San it is two questions,

I still dont see any way to expess a vector with the instruction set. Might take a fresh look. Starting to get a little less hazzy.

With the flags, how else would program flow be deflected? With CJNE,
one of carry flags might be looked at. I would think that interupts would be trigered in a simular way.

But its a bit mysterous. Why would the 8052 be constantly looking at the flags, to triger interupts?