Thank you Wagner, and thanks again..  '

That works for me. The zeroth element of the RAM is corrupted on restart as
you predicted, but that is OK as I can just use this as a part of the
volatile RAM which I must have anyway, you PIC boys sure do have the
answers!

The backup current is now down to the more reasonable uA level so this is a
100% fix for me.Great :-))

Thanks again.... Barry


----- Original Message -----
From: Wagner Lipnharski <wagnerl@EARTHLINK.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, August 30, 1999 7:21 PM
Subject: Re: Static RAM memory retention Circuit


> ooops, wrong circuit at the previous post... I am getting old and dumb,
> this one here doesn't need even the resistor to keep PIC +V polarized
> and hold /CE /OC and /W at up level while switched off. The Ram chip
> will be at 0.7V above ground when PIC is energized, I can't see any
> problems, do you?
>
> +5VCC--------o---------------o--------------.
>              |               |              |
>              |               |              +
>             PIC             RAM             3V
>              |               |            Backup
>              |               |            Battery
>     Switch   |               |              |
>         /    |    diode 1    |    diode 2   |
> Gnd---o/ o---o------|<-------o------>|------'
>