Calculate CRC in Virtex-Spartan II bitstream

Francesco Verdicchio schrieb:

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Franseso,

the bitstream CRC calculation works as described in Xilinx docs. So yes if you cant calculate it properly then you have made an error and you must resolve the problem you have.

each write to CRC register clear the CRC so it restarts again. also check that you have proper bit-order in the CRC in my algorithm I need todo 16 bit swap, but that depends on how you calculate the CRC.

Antti

I have not gone into the details of CRC for the spartan-II but recently implemented the CRC computation for virtex-II family. Some caveats:

You must compute LSB first on these 36 bits (on virtex-II, there are 5 bits of register address, you may also want to check this).

You must be carefull that the CRC reset happens *after* CRC update by the RCRC command write (which means that after the RCRC command, the CRC register is actually zero, not the weird value computed from the CMD addr + RCRC command).

On virtex-II at least, the contiguous writes to the FDRI must update the CRC taking into account the FDRI address for each word (this is clear from the app notes).

Then, on the Virtex-II at least, a successfull CRC write/check would be:

1/ update the CRC according to the CRC reg addr + CRC write data 2/ check that the resulting CRC value is indeed zero

That is, never access the CRC register's value directly (except on CRC reset), even in the case of a CRC register write...

The autoCRC word (if such a thing exists in the spartanII) must be interpreted as a write to the CRC register (which should zero its value).

JB