michael brown wrote:
> wouter van ooijen wrote:
>   
>>>> Note that this code still requires that all jump table
>>>>         
>>> entries are in
>>>       
>>>> the same 256-instructions page. For a jumptable that crosses a page
>>>> boundary (hence for all >256 entries tables) you will have to
>>>> calculate the value to load into PCLATH.
>>>>         
>>> Unless I'm really missing something here, I don't understand
>>> why you say
>>> that.  His technique takes into consideration that a page is being
>>> crossed and appropriately increments PCLATH by 1 when that is
>>> happening.
>>>       
>> Sorry, you are right. I did not look well enough.
>>     
You ave anymore got a point: the jump table must be less than 256 
byte... I have not considered this...
Bigger tables needs a little more complex code but I think that is not 
the case of the OP
>
> I don't know why Microchip doesn't tout doing it this way.  It's only a 
> few instructions more and makes the table floatable.    Here is how I 
> did it for a character table on a 16F88:
>
> get_msg_char
>                 movfw       msg_ptr             ; get desired offset from beginning of string
>                 btfss       PORTA, DIRECTION    ; Check direction
>                  sublw      message_size - 1    ; When going CCW, we must fetch letters in reverse order
>                 addlw       3
>                 addwf       PCL, W              ; Add offset and current PCL
>                 skpnc                           ; Check for page crossing
>                  incf       PCLATH, F           ;  and compensate for it
>                 movwf       PCL                 ; Fetch the value
> message         dt "MESSAGE TEXT GOES HERE"
> message_size    equ     $ - message
>
> I intentionally forced the text to cross a page boundary and all was 
> well.  The 3 being added is for the skpnc, incf and movwf instructions.
>
>   
Your code works but i dont like it:
the ADDLW 3 is in the category of dangeours tricks :-)
just reordering the instructions you can eliminate it and have a more 
readable code

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