7segment.s

ARM 7-segment control

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

/* define symbol of program */
.set	DELAY_CNT,	0x1fffff

.text
.global _start

.code 32
_start:

/* setup PORT A */
start:		ldr	r0, =PORTA_DIR
		mov	r1, #0
		str	r1, [r0]
		
		ldr	r0, =PORTA_MUX
		ldr	r1, =0x3fff
		str	r1, [r0]
		
/* main program */
		ldr	r5, =PORTA_DATA
		mov	r2, #0
		mov	r3, #0
main_loop:	bl	seg7
		str	r3, [r5]
		ldr	r0, =DELAY_CNT
		bl	delay
		add	r2, r2, #1
		cmp	r2, #11
		subeq	r2, r2, r2
		b	main_loop

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

/* binary to 7segment coding subroutine */
seg7:		adr	r3, seg_table
		ldr	r3, [r3, +r2, lsl #2]
		mov	pc, lr

/* coding table */
seg_table:
.word		0x000000c0,0x000000f9, 0x000000a4, 0x000000b0, 0x00000099, 0x00000092, 0x00000082, 0x000000f8, 0x00000080, 0x00000090, 0x0000007f

.end