Jan-Erik Soderholm wrote:
> On 2010-11-28 23:59, David Duffy (AVD) wrote:
>  =20
>> Olin Lathrop wrote:
>>    =20
>>> David Duffy (AVD) wrote:
>>>
>>>      =20
>>>> I am using INDF0 for reading the receive buffer.  It is the same code
>>>> I've used countless times before.
>>>>
>>>>        =20
>>> Are you doing this in the interrupt routine and forgot to save/restore =
the
>>> FSR?
>>>      =20
>> I am using INDF0 in the serial receive ISR, as well as in tasks
>> triggered by flags in the main loop.
>>
>> I'm not saving / restoring them in the ISR, as I understand this
>> particular chip does that by itself.
>> David...
>>
>>    =20
>
> They are. But of course you have to re-init them at each
> entry to the ISR, they are not preserved between two interrupts.
> You didn't say you don't, but just to clearify.
>
> B.t.w, this is what the PIC16F193X/LF193X datasheet says :
>
> Upon entering an interrupt, the return PC address is
> saved on the stack. Additionally, the following registers
> are automatically saved in the shadow registers:
> =95 W register
> =95 STATUS register (except for TO and PD)
> =95 BSR register
> =95 FSR registers
> =95 PCLATH register
> Upon exit from the Interrupt Service Routine, these registers
> are automatically restored. Any modifications to
> these registers during the ISR will be lost. Depending
> on the user=92s application, other registers may also need
> to be saved.
>
>
> What I do not understand is why you don't read the receive
> buffer (RCREG) directly. Why go through the index registers ?
> The reading will always be from the same fixed address (RCREG)
> so I do not see the need for any "indexing" here !?
>  =20

To clarify, I use INDF0 to store the incoming byte into my RAM receive
buffer.

Also, the use of INDF0 in the ISR & main routines is separate. That is,
they operate on the same buffer, but the pointers are separate variables.
David...

--=20
___________________________________________
David Duffy        Audio Visual Devices P/L
Unit 8, 10 Hook St, Capalaba 4157 Australia
Ph: +61 7 38235717      Fax: +61 7 38234717
Our Web Site: www.audiovisualdevices.com.au
___________________________________________

--=20
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