What do you mean "get data from external interrupts" ?? Interrupts can only notify the microcontroller of events, they can't really be used to give you data, unless you are talking of Serial communication, in which case the interrupt notifies the microcontroller that data is available.

The basic working of interrupts is thus: Each interrupt is associated with a unique vector address in the code memory. When the interrupt occurs on a certain pin, it pushes the current 16-bit program counter onto the 8-bit stack (lo-byte first I think) and replaces it with the interrupt vector address corresponding to the interrupt. It is sort of an implicit function call. So the micro starts executing from this new address, where you code how to handle this event and then return to your main program.

Read the tutorials on this forum to get a good idea of the issues involved in interrupts.

kundi