Hi,
for my Spartan3, being the internal pull-ups only good for non connected pins, which external pull-ups should I place on my output pins (that go into output buffer, opto and bjt before reaching the output pin of the board), 10kOhm, 4.7kOhm?
Thanks, Marco
Who told you that the internal pullups are only good for unconnected pins?
Are you using these outputs as open collector? If they are driving a BJT, why do you need a pullup at all? Just drive through a series resistor to limit the current. Or you can remove the BJT and drive the opto directly. Spartan3 will drive up to 24 ma, no?
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