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Altera_Forum
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13 years ago

MAX V "Jtag chain problem detected"

Hello I build a testing device - another one (first works fine). One of the testing steps is programming CPLD Max V 5m80z. All signals have been connected but I have a problem. I tested connect...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Did you find out what is causing this? I've been having similar JTAG related issues except I have 2 devices in my chain: Stratix IV GX and Max V. In the JTAG Chain Debugger, both devices show up normally most of the time, but, I get the message "Warning: Uncertain JTAG chain". Occasionally it will show an extra device in the chain as you describe. I don't see this on another module that is identical.

Since it was showing an extra device, I had assumed this was something on the clock line with extra clocks being detected somewhere so I started poking around. When I attached the scope probe (3.9pF / 10Mohm) on TCK it works consistently with no errors. The TCK signal looks very clean throughout the chain. All of the other JTAG signals are very clean as well. Anyone have any ideas? Are there any known issues with JTAG on either of these parts (MaxV/StratixIV)?