Texas Instruments TMS320C67X/C67X+ DSP - Manual (Page 280)

SMPY Multiply Signed 16 LSB x Signed 16 LSB With Left Shift and Saturation
3-220 Instruction Set SPRU733
Example SMPY .M1 A1,A2,A3
Before instruction 2 cycle after instruction
A1 0000 0123h 291 ‡ A1 0000 0123h
A2 01E0 FA81h −1407 ‡ A2 01E0 FA81h
A3 xxxx xxxxh A3 FFF3 8146h −818874
CSR 0001 0100h CSR 0001 0100h Not saturated
‡ Signed 16-LSB integer