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MicroBlaze Processor Reference Guide
UG081 (v14.7)
Chapter 5:
MicroBlaze Instruction Set Architecture
lwi
Load Word Immediate
Description
Loads a word (32 bits) from the word aligned memory location that results from adding the contents
of register rA and the value IMM, sign-extended to 32 bits. The data is placed in register rD. A data
TLB miss exception occurs if virtual protected mode is enabled, and a valid translation entry
corresponding to the address is not found in the TLB.A data storage exception occurs if access is
prevented by a no-access-allowed zone protection. This only applies to accesses with user mode and
virtual protected mode enabled. An unaligned data access exception occurs if the two least
significant bits in the address are not zero.
Pseudocode
Addr
←
(rA) + sext(IMM)
if TLB_Miss(Addr) and MSR[VM] = 1 then
ESR[EC]
←
10010;ESR[S]
←
0
MSR[UMS]
←
MSR[UM]; MSR[VMS]
←
MSR[VM]; MSR[UM]
←
0; MSR[VM]
←
0
else if Access_Protected(Addr) and MSR[UM] = 1 and MSR[VM] = 1 then
ESR[EC]
←
10000;ESR[S]
←
0; ESR[DIZ]
←
1
MSR[UMS]
←
MSR[UM]; MSR[VMS]
←
MSR[VM]; MSR[UM]
←
0; MSR[VM]
←
0
else if Addr[30:31]
≠
0 then
ESR[EC]
←
00001; ESR[W]
←
1; ESR[S]
←
0; ESR[Rx]
←
rD
else
(rD)
←
Mem(Addr)
Registers Altered
•
rD, unless an exception is generated, in which case the register is unchanged
•
MSR[UM], MSR[VM], MSR[UMS], MSR[VMS], if a TLB miss exception or a data storage
exception is generated
•
ESR[EC], ESR[S], if an exception is generated
•
ESR[DIZ], if a data storage exception is generated
•
ESR[W], ESR[Rx], if an unaligned data access exception is generated
Latency
•
1 cycle with
C_AREA_OPTIMIZED=0
•
2 cycles with
C_AREA_OPTIMIZED=1
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
for details on using 32-bit immediate
values.
lwi
rD, rA, IMM
1 1 1 0 1 0
rD
rA
IMM
0
6
11
16
31