09-30-2020 07:22 AM
after building a bitstream for a -1 speed grade I can easily check with an additiional timing report, if the same bitstream also matches timing in a -2 speed grade device. However, for a critical design this will most likely reveal some hold time failures for the slow bitstream in a faster device.
Is it possible to let the router optimize timing for both the slower -1 and the faster -2 speed grade? I.e. setup times should be checked against -1 device and hold times against -2 device...?
10-01-2020 12:09 AM
Xilinx will only guarantee operation when the bitstream build matches the device. No other build is supported.
You are absolutely right. But one has to get creative as Xilinx lead times are already exceeding 20 weeks with the US/China trade war having just started.
Being able to run a bitstream on multiple speed grades would allow procurement greater flexibility in buying the chips they can get and not just the ones that have been targeted.
10-01-2020 08:39 AM
10-01-2020 01:19 PM
I think I found a solution: one can simply add more hold slack by adding a "set_clock_uncertainty -hold" constraint. After implementation a manual timing report for the faster speed grade but without the uncertainty constraint should then be run for verification. This can prove the additional hold slack in the design is enough for the slow bitstream to also match hold times of the faster device.
10-01-2020 05:19 PM
This can prove the additional hold slack in the design is enough for the slow bitstream to also match hold times of the faster device.
Don't do this!