AR# 3654: A1.4/F1.4 PAR - Problems with placement of Wide Edge Decoders or associated Pullups.
A1.4/F1.4 PAR - Problems with placement of Wide Edge Decoders or associated Pullups.
The M1 mapper does a poor job of configuring a network of Wide Edge decoders unless it is guided by edge location constraints on all decoder symbols. The symptoms of this problem are placement errors in PAR involving Decoders or their associated Pullups.
Example 1. ERROR:x4kpl:133 - Unable to resolve the placement of all decoder groups in a legal manner. Please check decoder and PULLUP constraints for conflicts.
Example 2. ERROR:x4krt:3 - Pullup on signal "SKIN/MICRO/DECODES/$1N489" is not on same edge of the die as the edge decoder. This is required in order to route the pullup to the output of the edge decoder; the router will terminate.
Wide Decoder Networks are handled well if the mapper is guided by an edge constraint on each decoder symbol.
The following is an example of a .ucf file constraint that puts a LOC constraint on a Decoder symbol: