Hi Trevor
There are some processors designed to accept high voltages but generally this is very dubious practice and it is best to keep clear of such short cuts.
Use for example an optocoupler (most have 2000...4000V isolation) and keep everything well safe.
If you want to count cycles then the output of a unidirectional optocoupler can be connected directly to a port (or better timer) input with a pull-up to the supply voltage you are using.
Note also that the ADC in the MCF5213 has a zero crossing interrupt function. Although maybe not relevant to your application, it can be programmed to automatically monitor analog input signals and trigger when a signal crosses a 'zero' threshold in either or both 'directions'. The interrupt does however have to be serviced since each time the detection occurs - it needs to be reset to enable the next trigger, but it could be used as an AC line zero detection using a suitable isolation transformer....
Regards
Mark Butcher
www.mjbc.ch