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Altera_Forum
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14 years ago

Weak pull-up resistors

Hi everyone! I enabled weak pull-ups for the input and output pin (cyclone II device). But when I measure the voltage on these pins, on the input pin is 3V and on the output pin is 0V. Shouldn...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

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After compiling the project, there is one warning about the output pin that says: "Output pin is stuck at GND".

--- Quote End ---

Then it sounds like you have an output defined, but you have left it undriven, so Quartus has provided a default for you.

Try this instead:

unused_output <= 'Z';

Quartus will then warn you that it has used a permanently disabled tri-state. However, this will force your output to be tri-stated, and your weak pull-up will pull it high.

Cheers,

Dave