Lorick wrote:

> I pulled the reset pin up to VCC and had it set to use
> the internal RC so I didn't have anthing else in the demo circuit at all.

How does the PIC get a clock source when the 'F' series chips don't have
an internal clock?

>
> ;**********************************************************
> ;*  DEMO877.ASM
> ;**********************************************************
> ;*  Microchip Technology Incorporated
> ;*  16 December 1998
> ;*  Assembled with MPASM V2.20
> ;**********************************************************
> ;*  This program configures the A/D Module to convert on
> ;*  A/D channel 0 (the potentiometer) and display the
> ;*  results on the LEDS on PORTC.  Make sure that the DIP
> ;*  switch SW3 has all switches in the ON position.
> ;**********************************************************
>
>  list p=16f877
>
>  ; Include file, change directory if needed
>  include "p16f877.inc"
>
>  ; Start at the reset vector
>      org 0x000
>      nop
> Start
>      banksel PORTC
>      clrf PORTC                  ;Clear PORTC
>      movlw B'01000001'     ;Fosc/8, A/D enabled
>      movwf ADCON0
>
>      banksel OPTION_REG
>      movlw B'10000111'      ;TMR0 prescaler, 1:256
>      movwf OPTION_REG
>      clrf TRISC                     ;PORTC all outputs
>      movlw B'00001110'       ;Left justify,1 analog channel
>      movwf ADCON1           ;VDD and VSS references
>
>      banksel PORTC
>
> Main
>      btfss INTCON,T0IF     ;Wait for Timer0 to timeout
>      goto Main
>      bcf  INTCON,T0IF
>
>      bsf ADCON0,GO         ;Start A/D conversion
>     Wait
>      btfss PIR1,ADIF           ;Wait for conversion to complete
>      goto Wait
>      movf ADRESH,W         ;Write A/D result to PORTC
>      movwf PORTC              ;LEDs
>

This next instruction will clear the value just written previously to
PORTC so you will always see no leds lit. Try deleting it.

>      clrf PORTC


>     WaitPush
>      btfss PORTB,0
>      goto WaitPush
>

Delete this next instruction also, it's not needed.

>      movwf PORTC


>      goto Main                      ;Do it again
>
>  end


--
Best regards

Tony

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