APPENDIX A MIPS III INSTRUCTION SET DETAILS
Preliminary Users Manual S15543EJ1V0UM 503
LBU Load Byte Unsigned LBU
base

LBU

1 0 0 1 0 0 rt offset

31 26 25 21 20 16 15 0
655 16
Format:
LBU rt, offset (base)
Description:
The 16-bit
offset
is sign-extended and added to the contents of general register
base
to form a virtual address.
The contents of the byte at the memory location specified by the effective address are zero-extended and loaded
into general register
rt
.
Operation:
32 T: vAddr ((offset15)16 || offset15..0) + GPR [base]
(pAddr, uncached) AddressTranslation (vAddr, DATA)
pAddr pAddrPSIZE - 1..3 || (pAddr2..0 xor ReverseEndian3)
mem LoadMemory (uncached, BYTE, pAddr, vAddr, DATA)
byte vAddr2..0 xor BigEndianCPU3
GPR [rt] 024 || mem7 + 8* byte..8* byte
64 T: vAddr ((offset15)48 || offset15..0) + GPR [base]
(pAddr, uncached) AddressTranslation (vAddr, DATA)
pAddr pAddrPSIZE - 1..3 || (pAddr2..0 xor ReverseEndian3)
mem LoadMemory (uncached, BYTE, pAddr, vAddr, DATA)
byte vAddr2..0 xor BigEndianCPU3
GPR [rt] 056 || mem7 + 8* byte..8* byte
Exceptions:
TLB refill exception
TLB invalid exception
Bus error exception
Address error exception