/* Write a function to convert a packed BCD number 
 * in register r24 into its binary equivalent.
 * Return 8-bit binary result in register r24.
 * For example if r24 = 32 then result r24 = 3 x 10 + 2
 *
 * Source: Beginners Introduction to the Assembly Language of ATMEL­AVR­Microprocessors
 *         http://www.ic.unicamp.br/~celio/mc404-2008/docs/beginner_avr.pdf 
 */

.INCLUDE <m328pdef.inc> 

BCDtoBINARY:
	; Conversion of packed BCD number to 8-bit Binary (0 to 99)
	push r15       ; save contents of registers modified by this subroutine
	in   r15, SREG
	push  r16
	push  r25

	mov   r25,r24  ; copy the number to another register.
	swap  r25      ; exchange upper and the lower nibbles
	cbr   r25,0xF0 ; clear upper BCD nibble
	cbr   r24,0xF0 ; clear lower BCD nibble
	ldi   r16,0x0A ; 10
	mul   r25,r16  ; r1:r0 = 10's place (result 0 to 90)
	add   r24,r0   ; add to 1's place

    pop   r25
	pop   r16
	out   SREG, r15
	pop   r15
	ret