simple example code to use serial interrupts for the PIC16F877.
1) a matlab program sends the PIC numbers
2) the PIC will pause whatever it's doing,
3) get the numbers and display them on LEDs,
4) and then continue on with what it was doing.
see the code in the txt file. It is very simple and very well commented and it's a bare minimum of what you need for PIC serial interrupts. The txt file has the matlab and the PICBasic code. Took me a day to figure all this out and boil it down to the essentials (what you'll find in my txt file). The PICBasic code is based off of example code from the internet.