Using MCLR pin at Input

[JakeMend]

I am using a 12F683 and having no luck in disabling the MCLR pin (pin 4 bit 3) so that I can use it as an input.

In the PicBasic program, I put ANSEL = 0 to set all the pins to digital and CMCON0 = 7 to turn off the analog comparators.

In the hardware, I attached a 1K ohm pull-up resistor to pin 4, since I read that as an input, the internal pull-up is disabled.

In the meProg, configuration sections, I set Oscillator to INTOSCIO and th MCLR Pin Function to Input Pin

In the meProg, Option section, I checked both Update Configuration from File and Reread File Before Programming.

And yet, the MLCR pin 4 (bit 3) remains a Reset and not an Input.

What am I doing wrong or not doing to disable the MCLR function?

Thanks,

-Jake

p.s. I also tried to program other 12F683 chips just in case the one I was using was bad, but they all worked the same way.

[HenrikOlsson]

Hi,
To me it looks like you're doing everything right though neither ANSEL nor CMCON should have any effect on GP3 operation.
However, I don't know the details on how meProg works. Is it possible that what it's actually programming into the chip is STILL what the code says - the default config for the 12F683 is MCLR enabled?

I guess you can always try that by changing the oscillator setting in meProg and program the chip, if it STILL runs then there's something going on with the CONFIG bits not being programmed to the settings showed in meProg.

I'm sorry for not having a definitive answer.

/Henrik.

[aerostar]

I have this in my program (PBP2.60C) and am using GP3 as an input and it works fine.

@ DEVICE PIC12F683, intrc_osc_noclkout, wdt_on, mclr_off, protect_off , bod_on

INCLUDE "ALLDIGITAL.pbp"

The ALLDIGITAL.pbp just makes sure I have everything set as digital.


The problem is that the PBP assembler uses mclr and mpasm uses MCLRE , see the .inc file

;****************************************************************
;*  12F683.INC                                                  *
;*                                                              *
;*  By        : Leonard Zerman, Jeff Schmoyer                   *
;*  Notice    : Copyright (c) 2005 microEngineering Labs, Inc.  *
;*              All Rights Reserved                             *
;*  Date      : 08/31/05                                        *
;*  Version   : 2.46a                                           *
;*  Notes     :                                                 *
;****************************************************************
        NOLIST
    ifdef PM_USED
        LIST
        include 'M12F683.INC'	; PM header
        device  pic12F683, intrc_osc_noclkout, wdt_on, mclr_on, protect_off
        XALL
        NOLIST
    else
        LIST
        LIST p = 12F683, r = dec, w = -302
        INCLUDE "P12F683.INC"	; MPASM  Header
        __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON & _CP_OFF
        NOLIST
    endif
        LIST

[mpgmike]

"device pic12F683, intrc_osc_noclkout, wdt_on, mclr_on, protect_off"
"__config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON & _CP_OFF"

I believe to use the MCLRE pin as a digital input these 2 lines must read "mclr_off" and "_MCLRE_OFF"

Mike

[aerostar]

"device pic12F683, intrc_osc_noclkout, wdt_on, mclr_on, protect_off"
"__config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON & _CP_OFF"

I believe to use the MCLRE pin as a digital input these 2 lines must read "mclr_off" and "_MCLRE_OFF"

Mike

But ONLY if you always want it OFF - and then have to remember to change it in the program, when you want it on.

The inc file is for general use, and idealy should be left unchanged, - you use the config statements in your program to over ride, as per the statement at top of post 3

@ DEVICE PIC12F683, intrc_osc_noclkout, wdt_on, mclr_off, protect_off , bod_on

[JakeMend]

I found out what to do. I need to reset the configuration file by inserting this code into beginning of the program

#config
__config _mclre_off
#endconfig

The pin 4 (bit 3) will now be an INPUT with an internal pull-up resistor.

NOTE: The underline before the config is a double underline __ and not a single underline_

There is a space after the config and before the _mclre


Thank you, Henrik, for your response.

[richard]

#config
__config _mclre_off
#endconfig

can be a bad move , all "unmentioned" config fuse settings will revert to default settings when the chip is erased


that means your config becomes possibly not whats really intended

#CONFIG
__config _EXTRC & _WDT_ON & _PWRTE_OFF & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOD_ON & _IESO_ON & _FCMEN_ON
#ENDCONFIG


imho its best to set the lot the way you intend

[JakeMend]

I want to sincerely thank all of the people who responded with advice and suggestions.

I not only got the initial problem solved, but I learned some things that I probably would not have figured out on my own that will save me from more problems in the future.

Thanks,

-Jake

[HenrikOlsson]

That's great news Jake!
Please stick around, tell us about your project, participate in the discussions and ask questions (preferrably ones that haven't been answered 100 times already), it's gotten very quiet here lately and we could use some new blood!

/Henrik.

[JakeMend]

I don't know about new blood or even new problems, but I have lots of old versions of both that I will be grateful to share.

Thanks,

-Jake