The chip I'm using is the ADuC812 microconverter.
I have now decided to write an interrupt service routine.
Basically what I want to do is when the square wave comes i on P3.4
I 'll start two timers and when the wave comes in on P3.5
I'll use an interrupt service routine to stop the timer1, store the value. When the first square wave has gone through one period I'll write another service routine to stop timer0 and store the value in timer0 and then start timer0 and timer1 again immediately.