Answers Database
--OBS--M1.3 4kex Timing - Long delays are calculated for TBUFs driving long lines with Pullups.
Record #2741
Product Family: Software
Product Line: FPGA Implementation
Product Part: Timing Analyzer
Product Version: 1.3
Problem Title:
--OBS--M1.3 4kex Timing - Long delays are calculated for TBUFs driving long lines with
Pullups.
Problem Description:
A long delay is calculated for TBUFs driving long lines
with pullups in XC4000EX devices. This is because the tools
are incorrectly defaulting to wired delays when a pullup
is present, rather than the active delay.
Reference # 100471
Solution 1:
Pullups are not recommended for use with active TBUFs because
of the existance of weak keepers on the long lines.
End of Record #2741 - Last Modified: 04/26/99 14:21 |
