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kaz, I'm not sure I really understand your answer.
Say FPGA 1 communicates with FPGA 2.
Now I want to write the I/O constraints for FPGA 1.
For that I need the Tsu and Th of the external device, i.e. FPGA 2.
For these I/O constraints I am supposed to use arbitrary values?
And then look where? The report (of FPGA 2) or the data sheet?
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datasheet here does not mean datasheet as we know it. Once you run timequest you get a report section called datasheet which informs of achieved tSU/tH/tCO
you apply some sensible values on fpga2 input delays (destination device) run project, run timequest and see datasheet report of timequest
Then use that for fpga1 output delay values
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