Dear Rashu,

SO you have already heard from a very senior member on the 8255!! He is very correct in that this particular 82xx series of peripherals from Intel have had thier time and were fine during thier days. They had quite a complex set of control registers - have you tried to read the data sheet of a 8279 keyboard cum display controller ? I have in the past and will not in the future.

I wish I could upload an image here. ( My previous efforst have failed - though the code was correct.) Anyway let me reproduce verbatim the diagram that was sent in by Mr Michael some time ago. ( Can I Mike ? Thanks )

The port pin via a 2.2K resistor connects to the base of a PNP transistor ( any general purpose type like BC557 ). The base is pulled up to Vcc via 10K. the emitter is also connected to Vcc. The collector load is the LED + 270 Ohms resistor to GND.

Have fun without frying 8051s.

Raghu

I am sorry that I am drawing in "text" !