PIC16F685 RA4/RA5 pins

[Adrian]

I thought(!) I understood that PortA 4 & 5 on a PIC16F684 could be used as general purpose I/O pins with an internal oscillator. So far I have been unable to achieve this. I have this at the top of my programme:-

@_CONFIG INTOSCIO & _WDT_ON & MCRE_OFF & _CP_OFF
ANSEL = $00
OSCON = %01100001
CMCON0 = 7
TRISA = $00
TRISC = $00

All other pins work fine but A4 continues to display a pretty 1Mhz clock output and A5 just looks at me!
I've RTFM endlessly and tried several things including subtle changes to the oscillator configuration fuse to no avail. So, to stop premature baldness can someone tell me what the problem is!

Many thanks

Adrian

[mackrackit]

Not sure I remember, but I think the comparators on that chip are under the
CM1CON0 and CM2CON0 registers. And A4 is open collector.
http://www.picbasic.co.uk/forum/showthread.php?t=562

You may want to look at the inc file in MPASM to be sure.

[Adrian]

Thanks mackrackit but still no joy. I've tried the open collector thing and I believe the COMCON0 to be right. This is puzzling me. I would have thought there should not be clock on A4 when INTOSCIO is chosen as a fuse. I'll keep trying (or change the PIC type.....!!!!)

Adrian

[Acetronics2]

Hi,

May be the underscore befre INTOSCIO ... ???

_EXTRC_OSC_NOCLKOUT EQU H'3FFE'
_EXTRC_OSC_CLKOUT EQU H'3FFF'
_INTOSCIO EQU H'3FFC'
_INTOSC EQU H'3FFD'
_EXTRCIO EQU H'3FFE'
_EXTRC EQU H'3FFF'

Beer for everyone !!!

Alain

[Bruce]

@_CONFIG INTOSCIO & _WDT_ON & MCRE_OFF & _CP_OFF ; 5 errors here
ANSEL = $00
OSCON = %01100001 ; 1 error here
CMCON0 = 7 ; 1 (maybe 2) errors here
TRISA = $00
TRISC = $00

First person to find them all gets the beer...;o}

[Adrian]

Hi Alain

Sadly not, so no beer - not even a good Cotes du Rhone from E.Guigal........! Unfortunately this was a typo error on my post. It was correct in the programme. Rest of programme is fine but RA4/RA5 stubbornly refuse to do anything useful. If someone out there has a 16F684 I'd like them to try it!

adrian

[Adrian]

Sorry for wrong information. This should be Pic16F684 not 685. Must be getting tired. HOWEVER it still doesn't work!!

[Bruce]

It would be a bit different if it's not a 685. Try something like this, and make sure your
device programmer keeps your config settings. You'll also need to comment out the default
config setting in the 16F684.INC file for MPASM.

@ __CONFIG _INTOSCIO & _WDT_ON & _MCLRE_OFF & _CP_OFF

ANSEL = $00
OSCCON = %01100000
CMCON0 = 7
TRISA = $00
TRISC = $00