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Altera_Forum's avatar
Altera_Forum
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16 years ago

Jtag Problem

Hello everybody, i have big problem, i use CIII FPGA on my own board (EP3C16Q240). I try use USB BLASTER (Rev. B), but this is response: Error: Can't access JTAG chain Error: Operation f...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

1 - I would of course check with another USB blaster just to make sure your Blaster doesn't have some issue.

2 - If you have an oscilloscope at your disposal you should take a look at the JTAG signals on the board just so you can understand what's going on.

3 - If the USB-Blaster is working properly my first suspicion is that you are right on a timing edge that the USB-Blaster is unable to resolve. Here are some things you could try:

a - Try adding some capacitance to the JTAG traces while you try to scan the chain. Like holding a screwdriver tip on the clock line or data line. Sometimes this added drag on the signal can be enough to push things into a working condition.

b - Add a small series resistor into the TDO trace, TCK trace, or TDI trace.

c - Try adding a bit of cable between the USB Blaster and the JTAG header on your board.

Can you describe your JTAG topology?

Jake