Hi,
For multiple interrupts (2 or more) that are active LOW, the following circuit should work:
The pullup resistor keeps the INT / in0 input high as long as none of the inputs gets low. Use schottky diodes for a sufficiently low voltage drop across them (I always use BAT85).
Note that due to the orientation of the diodes the inputs are always isolated from each other, so you can connect any output combination to them without any problems. Of course the LOW interrupt signal should be available on the pins long enough to allow detection in the interrupt routine by reading the state of the input pins in order to decide which input actually caused the interrupt.
In case of an active HIGH interrupt, reverse the diodes and have a pull down resistor to GND instead.
Otf course SETINT should be used to properly select the interrupt input port.
Best regards,
Jurjen
www.kranenborg.org/ee/picaxe