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March 2002 Release
665
Virtex-II Pro™ Platform FPGA Documentation
1-800-255-7778
Alphabetical Instruction Listing
R
macchwsu
Multiply Accumulate Cross Halfword to Word Saturate Unsigned
Description
The low-order halfword of
r
A is multiplied by the high-order halfword of
r
B. The
unsigned product is added to the contents of
r
D and the sum is stored as a 33-bit
temporary result.
If the result does not overflow, the low-order 32 bits of the temporary result are stored in
r
D. If the result overflows,
r
D is loaded with the nearest representable value. If the result is
greater than 2
32
−
1, the value stored in
r
D is 2
32
−
1. An example of this operation is shown
Pseudocode
prod
0:31
←
(
r
A)
16:31
×
(
r
B)
0:15
unsigned
temp
0:32
←
prod
0:31
+ (
r
D)
(
r
D)
←
(temp
1:32
∨
32
temp
0
)
Registers Altered
•
r
D.
•
CR[CR0]
LT, GT, EQ, SO
if Rc
=
1.
•
XER[SO, OV] if OE
=
1.
Exceptions
•
None.
Compatibility
This instruction is implementation specific and is not guaranteed to be supported by other
PowerPC processors.
macchwsu
r
D,
r
A,
r
B
(OE=0, Rc=0)
macchwsu.
r
D,
r
A,
r
B
(OE=0, Rc=1)
macchwsuo
r
D,
r
A,
r
B
(OE=1, Rc=0)
macchwsuo.
r
D,
r
A,
r
B
(OE=1, Rc=1)
XO Instruction Form
4
r
D
r
A
r
B
OE
204
Rc
0
6
1
1
1
6
2
1
2
2
3
1
Содержание Virtex-II Pro PPC405
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