Hi, Ply rat

PULSIN has a time-limit ... ( see DEFINE PULSIN_MAX ) and returns 0 if this time limit is reached.

So, you must stay within those limits ... (default 65535 counts = 0.65535 sec @ 4 Mhz)

Take care : that applies to the High OR Low state of your pulse !!!

What pulse length ( or signal ) do you want to catch ???

Could you explain a bit more what you want to build as a device ???

Alain