Sourcing and sinking currents for AT89S51

[sam288]

This may seem like a really stupid question..but how do we know what is the maximum current a micro controller can source or sink for logic 0 and 1....there are various currents given in the datasheet.. but i dont know which ones to read...
Can anybody tell me the values for AT89S51..

 

[Wond3rboy]

Page 20 of the attached datasheet has the current ratings with respect to port pins as well as ports.

Sink current is Iol i-e current o/p low.

Source:Maximum DC o/p current is listed on the same page.

 

[be80be]

It there but this is it in a nutshell

Port 0: 26 mA Ports 1, 2, 3: 15 mA
Maximum total IOL for all output pins: 71 mA