> Actually, I'm still trying to figure out how to multiply a clock pulse. > If I take my clock pulse, xor it with it's 90 degree retartded friend, I > would double my original clock. Usual technique to double frequency of a digital signal is to xor it with a slightly delayed (delay << signal period) version of itself. This gives you a short pulse (of width "delay") at each EDGE of the original signal. If your square wave is of reasonably low frequencies, and is known to change frequency at a relatively slow rate, I would be tempted to use SOFTWARE in a PIC or something to delay each edge by half the period of the previous pulse. This would give you "almost" a 90 degree (does that mean anything for a digital signal?) phase shift: _____ _____ _____ ___/ \_____/ \_____/ \_____ Input 10 10 9 9 8 8 | __________ ______ _____ XX \_____/ \_____/ \_____ Output | 5| | 5| |4.5| BillW