Hi Henrik,

Thanks for the reply - I knew I could count on you for some helpful advice.

I understand the concept you've mentioned and have this working with good results - if I state 100% DC is 1000us. I'm using a 12F683 with 2 pots to emulate the engine, one for variable frequency (5-55hz = 600-6600rpm) the other for variable pulse width (0-1000us) and a switch for pulse polarity choice. Resolution needs to be 10us (equivalent to 1% DC).

How do I track the overflows? I've not delved into timers before this.

Thanks for your help as always,
Bill