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Altera_Forum
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15 years ago

Can't scan JTAG chain

Hi all, I had posted this issue previously, but nobody replied. I even created a webcase, but I am not getting any response from Altera. Anyway, I am trying my luck again. I have a Nios dev k...
Altera_Forum's avatar
Altera_Forum
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15 years ago

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but it seems to me that the jtag slave will stay idle if tms stays at 0.

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Absolutely correct. Before a JTAG instruction can be shifted into the device, TMS and TCK are setting the TAP controller to an active state. TMS states of '0' and '1' will be observed during the first clocks. Otherwise a hardware defect of the USB Blaster or your FPGA board must be expected. The TMS pin is used to drive NCONFIG in AS mode, so AS configuration would be still possible.