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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

If that is true, you might have to use external pullups.

The fpga's internal pullups can't possibly be asserted until after the fpga itself is configured - which will be well after power is applied. I guess the pins are hi-Z until then.

If the peripheral has a separate power supply, then the pulling the signals high from anywhere else will lead to the device being back-powered from its inputs.