Appendix B
B-8 MIPS R4000 Microprocessor User's Manual
Figure B-1 shows the I-Type instruction format used by load and store
operations.
Figure B-1 Load and Store Instruction Format
All coprocessor loads and stores reference aligned data items. Thus, for
word loads and stores, the access type field is always WORD, and the low-
order two bits of the address must always be zero.
For doubleword loads and stores, the access type field is always
DOUBLEWORD, and the low-order three bits of the address must always
be zero.
Regardless of byte-numbering order (endianness), the address specifies
that byte which has the smallest byte-address in the addressed field. For
a big-endian machine, this is the leftmost byte; for a little-endian machine,
this is the rightmost byte.
op is a 6-bit operation code
base is the 5-bit base register specifier
ft
is a 5-bit source (for stores) or destination (for loads) FPA register
specifier
offset is the 16-bit signed immediate offset
31 25 21 20 16 0
I-Type (Immediate)
15
offset
26
ftbaseop
655 16
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