Rabbit rcm 6700 serial interrupt

I’m having trouble setting up my serial interrupt with my rcm6700
I have the external interrupts working great, but getting the interrupt to happen in response to serial input is questionable.
I have something happening (with my interrupt “set up” I no longer get a working serial in from the serial port (F))
however, I have put a print statement in my interrupt and it does not print

SetVectExtern(2, serialF_isr);
// WrPortI(I2CR, &I2CRShadow, 0x01); // Enable serf INT, priority 1

root interrupt void serialF_isr()
serEputs(" o ");
ser_F = 1;

I never end up with " o " showing up in hyperterminal??


ISRs are supposed to be short and in assembly language if possible.

Instead of having the serEputs() function inside the ISR, set a flag, get out, and in the main loop of your code run the function if the flag is set.