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flat assembler > Non-x86 architectures > PIC assembly IO help

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Tyler



Joined: 19 Nov 2009
Posts: 1216
Location: NC, USA
My objective is to light an LED. So far, I have the circuit ready and the program *almost* working. That's what I need help with. I want to set RA1 high, but while executing the following code, I tested all pins(in case I messed up on the numbering/positioning) with a multimeter, and none of the pins, other than Vdd and Vss, registered.

Is there a problem in my code? I noticed that when ran in a simulator, PORTA(0x05) never changes value, I assumed this was normal since it is not average memory, but it could also be the effect of a bug.

Code:
STATUS equ 03h
PORTA        equ 05h
PORTB        equ 06h
TRISA        equ 85h
TRISB        equ 86h


start
    call    init
main
        movlw   02h
 xorwf   PORTA,01h
   
    movlw   0ffh
        call    delay
       call    delay
       goto    main


init
; switch to bank 1
  bsf     STATUS,05h
; clear bit 1 to set RA1 to out
       bcf     TRISA,01h
; switch back
  bcf     STATUS,05h
  return


delay
     movwf   20h
wait
 decfsz  20h,01h
     goto    wait
        return
      
    end
    
Post 16 Jan 2011, 01:44
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edfed



Joined: 20 Feb 2006
Posts: 4203
Location: 2018
can the PORTA(5) be configured as you want? if you refer to the datasheet, maybe you will find a little line saying: porta bit 5 cannot be configured as output... something like that.

it is the case for the pic12F675, where some pin of GPIO that cannot be configured as input, a read on this pin will always be 1.
Post 20 Feb 2011, 10:19
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