Michael Karas:
This problem is very easily solved by making a state machine for each function. The realistic timer interrupt interval for this process is more likely to be 5 milliseconds. 1 microsecond is rediculous - that is less than one machine cycle on a standard 8052 with 11.0952 MHz oscillator. At 5 milliseconds you can setup the timer interrupt to call the state machine modules for each of the four inputs at each timer interrupt.

Waquar:
can you please suggest any book for state machine coding type..

Terry Lingle
waqar At the top of the page is a search engine - enter "state machine" and read the 161 results. Again you ask others to spoon feed you

Waquar:
Please check this code which has nothing to do with a state machine

In other words, Michael tells you how to do it, Terry show you where to find the information and you throw some half-baked code at us. If you had followed Michaels suggestion, used Terrys guidance, you would have been helped along and your question here would have been valid

Erik