Machine Status Register bits User Mode and Virtual Mode are cleared.
Pseudocode
if MSR[UM] and IMM
else
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.
As a special case, the imm instruction does not override a Software Break "brki rD, 0x18" when
C_USE_DEBUG. is set, irrespective of the value of C_BASE_VECTORS, to allow Software Break
after an imm instruction.
MicroBlaze Processor Reference Guide
UG081 (v14.7)
rD, IMM
rD 0 1 1 0 0
11
≠
C_BASE_VECTORS+0x8 and IMM
←
ESR[EC] 00111
←
(rD) PC
←
PC sext(IMM)
← 1
MSR[BIP]
← 0
Reservation
if IMM = C_BASE_VECTORS+0x8 or IMM = C_BASE_VECTORS+0x18 then
←
MSR[UMS] MSR[UM]MSR[UM]
←
MSR[VMS] MSR[VM]MSR[VM]
rD, unless an exception is generated, in which case the register is unchanged
PC
MSR[BIP], MSR[UM], MSR[VM]
ESR[EC], in case a privileged instruction exception is generated
3 cycles
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IMM
16
≠
←
0
←
0
"imm," page 204 for details on using 32-bit immediate
Instructions
31
C_BASE_VECTORS+0x18 then
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185