Starfire Zhu wrote:

> My problem is about the identification of RESET STATUS of PICs at work.
> If the PIC(e.g. P16c54) has disabled the WDT and doesn't use SLEEP on
> whole process, after RESET on MCLR, how could I reliably determine
> whether this RESET is caused by POWER-ON or MCLR? In other words,
> is there any FLAG BIT that can change its value in different RESETs?

I get the PICLIST in digest form and I kind of waited to see if anyone
else might answer you but since I can't find a reply, here is my two
pence.

An idea that occurs to me (someone please correct me if I'm wrong) is to
write value(s) from the EPROM into RAM variable(s).  On a MCLR reset, the
values should be unchanged.  On a power-up, the RAM locations come up
with random contents.

Your initialization code can check for the correct values.  If they are
not present then you know that this is a power-up so you write the values
into the RAM locations.  Of course, if they are there, then you know you
are resetting from a /MCLR.

If you use one 8-bit variable, then the chances are 255 to 1 that
power-up would produce the same value; two variables = 65535 to 1, etc.

I have never tried it, but it makes sense.

Michael

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The strong do what they have to do and
the weak accept what they have to accept.
                             --Thucydides