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638
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 11:
Instruction Set
R
lbz
Load Byte and Zero
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 byte referenced by EA is extended to 32 bits by concatenating 24 0-bits on the left. The
result is loaded into register
r
D.
Pseudocode
EA
←
(
r
A|0) + EXTS(d)
(
r
D)
←
24
0 ||
MS(EA,1)
Registers Altered
•
r
D.
Exceptions
•
Data storage—if the access is prevented by no-access-allowed zone protection. This
only applies to accesses in user mode when data relocation is enabled.
•
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.
lbz
r
D, d(
r
A)
D Instruction Form
34
r
D
r
A
d
0
6
1
1
1
6
3
1
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