The following error occurs in NGDBuild:
"ERROR:Ngd:284 - %s '%s' , which is the reference clock net for the OFFSET '%s', is not a pad related net (not driven by a pad)."
To prevent this error, ensure that the reference clock in the OFFSET constraint is a pad net.
This error is reported because the OFFSET constraint must be relative to pads, not internal nets.
For OFFSET OUT or OFFSET IN constraints, the relative pads should be the data pad and the clock pad.