Thanks Russell

But the problem is for how long a tick counter can go
Any no. of Karts (up to 12 max)may pass finish line simultaneously.& this will 'on' for whole day

reports required r no. of laps,time for each lap for each user(Kart).

Still I think I should give it a try what u have suggested.
I dont understand how to keep track of every kart, even if I use multiplexed interrupt & check the port pin still I think its tough to maintain time record for evry kart may be taking arround 30 - 45 Sec to complete the lap.
Apart from it I need to resolve interrupt at very same instance to maintain accuracy.


Regards
Kaiwalya