Thanks for the tips

What I did was use the whole 80 locations of BANK2 to act as a buffer.
I needed a complete sentence before I could process the data.  Using
this technique works well, but seems to waste a lot of memory
locations.  A flag is then set once the buffer wither fills up or the
end character is read and then a routine in the main loop does all the
processing as slowly, and throwing away of junk, as slowly as it wants.

BTW it was NMEA from a GPS, and some of the sentences it sends are
quite long.

Cheers for the help.

Ed

On 25 Mar 2004, at 19:06, Jan-Erik Soderholm wrote:

> Edward Cooper wrote :
>
>> I have some code which handles...
>
> Could you define "handles" ?
>
>> ...a string from the serial port in the ISR (using USART receive
>> interrupt), effectively hanging the processor for a short time.
>
> Define "short time" !
>
>> During this period I will have multiple TMR0's occurring
>> of with I can't miss one because its using them to rack up a timer (in
>> milliseconds) for a time critical process.
>
> Aha ! So "short" above is > 1ms, right ? But 1ms whould be plenty
> of time to save the character from the USART.
>
>> Now I'm not entirely clear if another interrupt can occur while one is
>> in process?
>> I'm thinking it can't because it would just mess up the
>> PUSH and POP process, or would it!?
>
> The specific interrupt *flag* can be set, but the interrupt jump
> will not occure before you leave the current ISR.
>
>> Basically the TMR0 process is very short,
>
> And the you must make the USART ISR shorter then the intervall
> between two TMR0 interrupts. This should be no probalem at all.
> You have plenty of instructions in 1 ms  to save in incomming
> character !
>
>> I just need it to occur while the processor is still dealing...
>
> Define "dealing" !
>
>> with the serial receive.
>>
>> I think I should really look into handling this serial receive outside
>> of the interrupt?
>
> You should/could save the incomming character in an UART ISR, but
> do whatever has to be done about it, in the main loop. Just set a flag
> in the UART ISR saying "there is a new character received !", and let
> the main loop check this flag.
>
> Jan-Erik.
>
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