Hello Kashyap Deepak,

This project has been done many times. It has been written up in a book. The title of the book is "The 8051 Microcontroller Architecture, Programming and Applications". Author is Kenneth J. Ayala.

He describes the hardware and software on page 158 entitled "Pulse Measurements".

You could do better by using a CD4060 IC in place of the LM555 IC. The CD4060 features a built in RC (resistor Capacitor) oscillator and a bunch of divide by flip flops which means use a higher oscillator for more precision.

Get a hold of the book and you can have your answer in five minutes. ISBN 0-314-72278-2. There was another article featured in Circuit Cellar about 1992 during the same thing.

Regards,

Charles Bannister