I am triyng to make an interrupt routine to control the entrance and exit of a client from a taxi car.The problem is that I dont know exacly what I should choose: Level triggered or edge triggered. I must detect if the taximeter is ON or OFF.When the taximeter goes OFF or ON an interrupt is triggered and some variables will be updated. Can somene help on that.Does anyone have exaplme of interrupt routines for the P3.3 or P3.2? I am using the P89C51RD from Philips.