Mr. Rob Redding wrote:
(http://www.8052.com/forum/rea...0294&top=)
A simple way ,if you have a spare pin is a RC circuit..

connect a resistor in parallel with a diode (cathode to VCC) to VCC.
then connect a capacitor to the diode anode and to ground.then connect
the diode anode to the port pin through a 1k resistor.

when you first powerup the circuit , the capacitor will not be charged and
you will read 0...after a time the cap charges giving you a 1.

the diode and the 1k res protect the uC when you turn off the power.
=========================================================== 
<p>Mr. Rob Redding wrote:
(http://www.8052.com/forum/rea...&top=) It is really ,but
describing it is the hard part... I wish I could draw.... ============================================================== </p>
<p>

Mr. Michael Karas responded with:
(http://www.8052.com/forum/rea...&top=)

==============================================================

My Response (Dollar short and Day late)

THIS IS A SUPER 8051 FORUM. </p>
<p>Regards, </p>
<p>
Charles Bannister</p>