internal circuitry matters

[Disha Karnataki]

hi everyone,
i am newbie to micro-controllers.
i read that we write "logical 1" if we want a pin of the port to act as output & "logical 0" if v want to it to act as input port.
i would just like to want to know the internal circuitry the way it is built in to work so.
what is the internal circuit how does uc(8051) will be able to recognize as input or output.
please give detailed information & the internal working inside the microcontroller for seperate cases(i.e input or output)

 

[jrwebsterco]

You should start with a search for "bidirectional port".
For example, take a look at this: **broken link removed**

However, note that many manufacturers sell an 8051 equivalent, and each one might have slightly different implementation, but all should still function the same.

 

[ark5230]

All the port pins are pulled HIGH using pull-ups.
If the pin goes low it can be detected, else it continues to show High !!
This is the simple logic.
By default all pins are high at the power on reset.