Hi all thanks for reading.

I'm using a Atmel 89C51ID2 (Not sure if it matters for this question)

Is it possible that if when returning from an interrupt while a lower priority interrupt is
being blocked that before the blocked interrupt is called instructions from the main program get executed?

I've been reading through the "bible" and found this...

"In operation, all the interrupt flags are latched into the interrupt
control system during State 5 of every machine cycle. The samples
are polled during the following machine cycle. If the flag for an
enabled interrupt is found to be set (1), the interrupt system
generates an LCALL to the appropriate location in Program Memory,
unless some other condition blocks the interrupt. Several conditions
can block an interrupt, among them that an interrupt of equal or
higher priority level is already in progress."


So if I'm reading that correctly it takes 2 machine cycles plus the cycles that it is blocked
for the interrupt to get called.


"Several conditions can block an interrupt, among them that an interrupt of equal or
higher priority level is already in progress."

So what are the other sources of a block besides another interrupt?
Does the main program continue to execute while the block is on?