Question: Receiving double interrupts from serial port routines even though I am clearing them at the end of my Interrupt Service Routine (ISR).

Answer: To ensure that you do not receive a double interrupt, you should clear the Interrupt Flag Register (IFR) bit (XINT or RINT) in the corresponding interrupt service routine (ISR) just before returning from the routine. See the Note: on page 9-6 in the C2xx User's Guide (1997 SPRU127B). There is an example of how to do this in Example C-13 on page C-20 in the 1997 C2xx User's Guide. Note that to clear an interrupt, you write a 1 to the corresponding bit in the IFR as explained on page 5-20 to 5-21 of the 1997 C2xx User's Guide. Needs to write a 1 to that bit to clear that flag- then follow the example on page C-20 in the 1997 C2xx UG.