When I make the readback on the Spartan II concerning a configuration's bitstream which changes the state of some flip flop, the returned bitstream is not the current one but starting bitstream whitout changes.
How are you reading the bitstream? Do you use iMPACT? How do you know the bitstream hasn't changed? Is it your own comparison software or iMPACT "verify"?
If you use "verify" in iMPACT you should realize that the bitstream is masked with the .msk file generated along with the .bit file in your project. Once masked, the resulting verify operation will not compare the bits corresponding to the changing state. It only uses bits such as LUT functions and routing that do not change once the design starts running.
Gabor ha scritto:
Dear Gabor thank you for the info. I do not use "IMPACT" but I have implemented a class library in java for the "readback" using the JTAG TAP . When I read bitstream i obtain the starting bitstream not the actually.
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