Xilinx Spartan 3 JTAG issues

Hi, I have a XC3S400 based design with an XCF02 and I am finding I can't program the FPGA unless I power cycle it first. If I program the XCF02 it works fine - I'd rather program the FPGA for testing though, it's quicker for a start :)

I am not really sure where to start since I designed the board myself (although it is closely based on the Memec 3SLC eval board we have), I am using XC3Sprog (because I don't actually run Linux), and I am an FPGA noob :)

Any hints or suggestions gratefully received.

Thanks.

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Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
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Daniel O'Connor
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There have been some issues with PlatformFlash and Spartan series parts. This usually crops up when your Spartan is behind the XCFxxS in the JTAG chain. If there is a valid bitstream in the XCFxxS part it is possible that the FPGA will start to configure from it during the JTAG programming operation. To see if this is your problem, see if you can program the FPGA directly via JTAG if you first erase the XCF02S.

HTH, Gabor

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Gabor

Is the config prom getting left in an odd JTAG state? Can you isolate it from the chain?

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Ben Jackson AD7GD

http://www.ben.com/
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Ben Jackson

Hmm not without surgery :)

You are suggesting the flash chip is doing something odd and preventing the FPGA from being programmed? I can probably bypass it without too much hassle for testing purposes..

The odd thing is that I can program the flash chip 100% reliably, but I can only program the FPGA once per power cycle..

I really need to do some testing with Impact to see if it's a problem with xc3sprog.. I would try

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but I'm using FreeBSD and it doesn't emulate Linux's USBFS (yet :)

As Gabor suggested I will try erasing the flash and see how I go as well.

The flash is closest to TDI in this design - it could be swapped around for the production run but in that I'd mostly be programming the flash only so it's a bit of a moot point :)

Thanks for the help.

--
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
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Daniel O'Connor

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