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'Bug in posted MOMA code?? - fixed'
1998\11\10@005817 by Morgan Olsson

picon face
Good morning.
Amazing what a good night sleep can remove bugs from your brain.

In the case of adding low byte gave zero but no carry as result, that Z
flag would cause highest byte to increment, as middle byte inc was skipped.
Fixed now below.
Should work, not compiled yet.

I'm sorry for thoose who tested MOMA with the erroneous sum routine...


Sum16:  ;commented in english
;Summs a interval of 2-byte variables to 3-byte T4:T3:T2
;MSB at adress of LSB +1.
;Before call, state in W the total number of 2byte variables to sum.
;And set FSR to point to the low byte of first variabe to sum.
;(FSR may point in bank 0 or 1 regardless of back select :) )
;FSR get incremented by two for each variable summed

       movwf T1        ;store number of variables to temp reg T1
        movlw  4          ;Preload destination with 000004h
       movwf T2           ;(New; for correct rounding in this application
       clrf T3    ;where we sum 8 variables;
       clrf T4    ;For normal SUM use we clear all T4:T3:T2)
       movf INDF,W     ;Get low byte,
       addwf T2,F      ;and add to low byte result
       ifcc            ;If carry clear,                        <<<<<<<< Changed
          goto Sum16lhigh; go right on with high byte   <<<<<<<<< New
       incf T3,F       ;If carry: inc middle byte result;
       ifzs            ;If that wrapped to Zero,
         incf T4,F     ; inc high byte result too.
       incf FSR,F      ;Point to MSB in,
       movf INDF,W     ;get it,
       addwf T3,F      ;and add to middle byte result
       ifcs            ;If carry,
         incf T4,F     ; inc high byte result

       incf FSR,F      ;Point to next variable low byte
       decfsz T1,F     ;Decrease counter for variables to add,
         goto Sum16loop;if not done add next variable
       return      ;the sum +4 is now in T4:T3:T2
       Morgan Olsson                   ph  +46(0)414 70741
       MORGANS REGLERTEKNIK            fax +46(0)414 70331
       H€LLEKS           (in A-Z letters: "HALLEKAS")
       SE-277 35 KIVIK, SWEDEN     

1998\11\10@065618 by Stefan Sczekalla-Waldschmidt


Interesting how many minds will come to similar solutions ...
I should have read all messages first before writing answers already
given :)

Kind regards

       Stefan Sczekalla-Waldschmidt

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