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Altera_Forum's avatar
Altera_Forum
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15 years ago

Is chip fried? Can't access JTAG chain

I'm new to Cyclone IV design... I accidentally applied 3.3V to the core of a Cyclone IV today, so it's very possible that the chip is fried. When I try to configure it, I get the "Can't access JTAG c...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Thanks Dave. That was good info. The supply voltages are good. And the supply rail impedance is practically 0. So maybe the chip's alright

When I step through the JTAG state machine in the debugger, I don't see TCK or TDI change. TDO and TMS do change, but they only fluctuate between ~0.7V and 0.9V. (I'm expecting 2.5V)

So I'm thinking the USB-Blaster that I bought on eBay is the problem. Cheap Chinese knockoff...