A. Post

I must eat my version of the 8051 interrupt control logic. I did some reading, and The 8051 doesn't "remember" what status it's in, it establishes interrupt status every 5th t-state by polling all involved (and software accessible, as you said) bits and by looking at the instruction being executed. It can be fully manipulated by software.
I wouldn't recommend it though, it's not a clean technique.

Al Gore