PIC Microcontoller Math Method

Scale 8 bits to a percent

Dmitry Kiryashov says: Possible realization of 1 + 1/256 + ... correction.

;1/256 * (1 + 1/256) =~ 0.999985 / 255 ;
scale255to100: ;25 = 16+8+1
 clrf temp ;int
 clrf temp1 ;frac
 addwf temp,F ;1
 rrf temp,F ;/2
 rrf temp1,F
 rrf temp,F ;/4
 rrf temp1,F
 rrf temp,F ;/8
 rrf temp1,F
 addwf temp,F ;8
 rrf temp,F ;/16
 rrf temp1,F
 addwf temp,F ;16
 rrf temp,F ;/32
 rrf temp1,F
 rrf temp,W ;/64
 rrf temp1,F
;
; movwf temp2 ;1/256/256 if longer tail
; movwf temp3 ;1/256/256/256 is required
; etc...
;
 addwf temp1,F ;1 + 1/256 correction
 btfss temp1,7 ;either round if >= 0.5
 skpnc ;or take carry
 addlw 1 ;temp1 holds frac part
;
; movwf temp ;answer is either W or temp
 return
If >=0.5 correction isn't required <btfss temp1,7> line
should be commented.

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