Texas Instruments TMS320C67X/C67X+ DSP - Manual (Page 80)

Resource Constraints
Instruction Set 3-20 SPRU733
3.7 Resource Constraints
No two instructions within the same execute packet can use the same
resources. Also, no two instructions can write to the same register during the
same cycle. The following sections describe how an instruction can use each
of the resources.
3.7.1 Constraints on Instructions Using the Same Functional Unit
Two instructions using the same functional unit cannot be issued in the same
execute packet.
The following execute packet is invalid:
ADD .S1 A0, A1, A2 ;.S1 is used for
|| SHR .S1 A3, 15, A4 ;...both instructions
The following execute packet is valid:
ADD .L1 A0, A1, A2 ;Two different functional
|| SHR .S1 A3, 15, A4 ;...units are used
3.7.2 Constraints on the Same Functional Unit Writing in the Same Instruction Cycle
Two instructions using the same functional unit cannot write their results in the
same instruction cycle.