Neil Baylis wrote :

> The two interrupts would be:
> 
> 1, an interrupt for receiving a character.
> 2, an overrun interrupt.

What is an "overrun interrupt" ?
I don't think that the overrun condition as such
generates any interrupt. does it ? It just sets the
OERR bit, AFAIK.

Phillip, are you checking/testing the OERR bit ?
If not, can you be sure that what you see realy is
an "overrun" ?

Phillip wrote :

> Yes you are correct I could just run everything at the
> same priority. But I should be able to put either one of
> my serial port ISRs as a high priority.

Yes, if your compiler correctly handles the differences
between high and low prio interrupt. Different save/restore
of context and so on. Sometimes there are limitations
on what you can and what you can't do in an interrupt.
There is also a risk that one by mistake uses the same
temp-varaible in both interrupt levels.

But my point was that for these two interrupt sources
(at the current baud rates) the added complexity of double
interrupt priorities isn't realy needed.


Jan-Erik.



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