Hi Louis,

Try using something like this :

set up a timer (1mS?);
every tick, compare P0 with previous value (XOR);
if no change, quit routine;
loop for all bits of P0 :
if P0.X changed & is now active (low?), incr sensorX;

If you're counting cars, you should have enough cpu time left for other stuff.

Regards,

Richard