I suspect that is input only type of pin.
You still can try manipulate it by switching
pull ups on and off.



laura capaldi wrote:
> 
> I've been struggling to figure out why I can set GP1, GP2, GP4 and GP5 without trouble but I can't get GP3 to set. Set meaning I can't get it to go high and turn on an LED. I'm using a 12F675. I suspect it has something to do with my config bits because MCLR is on GP3. Here's the simple program I wrote. I'm hoping someone can help me spot my bug. Thanks.
> 
> ; test1
>  list      p=12F675
>  #include <p12f675.inc>
>  __CONFIG  _CP_OFF & _WDT_OFF & _BODEN_ON & _PWRTE_ON & _INTRC_OSC_NOCLKOUT & _MCLRE_OFF & _CPD_OFF
> #define Bank0  0x00
> #define Bank1  0x80
>  cblock 0x20
>  ncount
>  mcount
>  ocount
>  endc
>  ORG     0x000
>  nop
>  goto    Init
>  ORG 0x004
>  return
> Init
>  banksel Bank1
>  movwf   OSCCAL
>  movlw B'00000001' ; set direction so all pins except GP0 are output pins
>  movwf TRISIO  ; so GP0 is input pin
>  movlw b'00010001'
>  movwf ANSEL  ; make GP0 (AN0) be analog input and Fosc/8 for A/D conversion clock
>  banksel Bank0
>  movlw b'111'
>  movwf CMCON  ; disable comparator
>  movlw b'00000001' ;
>  movwf ADCON0   ; Select AN0 as a2d channel, Left justified & enables A/D
>  NOP      ; Give 4 uS delay before starting A/D
>  NOP
>  NOP
>  NOP
>  bsf ADCON0,GO   ; Start A/D
> Main
>  call NOon
>  call delay
>  call GP1on
>  call delay
>  call NOon
>  call delay
>  call GP2on
>  call delay
>  call NOon
>  call delay
>  call GP3on
>  call delay
>  call NOon
>  call delay
>  call GP4on
>  call delay
>  call NOon
>  call delay
>  call GP5on
>  call delay
>  goto Main
> NOon
>  movlw b'00000000'
>  movwf GPIO
>  return
> 
> GP1on
>  movlw b'00000010'
>  movwf GPIO
>  return
> GP2on
>  movlw b'00000100'
>  movwf GPIO
>  return
> GP3on
>  movlw b'00001000'
>  movwf GPIO
>  return
> GP4on
>  movlw b'00010000'
>  movwf GPIO
>  return
> GP5on
>  movlw b'00100000'
>  movwf GPIO
>  return
> delay
>  movlw 0x10
>  movwf mcount
> loadn
>  movlw 0xFF
>  movwf ncount
> loado
>  movlw 0xFF
>  movwf ocount
> repeat
>  decfsz ocount,f
>  goto repeat
>  decfsz ncount,f
>  goto loado
>  decfsz mcount,f
>  goto loadn
>  return
> 
>  END
> 
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