TM-1300 Datasheet, PDF (312/533 Pages) NXP Semiconductors – Programmable Media Processor

TM1300 Data Book
dspidualmul
Philips Semiconductors
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
SEE ALSO
dspidualabs dspidualadd
dspidualsub dspiabs
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 [2¹⁵–1..–2¹⁵] (or
[0x7fff..0x8000]) and written into the corresponding halfwords of rdest. All values are signed 16-bit integers.
3
rsrc1
signed
1
0
signed
3
rsrc2
signed
1
0
signed
×
×
Two full-precision
32-bit signed products
3
0
3
0
signed
signed
Clip to [2¹⁵–1..–2¹⁵]
3
rdest
signed
Clip to [2¹⁵–1..–2¹⁵]
1
0
signed
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 rguard is 1, rdest is written; otherwise, rdest is not changed.
EXAMPLES
Initial Values
Operation
Result
r30 = 0x0020010, r40 = 0x00030020
r10 = 0, r30 = 0x0020010, r40 = 0x00030020
r20 = 1, r30 = 0x0020010, r40 = 0x00030020
r50 = 0x80000002, r80 = 0x00024000
r110 = 0x08000003, r120 = 0x00108001
dspidualmul r30 r40 → r60
IF r10 dspidualmul r30 r40 → r70
IF r20 dspidualmul r30 r40 → r100
dspidualmul r50 r80 → r90
dspidualmul r110 r120 → r125
r60 ← 0x00060200
no change, since guard is false
r100 ← 0x00060200
r90 ← 0x80007fff
r125 ← 0x7fff8000
A-26
PRODUCT SPECIFICATION