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Hi there Dennis,
First off, sorry for this short mail but we are currently at CeBit so I don't have much spare time.
I was able to track the problem down by trying to configure the FGPA with an old parallel ByteBlaster instead of the USB blaster. This worked fine, so I looked at the difference between their signals. Seems like the overshoot of the USBblaster is too large, so I placed a small capacitor (I think some tens of picofarads, could be more) between TCK and ground.
This completely solved the problem!
Let me know if this works for you as well.
Kind regards,
Riemer Grootjans
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Hi Riemer,
Appreciate your time to post a reply.
I've done exactly following your method but the FPGA still failed to configure. Instead, I have my first 2 PCBs that working fine on both JTAG and AS programming. But my 3 PCBs after that were only able to configure through AS but not JTAG at all. I'm wonder what else will be the cause.
From my observations, the nCONFIG cant be pulled high to VCC (sometimes at the 1.xx V level) when power up the board. CONFIG_DONE has no response at all while downloading through JTAG. nSTATUS sometimes showing a pulse train and sometimes may not.
Both JTAG and AS showing "Info: Configuration succeeded -- 1 device(s) configured" with no error.
Hope you able to enlighten me with other posibble solutions.
Regards,
Dennis
Honored Contributor
