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TM1300 Data Book
Philips Semiconductors
A-26
PRODUCT SPECIFICATION
Dual clipped multiply of signed 16-bit halfwords
SYNTAX
[ IF rguard ] dspidualmul rsrc1 rsrc2
→
rdest
FUNCTION
if
rguard
then {
temp1
←
sign_ext16to32(rsrc1<15:0>)
×
sign_ext16to32(rsrc2<15:0>)
temp2
←
sign_ext16to32(rsrc1<31:16>)
×
sign_ext16to32(rsrc2<31:16>)
if
temp1 < 0xffff8000
then
temp1
←
0x8000
if
temp2 < 0xffff8000
then
temp2
←
0x8000
if
temp1 > 0x7fff
then
temp1
←
0x7fff
if
temp2 > 0x7fff
then
temp2
←
0x7fff
rdest<31:16>
←
temp2<15:0>
rdest<15:0>
←
temp1<15:0>
}
ATTRIBUTES
Function unit
Operation code
Number of operands
Modifier
Modifier range
Latency
Issue slots
dspmul
95
2
No
—
3
2, 3
DESCRIPTION
As shown below, the
dspidualmul
operation computes two 16-bit clipped, signed products separately on the two
pairs of high and low 16-bit halfwords of rsrc1 and rsrc2 Both products are clipped into the range [2
15
–1..–2
15
] (or
[0x7fff..0x8000]) and written into the corresponding halfwords of rdest All values are signed 16-bit integers.
The
dspidualmul
operation optionally takes a guard, specified in rguard If a guard is present, its LSB controls the
modification of the destination register. If the LSB of rguardis 1, rdestis written; otherwise, rdestis not changed.
EXAMPLES
Initial Values
Operation
Result
r30 = 0x0020010, r40 = 0x00030020
r10 = 0, r30 = 0x0020010, r40 = 0x00030020
IF r10 dspidualmul r30 r40
→
r70
r20 = 1, r30 = 0x0020010, r40 = 0x00030020
IF r20 dspidualmul r30 r40
→
r100
r50 = 0x80000002, r80 = 0x00024000
dspidualmul r50 r80
→
r90
r110 = 0x08000003, r120 = 0x00108001
dspidualmul r110 r120
→
r125
dspidualmul r30 r40
→
r60
r60
←
0x00060200
no change, since guard is false
r100
←
0x00060200
r90
←
0x80007fff
r125
←
0x7fff8000
0
1
3
rsrc1
0
1
3
rsrc2
0
3
rdest
×
×
1
0
3
0
3
Two full-precision
32-bit signed products
Clip to [2
15
–1..–2
15
]
Clip to [2
15
–1..–2
15
]
signed
signed
signed
signed
signed
signed
signed
signed
SEE ALSO
dspidualabs dspidualadd
dspidualsub dspiabs
dspidualmul