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> Difference Between 89c51 And 89s51?, Sinking and sourcing ports
Qaisar Azeemi
Posted: December 24, 2011 06:15 am
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Can any one please explain the difference between 89c51 and 89s51? and what is the sinking and sourcing ports of microcontrollers.. i mean to ask what kind of microcontrollers have sinking ports and what kind of microcontrollers have sourcing ports?
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sherlock ohms
Posted: December 24, 2011 11:25 am
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no help here, but it is an interesting question. seems to me it shouldn't make a difference where the switching takes place..no doubt (as always) there's more to it.. i'll be staying tuned on this..

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Posted: December 24, 2011 08:09 pm
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Not having used 89C51s and similar, all the uCs I've used have configurable four state outputs: open, weak pull up, active high or active low. No sinking (open drain) outputs. You can simulate open drain behavior by toggling the drive state (active or passive) while assigning a low output state, so it switches between open circuit or active low.


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Posted: December 25, 2011 10:38 am
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PORTA on old 8051s was open collector no? or just during programming - i forget.

Anyway, 89S51 I've used this lifetime, and it has quasi-bidir outputs.. ie 1 is weak pullup / input, 0 is open collector pullin down.

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