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TRCE/Timing Analyzer 2.1i: 0 items analysed on OFFSET constraints in Virtex designs on ofd/ifds
Record #7131
Problem Title:
TRCE/Timing Analyzer 2.1i: 0 items analysed on OFFSET constraints in Virtex designs on
ofd/ifds
Problem Description:
Urgency: Standard
Problem description:
When using OFFSET constraints on an output pad that has
both the tri-ff in a particular IOB and the out-ff in the same
IOB, then to be able to apply different OFFSET constraints
to the different flip flops.
The normal method would be to create a timegrp for the tri-ffs
and another for the out-ffs and then to apply different OFFSET
constraints to the different groups. However, when both the
tri-ff and the out-ff go into the IOB, the OFFSETconstraints are
ignored.
(0 items analysed).
However, if one of those flops is moved into a CLB, then one
of the OFFSET constraints is analysed properly and it is
ALWAYS the one associated with the flop that has just been
moved into the CLB. In the trce report, the other OFFSET
constraint is still listed as 0 items analysed.
AND
When using an OFFSET constraint on an input pad which
feeds the data input of two flip-flops which are clocked by
different clocks. It is desirable to apply differerent OFFSET
constraints to these flops. The normal method would be to
create 2 timegrps, one for the flops clocked by CLK1 and
one for the flip flops clocked by CLK2. Then create 2
separate OFFSET-IN constraints.
Both give 0 items analysed in the trce report.
Solution 1:
Another workaround is to do a detailed report with just
the tri-ff to pad path, then do another detailed report
with just the out-ff to pad path.
Solution 2:
The workaround is to create a detailed timing report, it is
possible to find the paths through the flops situated
in the IOBs and perform the calculations manually.
End of Record #7131 - Last Modified: 10/25/99 14:44 |
