Xiaofan Chen wrote 2011-10-10 10:12:
> On Mon, Oct 10, 2011 at 4:00 PM, IB Peter Feucht<feuchts@kabelbw.de>  wro=
te:
>> Now the 684 has an brown out reset, which is pricipally doing what I wan=
t,
>> but I see no possibility to distict between a "cold boot reset" (made wh=
en
>> e.g. batteries are changed) and brown out reset.
>> In case of a cold boot reset the devide should work normally, but when a
>> brownout occured, I'd like to simply disable any further operation until=
 new
>> batteries are inserted.
>>
>> Does anybody have an idea, know of any sort of "hidden features", any so=
rt
>> of dirty tricks to make this?
>>
>
> http://ww1.microchip.com/downloads/en/DeviceDoc/41202F-print.pdf
> Section 12.3.7, Power Control (PCON) Register
>
> The Power Control register PCON (address 8Eh) has
> two Status bits to indicate what type of Reset occurred last.
>
> Bit 0 is BOR (Brown-out). BOR is unknown on
> Power-on Reset. It must then be set by the user and
> checked on subsequent Resets to see if BOR =3D 0,
> indicating that a Brown-out has occurred. The BOR
> Status bit is a =93don=92t care=94 and is not necessarily
> predictable if the brown-out circuit is disabled
> (BOREN<1:0>  =3D 00 in the Configuration Word
> register).
>
> Bit 1 is POR (Power-on Reset). It is a =910=92 on Power-on
> Reset and unaffected otherwise. The user must write a
> =911=92 to this bit following a Power-on Reset. On a subsequent
> Reset, if POR is =910=92, it will indicate that a
> Power-on Reset has occurred (i.e., VDD may have
> gone too low).
>

Problem is, that if the PIC had e BOR due to "low batt", wount
the BOR logic hold the PIC in reset until the you have a
"non-low batt" condition ? That is, forever or until the
batt is replaced ?

I think that BOR will not work to monitor the batt voltage.



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