> I am creating a general macro for sending messages to an LCD display, and
> have run into a problem.
>
> Here's my code:
>
>     clrf    counter
> disloop    incf    counter,1    ;get next character position from table
>     movf    counter,0    ;put char position into W
>     call    mess2    ;get the character
>     movwf    datalines    ;send it to lcd
>     ;         housekeeping for LCD snipped
>     comf    datalines,0    ;end of table has 0xff marker, so I complement it
> and check for zero
>     btfsc status, z    ;complemented character = 0?
>     goto    exitaddr    ;yes, done
>     goto    disloop    ;no, not done, get next character.
> exitaddr                ;continue on
> mess2    addwf    pc,1
>     retlw    'H'
>     retlw    'I'
>     retlw    0xff
>
> The code does not take the branch to exit.  As I read the spec sheet, the
> comf command should set the z flag if the result is zero (ie, datalines
> contained 0xff before the comf command).
>
> What am I doing wrong?
>
> --
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>
>
>

>I am creating a general macro for sending messages to an LCD display, and
>have run into a problem.
>
>Here's my code:
>
>     clrf    counter
>disloop    incf    counter,1    ;get next character position from table
>     movf    counter,0    ;put char position into W
>     call    mess2    ;get the character
>     movwf    datalines    ;send it to lcd
>     ;         housekeeping for LCD snipped
>     comf    datalines,0    ;end of table has 0xff marker, so I complement it
>and check for zero
>     btfsc status, z    ;complemented character = 0?
>     goto    exitaddr    ;yes, done
>     goto    disloop    ;no, not done, get next character.
>exitaddr                ;continue on
>mess2    addwf    pc,1
>     retlw    'H'
>     retlw    'I'
>     retlw    0xff

>... Many of the datasheets have an Instruction Set Summary, which includes
> examples of usage.  For the instruction COMF, from the 16F84 datasheet:
>
> Example:  COMF REG1,0
> Description: The contents of register  f  are comple-mented.  If  d  is 0
> the result is stored in W. If  d  is 1 the result is stored back in register
> f .
>
> Before Instruction
> REG1 = 0x13
> After Instruction
> REG1 = 0x13
> W =0xEC
>
>
> Note that the datashet uses "0" and gives the example on the status of W
> after the instruction.  Not only that, but it says nothing of using the
> mnemonics "W" or "F" as the destination.
>
> I hardly think that someone using this syntax deserves to be "penalized" for
> doing so.  By this I mean that someone looking for advice, assistance, or
> information on how to improve his program's success should not be turned
> away by some of the better and more experienced programmers on this list
> simply for using information obtained from the Microchip datasheets.  That
> doesn't show these people how to improve their skills, that just shows the
> arrogance of others.
>
> --Andrew

>
> I am creating a general macro for sending messages to an LCD display, and
> have run into a problem.
>
> Here's my code:
>
>     clrf    counter
> disloop    incf    counter,1    ;get next character position from table
>     movf    counter,0    ;put char position into W
>     call    mess2    ;get the character
>     movwf    datalines    ;send it to lcd
>     ;         housekeeping for LCD snipped
>     comf    datalines,0    ;end of table has 0xff marker, so I complement it
> and check for zero
>     btfsc status, z    ;complemented character = 0?
>     goto    exitaddr    ;yes, done
>     goto    disloop    ;no, not done, get next character.
> exitaddr                ;continue on
> mess2    addwf    pc,1
>     retlw    'H'
>     retlw    'I'
>     retlw    0xff
>
> The code does not take the branch to exit.  As I read the spec sheet, the
> comf command should set the z flag if the result is zero (ie, datalines
> contained 0xff before the comf command).
>
> What am I doing wrong?