.global fp4816_to_float


fp4816_to_float:
;	fp4816_t (int64)	r18:r25
;	return:	float		r22:r25
;
;	work:	float	r12:r15
;			exp		r17
	push	r17
	push	r16
	push	r15
	push	r14
	push	r13
	push	r12
	
	eor		r15,	r15
	eor		r14,	r14
	eor		r13,	r13
	eor		r12,	r12

	cp		r18,	r1
	cpc		r19,	r1
	cpc		r20,	r1
	cpc		r21,	r1
	cpc		r22,	r1
	cpc		r23,	r1
	cpc		r24,	r1
	cpc		r25,	r1
	breq	_exit

	ldi		r17,	0x2f	; 47d

	; value < 0 : SIGN=1, value * -1
	sbrs	r25,	7
	rjmp	_l1

	ldi		r16,	0x80
	or		r15,	r16
	com		r25
	com		r24
	com		r23
	com		r22
	com		r21
	com		r20
	com		r19
	com		r18

	ldi		r16,	0x01
	add		r18,	r16
	adc		r19,	r1
	adc		r20,	r1
	adc		r21,	r1
	adc		r22,	r1
	adc		r23,	r1
	adc		r24,	r1
	adc		r25,	r1
	
	
_l1:
	; exponent bestimmen
	tst		r25
	brne	_l2

	mov		r25,	r24
	mov		r24,	r23
	mov		r23,	r22
	mov		r22,	r21
	mov		r21,	r20
	mov		r20,	r19
	mov		r19,	r18
	eor		r18,	r18

	ldi		r16,	0x08
	sub		r17,	r16

	rjmp	_l1
	
_l2:
	mov		r16,	r25
	andi	r16,	0x80
	brne	_l3
	
	clc
	rol		r18
	rol		r19
	rol		r20
	rol		r21
	rol		r22
	rol		r23
	rol		r24
	rol		r25
	
	dec		r17
	
	rjmp	_l2

_l3:	
	; Mantisse schreiben
	mov		r12,	r23
	mov		r13,	r24
	mov		r14,	r25
	ldi		r16,	0x7F
	and		r14,	r16
	
	; exponent schreiben
	add		r17,	r16
	ldi		r16,	0x80
	sbrc	r17,	0
	or		r14,	r16
	lsr		r17
	or		r15,	r17
	
_exit:
	movw	r22,	r12
	movw	r24,	r14

	pop		r12
	pop		r13
	pop		r14
	pop		r15
	pop		r16
	pop		r17
	ret