IJAZ:

Your post regarding the configuration of I/O ports is misleading and wrong. Use care about how you explain things.

There is NO truth to your proclamation that If you want to write "1" to a port pin you should first write "0" and then "1"

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The port pins of a generic 8051/8052 are bidirectional. The input side when you read from the port logic will always read the state of the I/O pin, whether it is being driven by the 8051 or by an external driver.
The 8051 output port side of a pin can pull the port pin low when a zero is written to the output latch. When a one is written to the output port latch the driver lets go of the port pin and a weak pullup resistor on the order of 100K ohms pulls the port pin up toward Vcc. In the condition where the output port latch bit is set to a one and the 8051 output driver has let go of the I/O pin then an external driver is free to swing the port pin up and down as it sees fit as an input to the 8051/8052.

I hope this clarifies the situation.
Michael Karas