; Scaling test
.equ    myint   = 54321         ; Value to be scaled
.equ    coeff   = 0.34567*65536 ; Scaling coefficient
;
        ldi     r16,low(myint)
        ldi     r17,high(myint)
        movw    r4,r16          ; r5r4 = myint = 54321
        
        ldi     r16,low(coeff)
        ldi     r17,high(coeff) ; r17r16 = coeff = 0.34567
        rcall   scale16
        rjmp    PC

;--------------------------------------------------------------------
; Scales unsigned int r5:r4 by r17:r16 value presented as unsigned fractional (0000 = 0, FFFF = 0.99998)
; Result stored in r9:r8
; 14 program words, 17 clocks + ret
; 
scale16:
        clr     r2

        mul	r5,r17
        movw    r8,r0
        mul     r4,r16
        movw    r6,r0
        mul     r5,r16
        add     r7,r0
        adc     r8,r1
        adc     r9,r2
        mul     r4,r17
        add     r7,r0
        adc     r8,r1
        adc     r9,r2	; r9r8 = 54321*0.34567=~0x4958=18776

        ret