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March 2002 Release
655
Virtex-II Pro™ Platform FPGA Documentation
1-800-255-7778
Alphabetical Instruction Listing
R
lswx
Load String Word 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.
•
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.
Let
n
specify the byte count contained in XER[TBC].
Let
nr
specify the number of registers to load with data.
nr
=
CEIL(
n
÷
4).
Let R
FINAL
specify the last register to be loaded with data.
n
consecutive bytes starting at
the memory address referenced by EA are loaded into GPRs
r
D through R
FINAL
. The
sequence of registers wraps around to
r
0 if necessary. R
FINAL
=
r
D
+
nr
−
1 (modulo 32).
Bytes are loaded in each register starting with the most-significant register byte and ending
with the least-significant register byte. If the byte count is exhausted before R
FINAL
is filled,
the remaining bytes in R
FINAL
are loaded with 0.
If XER[TBC]
=
0, the contents of register
r
D are unchanged and
lswx
is treated as a no-
operation.
Pseudocode
EA
←
(
r
A|0) + (
r
B)
n
←
XER[TBC]
R
FINAL
←
((
r
D + CEIL(n/4)
−
1) % 32)
reg
←
r
D
−
1
bit
←
0
do while n > 0
if bit
=
0
then
reg
←
reg + 1
if reg
=
32
then reg
←
0
if ((reg
≠
r
A)
∨
(reg
=
R
FINAL
))
then (GPR(reg))
←
0
if ((reg
≠
r
A)
∨
(reg
=
R
FINAL
))
then (GPR(reg)
bit:bit+7
)
←
MS(EA,1)
bit
←
bit + 8
lswx
r
D,
r
A,
r
B
X Instruction Form
31
r
D
r
A
r
B
533
0
0
6
1
1
1
6
2
1
3
1
Содержание Virtex-II Pro PPC405
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