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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

Initially (before configuration), all FPGA pins are driven high (at least near to Vccio when considering leakage currents). When you say, they are not high initially, the pins are either pulled low externally, or you pull them low after configuration, which just means an unsuitable way to drive the pins in your code.

The only cases, where an external pull-up would be required is to override other external loads or for clock inputs, that don't have a pull-up.