MicroBlaze Processor Reference Guide
241
UG081 (v14.7)
Instructions
sb
Store Byte
Description
Stores the contents of the least significant byte of register rD, into the memory location that results
from adding the contents of registers rA and rB.
If the R bit is set, a byte reversed memory location is used, storing data with the opposite endianness
of the endianness defined by
C_ENDIANNESS
and the E bit (if virtual protected mode is enabled).
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 virtual protected mode is enabled, and access is prevented by no-
access-allowed or read-only zone protection. No-access-allowed can only occur in user mode.
Pseudocode
Addr
←
(rA) + (rB)
if TLB_Miss(Addr) and MSR[VM] = 1 then
ESR[EC]
←
10010;ESR[S]
←
1
MSR[UMS]
←
MSR[UM]; MSR[VMS]
←
MSR[VM]; MSR[UM]
←
0; MSR[VM]
←
0
else if Access_Protected(Addr) and MSR[VM] = 1 then
ESR[EC]
←
10000;ESR[S]
←
1; ESR[DIZ]
←
No-access-allowed
MSR[UMS]
←
MSR[UM]; MSR[VMS]
←
MSR[VM]; MSR[UM]
←
0; MSR[VM]
←
0
else
Mem(Addr)
← (
rD)[24:31]
Registers Altered
•
MSR[UM], MSR[VM], MSR[UMS], MSR[VMS], if an exception is generated
•
ESR[EC], ESR[S], if an exception is generated
•
ESR[DIZ], if a data storage exception is generated
Latency
•
1 cycle with
C_AREA_OPTIMIZED=0
•
2 cycles with
C_AREA_OPTIMIZED=1
Note
The byte reversed instruction is only valid if MicroBlaze is configured to use reorder instructions
(
C_USE_REORDER_INSTR = 1
).
sb
rD, rA, rB
sbr
rD, rA, rB
1 1 0 1 0 0
rD
rA
rB
0 R 0 0 0 0 0 0 0 0 0
0
6
11
16
21
31
Содержание MicroBlaze
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