>From the datasheet:

Note: On a Power-on Reset, these pins are configured
as analog inputs and read as '0'.

EXAMPLE 3-1: INITIALIZING PORTA

  BCF STATUS, RP0 ;
  BCF STATUS, RP1 ; Bank0
  CLRF PORTA ; Initialize PORTA by
  ; clearing output
  ; data latches
  BSF STATUS, RP0 ; Select Bank 1
  MOVLW 0x06 ; Configure all pins
  MOVWF ADCON1 ; as digital inputs
  MOVLW 0xCF ; Value used to
  ; initialize data
  ; direction
  MOVWF TRISA ; Set RA<3:0> as inputs
  ; RA<5:4> as outputs
  ; TRISA<7:6>are always
  ; read as =920=92.


So, make sure you initialize the pins as digital pins and not inputs to
the ADC (which is what they are after reset).

Harold


> I feel pretty silly bringing up this problem, but I've tried
> everything I can think of.  I can't run
> the simple code snippet shown below in the MPLAB v7.50
> simulator.
>
> It is suppossed to set up all PORTA pins as outputs and send
> 0x0f to the port.  But after running this in MPSIM, PORTA
> contains 0x00 rather than 0x0f.
>
> I have checked that the processor include file is there, it
> defines PORTA correctly, and it is being used.  A Watch window
> correctly shows PORTA at it's 0x05 address.  MPSIM is set for
> the correct CPU, and specifiying a radix parameter has no
> effect.
>
> I tried creating a brand new project and source code files, but
> the result was the same.
>
> Have I run into a bug or did I miss something that is or should
> have been glaringly obvious?  Interestingly, it works if I
> change PORTA/TRISA to PORTD/TRISD.
>
> Thanks in Advance,
> Andrew
>
>
>
> 	processor     	16f877a		; list directive to define processor
> 	#include	P16F877A.INC	; processor specific variable definitions
>
> 	__CONFIG _CP_OFF & _WDT_OFF & _BODEN_ON & _PWRTE_ON & _HS_OSC &
> _LVP_OFF & _DEBUG_OFF & _CPD_OFF
>
>
> 	ORG     0x000			; processor reset vector
> 	bsf	STATUS, RP0
> 	clrf	TRISA ^ 0x80
> 	bcf	STATUS, RP0
> 	movlw	0x0f
> 	movwf	PORTA
> 	goto	$
>
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