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I have had some mystery with when I program the EPCS with my programming cable
as to whether I need to remove the programming cable to allow the FPGA configuration
to start. Sometimes I can leave it in. Sometimes I have to disconnect it (?).
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The AS header has nCONFIG and nCE pins. When AS programming starts, the USB-Blaster takes nCONFIG low and nCE high, which resets the FPGA, and tri-states the EPCS bus so the cable can drive the EPCS pins to program it. The USB-Blaster then leaves nCE high. Ideally it would drive nCE low at the end of programming, but that is not always what happens, eg., under Linux its different than under Windows.
Cheers,
Dave
Honored Contributor
