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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

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

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This information is inconsistent. If an ohm-meter indicates 0-Ohms between the core voltage and ground, then its a short, and you would not see a voltage when you turn the supply on. (You be making the impedance measurement with the power off).

The I/O impedance can sometimes be close to 0-ohms if you have a lot of bus terminations, but for this test, you just want to look at the core.

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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...

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That definitely sounds like an issue. The Terasic USB-Blasters are cheaper than the Altera ones, and I've never had a problem with them.

Cheers,

Dave