led.s

ARM LED control Assembly example

/* define symbols */
.equ	PORTA_MUX,	0x09000000
.equ	PORTA_DATA,	0x09001600
.equ	PORTA_DIR,	0x09001604

/* define symbol of program */
.set	DELAY_LED,	0xfffff

.text
.global _start

.code 32
_start:
/* setup PORT A */
start:		ldr	r0, =PORTA_MUX
		ldr	r1, =0x3fff
		str	r1, [r0]
		
		ldr	r0, =PORTA_DIR
		mov	r1, #0
		str	r1, [r0]

/* main program */
		ldr	r3, =PORTA_DATA
		mov	r2, #0
led_loop:	str	r2, [r3]
		ldr	r0, =DELAY_LED
		bl	delay
		add	r2, r2, #1
		b	led_loop

/* delay subroutine */
delay:		subs	r0, r0, #1
		bne	delay
		mov	pc, lr

.end