Erik,

Most of the applications that I have worked on have communications going on and user input at the same time, so I can't risk losing a character coming in from the communication port, therefore interrupts are disabled during the communication ISR. I also keep my ISR's short so that I can catch any other interrupts that happen. On each interrupt the PSW, the accumulator and any other registers that I am working on are pushed onto the stack. This can add up if the nesting of ISR becomes great. I guess if the interrupts are few, then there is no problem. But in most of my applications, the communications port really gets used often.

Regards,

Jacob