> > > The 16F84A is rated for use between 2.0 and 5.5V
> >
> > my datasheet says the '84 is good to Vss+7.5V max rating.
>
>     Your datasheet says that the "Absolute Maximum Rating" is 7.5V.
>
>     Absolute Maximum is the point beyond which permanent damage to
>     the device can result.  Operation at Absolute Maximum is not
>     guaranteed, and extended exposure to Absolute Maximum conditions
>     may hurt the device even if the Absolute Maximum isn't exceeded.
>
> > I regularly run '84s with 6V batteries.
>
>     Then you're running them out of spec.  The maximum operational
>     voltage for the 16F84A is 5.5V.
Also, SOME versions of the 16F84 will run at 2V (maybe) with SOME clock
configurations. AFAIK without going back yet again and looking at the data
sheets, bog standard 16F84s are not specced to run at 2V.

That said, I have a small batch of devices which use a 3.6V NiCd battery
pack and run at about 250 KHz. I use standard 16F84's and they work fine
there FOR ME in this application including EEROM writes and reads. YMMV.


regards

            Russell McMahon

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