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Altera_Forum
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17 years ago

Cyclone III user I/O stay LOW during JTAG configration

Hi,all I found all user I/Os became LOW during JTAG configruation in my situation. The device is Cyclone III 3C35. However, it is said that user I/Os must be tri-stated during JTAG configuration i...
Altera_Forum's avatar
Altera_Forum
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17 years ago

I don't know the reason for the specific behaviour. However, dual purpose pins must be expected to take arbitrary levels in configuration state respectively feed a signal. Thus they shouldn't be connected to hardware, that may show unintended reaction. If your design is using AS configuration, the problem arises during POR initial configuration anyway.