AR# 4974: 4.1i 4000E MAP - MAP incorrectly trims OUTFFTs that are permanently active.
AR# 4974
4.1i 4000E MAP - MAP incorrectly trims OUTFFTs that are permanently active.
Description
Keywords: XNF, OUTFFT trimmed.
Urgency: Standard
General Description: Pins attached to an OUTFFT with the T tied low (on) in an .xnf file are being trimmed. I cannot simply use OUTFFs, because the design may really be toggling T of OUTFFT.
解决方案
You can work around this problem by placing a "nomerge" attribute on the TBUF control net. This can be done in the .ucf file: