Texas Instruments TMS320C67X/C67X+ DSP - Manual (Page 294)

SSUB Subtract Two Signed Integers With Saturation
3-234 Instruction Set SPRU733
Subtract Two Signed Integers With Saturation SSUB
Syntax SSUB (.unit) src1, src2, dst
.unit = .L1 or .L2
Compatibility C62x, C64x, C67x, and C67x+ CPU
Opcode
31 29 28 27 23 22 18 17 13 12 11 5 4 3 2 1 0
creg z dst src2 src1 x op 1 1 0 s p
3 1 5 5 5 1 7 1 1
Opcode map field used... For operand type... Unit Opfield
src1
src2
dst sint
xsint
sint .L1, .L2 000 1111
src1
src2
dst xsint
sint
sint .L1, .L2 001 1111
src1
src2
dst scst5
xsint
sint .L1, .L2 000 1110
src1
src2
dst scst5
slong
slong .L1, .L2 010 1100
Description src2 is subtracted from src1 and is saturated to the result size according to the
following rules:
1) If the result is an int and src1 − src2 > 2 31 − 1, then the result is 2 31 − 1.
2) If the result is an int and src1 − src2 < −2 31 , then the result is −2 31 .
3) If the result is a long and src1 − src2 > 2 39 − 1, then the result is 2 39 − 1.
4) If the result is a long and src1 − src2 < −2 39 , then the result is −2 39 .
The result is placed in dst. If a saturate occurs, the SAT bit in CSR is set
one cycle after dst is written.
Execution if (cond) src1 −s src2 → dst
else nop