Hi,

James Williams wrote:
<snip>
Any ideas.  I know that I am not crossing the 256 byte barrier.  I know that
is has something to do with the size of the goto instruction, but I can't
seem to get the jump sizes right.
<snip>


Well for the 18xx series one needs to multiply with *4* for an
goto table :) neat eh.
Here's an 'ugly' an macro that actually worked :)
Table_temp is an dedicated byte of access ram, modify until
you think it has the functionality you need.
Note: does not care about PCLATHU ! ( no pic's has that amount of program
mem yet )
Usage:

TABLE_JUMP_GTO Label_StartOfTable



;+++++
;       TABLE_JUMP_GTO Calculates an eventual table boundary crossing
;       set's up the PCLATH register correctly
;       Offset must be in w-reg, offset 0 jumps to the next instr.
;       To be used OUTSIDE isr ONLY, modified for 18x series and a table
with gotos
;       i.e. the number in w is quadrupled.
;
TABLE_JUMP_GTO  MACRO   TableStart
        MOVWF   Table_Temp,A    ; save wanted offset
        RLNCF   Table_Temp,F,A  ; multiply with 2 ( for 18x pic's ) ( bit 7
into bit 0 )
        RLNCF   Table_Temp,F,A  ; multiply with 2 again ( for 18x pic's ) (
bit 6 into bit 0, bit 0 into bit 1 )
        MOVLW   HIGH(TableStart); get high adress for table ( first adress
after macro )
        BTFSC   Table_Temp,0,A  ; lowest bit set means add one
        ADDLW   0x01
        BTFSC   Table_Temp,1,A  ; second bit set means add two
        ADDLW   0x02
        MOVWF   PCLATH,A        ; set high adress
        MOVLW   b'11111100'     ; mask out lowest two bits
        ANDWF   Table_Temp,F,A
        MOVLW   LOW(TableStart) ; get low adress ( of first instr. after
macro )
        ADDWF   Table_Temp,W,A  ; add offset
        BTFSC   STATUS,C        ; page crossed ? ( 256 byte )
        INCF    PCLATH,F,A      ; yes add one to high adress
        MOVWF   PCL,A           ; And jump
        ENDM

Have fun,

/Tony

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