The interrupt vector location whould only EVER VECTOR to the Interrupt service routine. Don't put code in there if you can help it.

Interrupts are usually triggered by the setting of a hardware flag in the system that the interrupt generating mechanism scans regularly. The original Intel family notes (wherever they have gone this time) take a great deal of trouble to explain just where in the machine cycle of the old 12 internal cycle instruction processing system the interrupts are sampled.

Many of these flags reset themselves as the interrupt is called, and you don't have to do the housekeeping. On many extra facilities in variants like the one Jeff is using, the newer facilities have flags that you have to reset yourself. Or Else.

Unused interrupt vectors should ideally contain RETI statements BTW, then an out of control process doesn't wreak as much havoc as it could do.

Steve