iMPACT downloading error

Hello Byung,

I haven't looked at the specifics of that board but here are a few general things to try:

1) What speed do you have the cable configured to run at? Try a slower speed if possible. If you have a signal integrity issue this will help but it will take longer. 2) There are some Xilinx devices (like some Spartan 3) that have a bug in the readback circuitry so they won't verify all the time. Get the errata for your device from Xilinx website and see if this is the case and if it applies to your device (you may have to compare some information on the chip like mask ID). 3) Try the ID Code looping by right-clicking on the device in Impact. Make the number huge and let it run for a few minutes. That will give you a good idea if its a signal integrity issue as well. If it fails you have one. If it passes you may or may not since the data pattern isn't always the worst case.

If you do have a signal integrity issue then its a problem on the board and there won't be much you can do other than mod'ing the board yourself and adding buffers. I'd speak with the manufacturer before doing that. In fact, they should have a good idea if they have an issue since they would have heard from other customers if they did.

Those are some basic things to try. The JTAG bus is pretty robust and reliable in general but I've had problems with each of these issues at different points in time.

James.