The following error occurs in NGDBuild:
"ERROR:NgdBuild:467 - %s pad net '%s' has an illegal buffer. Xvendor=%s Xleid=%d Xhiername=%s"
To prevent this error from occurring, make sure that the pad and buffer are instantiated and used correctly in your design. This can be caused by the synthesis tool inferring logic that you did not intend. This can also happen when you instantiate a component, which already contains a buffer, and you add a port/buffer in the HDL code.