How can i count the no. of pulses that comes into pin of microcontroller 89s52?

Muhammed Shafi a écrit :

Sorry, I'm not sure to understaind.

A person starts blowing. Second 0 to 1 : You count the rotation of fan (for 1 second) Second 1 to 5 : You do nothing Second 5 to 6 : You count the rotation of fan (for 1 second)

It's that you want ?

Warning: I'm a software developer who dabbles in microcontrollers as a hobby, not a pro as far as microcontrollers are concerned.

What you could do (if your hardware supports it) is set up an interrupt that gets triggered by signal level or status change on your pulse input. In that interrupt, increment the n-th location of an array of ints. Increment the index n every second (starting with n=0), using e.g. your timer.

That's the basic idea - you'll have to make sure your counting is correct, you initialize your array with all zeroes before counting, your integer type can handle the maximum number of pulses per second, your array is large enough to handle the maximum expected expiration time (and you do something sensible if that is the case nevertheless) but basically, you'd end up with

int pulses[MAX_SECONDS];

where

pulses[0] is the number of pulses in the first second, pulses[1] is the number of pulses in the second second, ... pulses[n] is the number of pulses in the last second

You could stop measuring once there's a couple seconds with 0 pulses. (If that is your problem - you really need to explain more about what you intend to measure exactly)

Regards, Gilles.