Phil wrote:

>On Wednesday 11 Jun 2003 12:06, you wrote:
>
>
>>It's easier to read and more informative to use includes and an
>>itemised CONFIG statement
>>
>>
>>
><cut>
>
>Now that I understand how to write to a port I thought that reading from a
>port would be just as easy, but it seems it's not.
>
>This code is based on that provided by Jinx but I seem to be missing
>something. The LED is always on no matter what the state of pin 18.
>
>Could someone put me on the right track?
>
>        PROCESSOR p16f628
>        INCLUDE p16f628.inc
>        __CONFIG _CP_OFF &_WDT_OFF &_BODEN_OFF &_PWRTE_ON &_INTRC_OSC_NOCLKOUT
>        ERRORLEVEL -302                         ; Don't care about the "bank bits" messages
>
>;****Set up the port****
>
>                bsf             STATUS,5                ;Switch to Bank 1
>                movlw   b'00000010'     ;Port A1 input the rest outputs
>                movwf   TRISA           ;to output.
>
>                movlw   07h                     ;set Port A1
>                movwf           CMCON           ;to digital mode
>
>                bcf             STATUS,5                ;Switch back to Bank 0
>
>
>                clrf            PORTA
>
>;****Turn the LED on if pin 18 is grounded****
>
>

Hi Phil,
So far, so good.

>Start           btfsc   PORTA, 1                ;wait for a.1 to ground
>                goto            Start
>
>                movlw   04h                     ;Turn on the LED
>                movwf   PORTA
>
>                goto            Start
>
>

OK, change it to this:

start:          btfss   PORTA,1                 ;is RA.1 high?
                goto    sw_low                  ;no
                movlw   04h                     ;yes
                movwf   PORTA                   ;turn LED on
                goto    start                   ;

sw_low:         clrf    PORTA                   ;turn LED off (this is the step you forgot!)
                goto    start                   ;


>                end
>
>--
>Regards,
>Phil.
>
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>
>

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