period measurement

Hi, I am marlon and I would like to ask about period measurement. I have a external frequency that goes to PE0 of rab3000 and I would like to measure the period accuracy of it in micro seconds. The frequency is 14hz, 16hz, 1 hz and 0.5 hz. the duty cycle is 50% and its is a square wave up to 3 volts in amplitude.

thanks