I think you are right about the MCLR as a CMOS input. I'm surprise about no= t needing to deal with all the other unused inputs if I pull down MCLR.=20 ----- Original Message -----=20 From: "Bob Blick" =20 To: "Microcontroller discussion list - Public." =20 Sent: Wednesday, December 22, 2010 3:24:33 PM=20 Subject: Re: [PIC] low sleep mode current on PIC16F688=20 On Wed, 22 Dec 2010 20:13:15 +0000 (UTC), zipwize said:=20 > The MCLR pull down was a dramatic solution=20 > that I happened upon. I still wonder why.=20 Because it's not MCLR! You configured it to be an I/O pin. And it has no=20 output drivers or internal pullup, so it floats. And floating input=20 circuitry draws power because CMOS logic draws power when the inputs are=20 not at one rail or the other.=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 >=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 --=20 http://www.fastmail.fm - Access your email from home and the web=20 --=20 http://www.piclist.com PIC/SX FAQ & list archive=20 View/change your membership options at=20 http://mailman.mit.edu/mailman/listinfo/piclist=20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .