; ce programme est pour l'assembleur RealView (Keil)
	thumb
	area  moncode, code, readonly
	export timer_callback
	extern etat
;
E_POS	equ	0
E_TAI	equ	4
E_SON	equ	8
E_RES	equ	12
E_PER	equ	16

TIM3_CCR3	equ	0x4000043C	; adresse registre PWM	

timer_callback proc
	
	push{r4}
	
	ldr r1, =etat
	ldr r2, [r1, #E_POS]

	ldr r3, [r1,#E_TAI]
	cmp r2, r3
	beq	silence
	bne	son
son	ldr r4, [r1, #E_RES]
	ldr r3, [r1, #E_SON]
	ldrsh r3, [r3, r2,lsl #1]
	
	add r3, r3, lsl #16
	mul r3, r3, r4
	lsr r3, #16
	;add r3, r3, r4
	;lsl r3, #1
	
	ldr r4, =TIM3_CCR3
	str r3, [r4]

	add r2,#1
	str r2,[r1, #E_POS]
	
silence	
	
	pop{r4}
	bx lr
	endp
	end