> > Questions:
> > 1) should I disable GIE in ISR or leave it on?
>
> Depends on what you need to happen.
>
> > 2) if I leave it on, if an interrupt occurs during ISR, it will call
> > ISR again from start ?
>
> Yes

There seems to be some general confusion here.  First, GIE is automatically
disabled when the interrupt is taken, so you can't "leave it on".  GIE will
be re-enabled by RETFIE at the end of the interrupt.

You do **NOT** want GIE on in the interrupt routine.  This can cause an
interrupt within an interrupt.  You would have to go thru a lot of trouble
to make sure your interrupt routine is re-entrant to handle this case.
Think of what your interrupt routine will do to the saved state of the first
interrupt if a second one comes along before the first completes.  In theory
you could make your interrupt routine re-entrant, but I think this is
extremely unlikely to be a benefit in practise.  Also note that extra call
stack locations are used up globally if you allow nested interrupts.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, STOPspamolinembedinc.com, http://www.embedinc.com

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