722
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 11:
Instruction Set
R
stbux
Store Byte with Update Indexed
Description
An effective address (EA) is calculated by adding an index to a base address, which are
formed as follows:
•
The contents of register
r
B are used as the index.
•
The contents of register
r
A are used as the base address.
The least-significant byte of register
r
S is stored into the byte referenced by EA. The EA is
loaded into
r
A
.
Pseudocode
EA
←
(
r
A) + (
r
B)
MS(EA, 1)
←
(
r
S)
24:31
(
r
A)
←
EA
Registers Altered
•
r
A.
Exceptions
•
Data storage—if the access is prevented by zone protection when data relocation is
enabled.
-
No-access-allowed zone protection applies only to accesses in user mode.
-
Read-only zone protection applies to user and privileged modes.
•
Data TLB miss—if data relocation is enabled and a valid translation-entry
corresponding to the EA is not found in the TLB.
Execution of any of the following invalid-instruction forms results in a boundedly-
undefined result rather than a program exception:
•
Reserved bits containing a non-zero value.
•
r
A
=
0.
Compatibility
This instruction is defined by the PowerPC user instruction-set architecture (UISA). It is
implemented by all PowerPC processors.
stbux
r
S
,
r
A,
r
B
X Instruction Form
31
r
S
r
A
r
B
247
0
0
6
1
1
1
6
2
1
3
1
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