V.DURGAI DASS wrote:
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In other words, to make a port as input , you have to write a 0x01 to that port pin before reading that port pin as input.
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Now, this confuses me too much. Can you please explain the I/O functionality of 8051 with respect to 8255. ( I understand that at any given moment 8255's ports can either be used for Input or Output but not for both and this is defined by the Control Word. As opposed to this, 8051 ports can be simultaneously used for Input as well as Output. Now, is there any special instruction or value that I should pass to those ports ...MOV Px,#xx, to get what I want)...
Im reading the pages erik suggested (its a very big file and is taking hell lot of time for me to download. I'll get back after I finish reading it.

Warm Regards,
Sriharsha