Nintendo Ultra64 Programmer's Manual page 178

LBU
31
LBU
1 0 0 1 0 0
6
Format:
lbu rt, offset(base)
Description:
The 16-bit
DMEM address. The contents of the byte at the DMEM location specified by the effective address
are zero-extended and loaded into general register
Since DMEM is only 4K bytes, only the lower 12 bits of the effective address are used.
Operation:
T:
Exceptions:
None
178
Load Byte Unsigned
26 25 21 20
base
5
offset
is sign-extended and added to the contents of general register

16
Addr ((offset ) || offset
15
 (0
24
GPR[rt] || dmem[Addr
31...0
16 15
rt
5
rt
.
) + GPR[base]
15...0
] )
11...0 7..0
LBU
offset
16
base
0
to form a