Hi Waqar,

Your two questions are basically the same, with two entirely unrelated points...starting execution given an input, and how to use a port pin.

Have you *still* not read the 8051 bible mentioned so often here?? It gives a clear description of how 8051 ports work--and the differences between port PINS and port LATCHES. You NEED to understand this. Many people here have clearly told you how you need to change some of the code you've listed previously to enable you to use a pin as an input, and why you need to do this. Perhaps once you understand HOW the port works, you'll agree WHY you need to change your code.

I suppose if you really wanted to START execution of code when an external signal goes high, you could invert the signal and connect it to RST. When this control signal goes high, the uC's reset goes away and it can start up.

Or you could invert it and connect it to one of those INTx/ pins, and have your interrupt service routine set a flag that indicates to the main loop to start doing something.

Dennis