Hello Raghunathan R,

Why do you want to reinvent the wheel when there are 10,000 sets laying all around you?

How about taking an IBM keyboard, a PIC 16F84 with the software already written, which will output the ASCII key out using serial format. Then you can read the information using the serial port of the 8051.

You expand from 40 keys to 104. The unit is all packaged and is super cheap to buy.

Just a suggestion.

Regards,

Charles Bannister