Hi Allan,

it seems, you have not read my example:

http://www.specs.de/~danni/training/reti.a51

I agree, that I need never to do such in my practice. So I wrote it only for education purposes to tell, how the 8051 interrupt logic work.

To my example:

It works fine, since all critical actions done by disabling the interrupt (setting the in progres flag and push all needed registers).
There is also no danger to push additional registers in the low level interrupt, since the high level interupt use the same routine to clear the in progress flag and pop all registers. Since this also was done with all interrupts disabled again, also additional interrupts are safe.
Only subroutines can not be called in the low level interrupt or must complete be done with interrupts disabled.

Please simulate my example to understand the working.


Hi Simon,

to write code only for education purposes seems also a reasonable intention. Also to do academical talk.


Peter