; Div16_8B 
; Version 1.0
; Date: November 11, 2014
; Written By : Yoseph Yegezu


.INCLUDE <m328pdef.inc>

			
.CSEG


.DEF Denominator=R19
.DEF NL=r24
.DEF NH=r25
.DEF QL=r21
.DEF QH=r22

.ORG 0x0000



	ldi r16,0xAA
	mov NH,r16
	mov NL,r16
	ldi Denominator, 0x55
	//Call the 16 bit by 8 bit division
    rcall Div16_8
	ret	

/************************************
 * subroutine divides unside 16bit by 8bit
 * Quotient = Numerator/Denominator    *
 * r22:r21  = r25:r24 / r19        *
 ***************************************/
Div16_8: 
  	clr  r22
	clr  r21         


// loop  L1 stops when the numerator - denominator = less than the demoninator

L1:
//QL is going to increment by 1, everytime L1 loops
	inc QL   //r22
	
//When QL reaches 255 or 0XFF and then goes back to 0, QH is going to increment by 1
	cpi r21,0
	brne No_Inc
	inc QH   //r22

	No_Inc:
	sub  r24,Denominator  // r19
	sbc  r25,r2

	brcc L1

//Since r21 is incremented by 1 when the loop began, after the loop r21 is decremented
	dec  QL  //r21

//Notice L1 is going to branch off when the numerator is no lnger divisiable by the denominator 
//Which means L1 is branching off when r24-denominator results in a negative value.
//Therefore, the denominator is going to be added to the r24 after the loop.
	
	add  r24,Denominator  //r24,r19
	adc  r25,r2
	
	
	ret