When I was testing this, I found that leaving the MCLR open caused the curr=
ent to float all over the range. I tried making all the unused pins outputs=
.. I was at my end of patience when I discovered that pulling MCLR down made=
 the current low (70nA) and really stable. I saw the paragraph about sleep =
mode and unused inputs. I tried pulling all unused pins low. Then I tried p=
ulling them up with 15K (using a resistor network). Neither of these made m=
uch difference. The MCLR pull down was a dramatic solution that I happened =
upon. I still wonder why.=20

----- Original Message -----=20
From: "Bob Blick" <bobblick@ftml.net>=20
To: "Microcontroller discussion list - Public." <piclist@mit.edu>=20
Sent: Wednesday, December 22, 2010 2:59:56 PM=20
Subject: Re: [PIC] low sleep mode current on PIC16F688=20


On Wed, 22 Dec 2010 17:55:30 +0000 (UTC), zipwize said:=20

> If MCLR is internal, why do I have to tie it low to get low sleep=20
> current? Is there a better way?=20

"A weak pull-up is=20
automatically enabled for RA3 when configured as=20
MCLR and disabled when RA3 is an I/O. There is no=20
software control of the MCLR pull-up."=20

So if it was MCLR you could leave it floating, but since you have it=20
configured as I/O(actually it can only be configured as input or MCLR,=20
not an output), it has no pullup and you need to deal with it=20
externally.=20

Bob=20

--=20
http://www.fastmail.fm - Same, same, but different...=20

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