8051 CPU IO Pins

Maurice Reid heeft geschreven in bericht <37450FD6.5BA0@tesco.net> RE: the datasheet specs for the 8052 pull-ups. I'm trying to drive a ULN2003 darlingron array using these ports but haven't worked out if it is possible. The port drivers are specified in terms of Iil at 0v (about -50uA). Other parts talk of the pull-up being equivalent to a 10K resistor. But the figures don't seem to add up

Maurice, If the voltage on the pin is below threshold (as with the darlingtons) a weak pullup is present. If above threshold the internal resistance is 10x lower. Use real pullups on the outside. Arie de Muynck

.8051 I/O usually outputs logic high during reset which can be a pain, as well as having weak pull ups all the time, and this can mean more external hardware considerations.

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