Stwbrx - IBM PPC440X5 CPU Core User Manual

Preliminary

stwbrx

Store Word Byte-Reverse Indexed
stwbrx RS, RA, RB
31
0 6
EA (RA|0) + (RB)
MS(EA, 4) BYTE_REVERSE((RS)
An effective address (EA) is formed by adding an index to a base address. The index is the contents of
register RB. The base address is 0 when the RA field is 0 and is the contents of register RA otherwise.
The word in register RS is byte-reversed from the default byte ordering for the memory page referenced by
the EA. The resulting word is stored at the EA.
If instruction bit 31 contains 1, the contents of CR[CR0] are undefined.
Registers Altered
• None
Invalid Instruction Forms
• Reserved fields
Programming Note
Byte ordering is generally controlled by the Endian (E) storage attribute (see Memory Management on
page 133). The store byte reverse instructions provide a mechanism for data to be stored to a memory page
using the opposite byte ordering from that specified by the Endian storage attribute.
instrset.fm.
September 12, 2002
RS RA
11
)
0:31
Store Word Byte-Reverse Indexed
PPC440x5 CPU Core User's Manual
RB
16 21
stwbrx
662
31
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