Texas Instruments TMS320C67X/C67X+ DSP manual Intdp

	Resource Constraints
MPYDP	No other instruction on the same side can use the cross
	path on cycles i, i + 1, i + 2, and i + 3.
MPYSPDP	No other instruction on the same side can use the cross
	path on cycles i and i + 1.

Other hazards exist because instructions have varying numbers of delay slots, and need the functional unit read and write ports of varying numbers of cycles. A read or write hazard exists when two instructions on the same functional unit attempt to read or write, respectively, to the register file on the same cycle.

An instruction of the following types scheduled on cycle i has the following constraints:

2-cycle DP	A single-cycle instruction cannot be scheduled on that
	functional unit on cycle i + 1 due to a write hazard on cycle
	i + 1.
	Another 2-cycle DP instruction cannot be scheduled on
	that functional unit on cycle i + 1 due to a write hazard on
	cycle i + 1.
4-cycle	A single-cycle instruction cannot be scheduled on that
	functional unit on cycle i + 3 due to a write hazard on cycle
	i + 3.
	A multiply (16 ⋅ 16-bit) instruction cannot be scheduled
	on that functional unit on cycle i + 2 due to a write hazard
	on cycle i + 3.
ADDDP/SUBDP	A single-cycle instruction cannot be scheduled on that
	functional unit on cycle i + 5 or i + 6 due to a write hazard
	on cycle i + 5 or i + 6, respectively.
	A 4-cycle instruction cannot be scheduled on that func-
	tional unit on cycle i + 2 or i + 3 due to a write hazard on
	cycle i + 5 or i + 6, respectively.
	An INTDP instruction cannot be scheduled on that func-
	tional unit on cycle i + 2 or i + 3 due to a write hazard on
	cycle i + 5 or i + 6, respectively.
INTDP	A single-cycle instruction cannot be scheduled on that
	functional unit on cycle i + 3 or i + 4 due to a write hazard
	on cycle i + 3 or i + 4, respectively.
	An INTDP instruction cannot be scheduled on that func-
	tional unit on cycle i + 1 due to a write hazard on cycle
	i + 1.
	A 4-cycle instruction cannot be scheduled on that func-
	tional unit on cycle i + 1 due to a write hazard on cycle
	i + 1.

SPRU733 Instruction Set 3-27