Dennis - I'm going to have to hang onto your e-mail address - you might
save my arse on a few occassions as I move forward with this little design
- haha.  Thanks very much again for the tips.  Looks like I might be ok on
this one - The micro I probably will use will be the '620 in most cases and
it's spec'd down to 3 volts - no biggy problems here - by the time the user
will be inserting the second battery , the little bugger will have powered
up, initialized and then gone to sleep again - when the second battery
comes "on-line" and the Vdd jumps to 6V - nothing will (should) happen -
the only way to get the micro up and going is to press the button on the
front panel.

I noticed that the F84 does go down to 2 volts in one version but can't get
it to run at 4MHz there - only 2MHz.

These PICs look great!  It's midnight here and as usual I'm too keen
(foolish) to go home ....  If only I had a programmer now - I have been
fiddling with the simulator for the last week on and off and have most of
the code "running" as best I can tell.  I'll have to spring for that
Picstart plus tomorrow and order it in I guess.  BTW - is there a "dirt"
simple programmer design and piece of code i can get on the web to program
a test program into the F84s I have in the meantime?  I'd like to at least
put the processor to sleep and watch a led blink when I press a push button
hooked to port B...

I should stop tormenting you and let you get to work - and I should bail
for home for the day :)

Cheers and thanks a million again...

Lewis



>OK all seems good! Normaly there is no problem when running on batteries, as
>the battery can be considered "Brown out free". During insertion the rise
>time for VDD is fast, however if it is below the minimum level (4V) then the
>chip will not exit reset correctly (OSC may not startup, thats generaly the
>only thing. In this case putting in the other battery will kick start the
>OSC, note that the on board stuff may not be reset correctly). Now what can
>you do about this?
>
>1/      Nothing, as the thing will go when the new batteries are in (Follow
>the above and all should be OK)
>2/      Enable the watchdog, this will issue resets until the "cows come
>home" if the PIC is not running. This will always draw power and will "Wake
>up" the sleeping processor (Not very nice, but is handy in some projects)
>3/      Use an external reset type chip Seiko make some nice ones here that
>draw nanoamps! At a cost of around 18 cents in quanty.
>
>
>
>Dennis
>
>
>-=====================================================================-
>
>Dennis Plunkett: Embedded Hardware, Software design
>NEC Australia DRMASS
>ph 03 9264-3867
>
>-=====================================================================-
>
>