I define OFFSET constraints for my I/O timing (OFFSET/IN and OFFSET/OUT), but the tools ignore the constraint and report that my clock does not clock the data specified in my OFFSET constraint. The following warnings appear:
"WARNING:Timing:2664 - SYS_CLK does not clock data from IN_PADS_GRP"
"WARNING:Timing:2666 - Constraint ignored: TIMEGRP "IN_PADS_GRP" OFFSET = IN 7 nS
BEFORE COMP "SYS_CLK" TIMEGRP "IN_FFS" ;"
"WARNING:Timing:2667 - SYS_CLK does not clock data to OUT_PADS_GRP"
"WARNING:Timing:2666 - Constraint ignored: TIMEGRP "OUT_PADS_GRP" OFFSET = OUT 11 nS
AFTER COMP "SYS_CLK" TIMEGRP "OUT_FFS" ;"
SYS_CLK does clock the data that comes in on the pad in group "IN_PADS_GRP," and SYS_CLK clocks out the data that goes to the pads in group "OUT_PADS_GRP." Why do the tools ignore these constraints?
The current warning messages are somewhat unclear. The above messages correctly flag a problem, but it is difficult to see where the actual problem lies. For example, the warnings may reference the PAD group even though the FF group may actually be at fault.
In this case, the PAD group was defined correctly, but the IN_FFS and OUT_FFS flip-flop groups do not contain the correct BELs.