PIC18F46K22 MCLR internal PU resistor

gjs_rsdi · Joined: 06 Feb 2006 Posts: 468 Location: Bali

Hi

I am using usually 10K resistor on the MCLR and it works fine.
My question is someone using the internal weak PU resistor on the MCLR of the PIC18F46K22 ?

Best wishes
Joe

temtronic · Posted: Thu May 04, 2017 5:43 am

Not me.....didn't even know it did.
I've always used a real 10K pullup. Now I just read about it and it's disabled during a 'power on reset' whether that affects your PIC code / operation...hmmmmmmm.
Frankly I've got 10,000 10K resistors here,so cost isn't an object. It doesn't really take up any board space, so that doesn't matter.
and
if it ain't broke.... it don't need fixing !!

Interesting though..off to build an Ark...ANOTHER 2" of rain today...sigh..

Jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19552

Quite a few later PIC's have this feature.
If there is no significant length of track attached to the pin, and the environment is 'low noise', then it functions adequately. If there is any length of track, or the electrical noise is significant, then an external pullup is recommended.

gjs_rsdi · Joined: 06 Feb 2006 Posts: 468 Location: Bali

Thank you for the answers
The question is how to use it. I suppose Microchip had something in mind when adding the resistor.
MCLR pin not connected maybe?

Best wishes
Joe

Ttelmah · Joined: 11 Mar 2010 Posts: 19552

Exactly.

It's always there if the pin is setup as MCLR, so nothing involved in 'using it'. It ensures that when the pin is set as MCLR, it is never floating.

gjs_rsdi · Joined: 06 Feb 2006 Posts: 468 Location: Bali

Thanks again Ttelmah

Best wishes
Joe