There is a difference between a 1 --> 0 transition and 1 --> 0 level change for the external interrupts. This is cuationable.

If you have fixed external interrupt type to be transitory then after the ISR has been served it will not activate again untill another transition occurs, not matter the port is still at 0 level.

However, if the interrupt you have set as level type, then after the ISR the interrupt will keep on occuring as long as the port is at 0 level.

See the data sheet you will know how to set the interrupt type.


One thing is to kept in mind that transition speed must be far less than the interrupt polling speed. Otherwise I think if transition is too fast then your desired interrupt may miss.

Before you do anything try reading stuff on interrupts on your left side in the tutorial. Its worth it.

Steve, Box ??

Babar/