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Observer paul.mckechnie
Registered: ‎02-22-2008

Done pin not going high following XCF128X BPI flash configuration

I am currently validating a custom board, which uses a Virtex 5 (XC5VSX95T) and a Xilinx Platform Flash (XCF128X) chip. The Platform Flash is connected to the Virtex 5 such that it uses the BPI interface to program the V5 when the board is powered on. The board is also set up so that I can use the Master SelectMAP mode to configure the V5 should I need to.


I am able to program the Virtex 5 over JTAG without any problems. However, I have a small problem with programming the PROM. I am able to erase the PROM, write to the PROM and verify the PROM contents. However, following a write to the PROM, iMPACT tries to reconfigure the FPGA, which results in an error as the done pin does not go high. There is no option to write to the PROM without reconfiguring the FPGA. I have been able to verify that the done pin has been held low by observing a test point on my oscilloscope.


Strangely, when the board is powered down and subsequently turned back on the FPGA is configured correctly with the new design loaded from the PROM. As I understand, the PROM is configured by iMPACT, which reconfigures the V5 design with a special programming configuration bitstream. This allow iMPACT to communicate through the JTAG chain to the FPGA and then to the PROM using the BPI interface from the FPGA. Obviously, when the PROM has been written to and iMPACT attempts to reconfigure the device with the new image, the configuration bitstream is lost.


Is the done pin expected to remain low and generate an error in this configuration scenario? Or is there a configuration option that I might have missed in iMPACT? Or has the board possibly got a incorrect connection somewhere?


Any advice would be appreciated.





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