724
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 11:
Instruction Set
R
sth
Store Halfword
Description
An effective address (EA) is calculated by adding a displacement to a base address, which
are formed as follows:
•
The displacement is formed by sign-extending the 16-bit d instruction field to 32 bits.
•
If the
r
A field is 0, the base address is 0.
•
If the
r
A field is not 0, the contents of register
r
A are used as the base address.
The least-significant halfword of register
r
S is stored into the halfword referenced by EA.
Pseudocode
EA
←
(
r
A|0) + EXTS(d)
MS(EA, 2)
←
(
r
S)
16:31
Registers Altered
•
None.
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.
Compatibility
This instruction is defined by the PowerPC user instruction-set architecture (UISA). It is
implemented by all PowerPC processors.
sth
r
S
, d(
r
A)
D Instruction Form
44
r
S
r
A
d
0
6
1
1
1
6
3
1
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