SDF sim failure: 8.2i/Spartan-3

Anyone happen to know if there are any problems with sdf simulation for Spartan-3? This works a lot of the time for me, but I get occasional setup failures, with messages like

# ** Warning: /X_SFF SETUP Low VIOLATION ON I WITH RESPECT TO CLK;

Generally, everything else fails soon after a setup violation.

The sdf file doesn't contain any triplets, despite various docs saying that it does. It contains single delay values, which are presumably the maximums. That means that I can't try sdftyp or sdfmax options in the simulator.

What I'm doing is:

- STA passes. I'm driving the device inputs with lots of slack over the worst-case numbers reported by trce

- I'm running netgen with default options on the post-PAR NCD

- sdf options to ModelSim are:

# vsim +no_path_edge +ntc_warn +splitsuh +pulse_int_e/0 +pulse_int_r/0

+multisource_int_delays +transport_int_delays +nowarnTFMPC +pulse_e/0 +pulse_r/0 +sdf_nocheck_celltype +sdf_verbose +transport_path_delays

-quiet -sdfmax /TESTBENCH/DUT=dev_timing.sdf -t ps ...etc.

- XC3S1000-FG676-4, Webpack 8.2i, no service packs

Thanks -

Evan

Reply to
Evan Lavelle
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Any asynchronous signals or clocks in this design?

If this FF is a synchroniser, there is an attribute you can attach to indicate such, so it will not propagate 'X' to the rest of the design (hence the rest failing soon after). Unfortunately I can't remember the attribute.

If not, it could indicate an asynch path that needs a synchroniser.

- Brian

Reply to
Brian Drummond

Wasn't that, but almost as dumb. I forgot that some of my I/Os had explicit pullups in the RTL, and I added keepers in the UCF. The RTL sims worked, but the netlist ended up with keepers instead of pullups, and failed the sims. The sdf stuff all appears to be Ok.

ASYNC_REG

Thanks -

Evan

Reply to
Evan Lavelle

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