我的汇编流水灯程序

.global    _start
.align    2
@.text

_start:
    mov ip, sp
    stmfd  {r0-r12, lr, pc}
    sub fp, ip, #4

    ldr r0, =0x7F008820
    ldr r3, =0xffff
    mvn r1, r3
    ldr r2, [r0]
    and r2, r1, r2
    str r2, [r0] @r3, r1

    ldr r1, =0x1111
    ldr r2, [r0]
    orr r2, r1, r2
    str r2, [r0]@r0-r3

    ldr r0, =0x7f008824
    mov r1, #0xf
    ldr r2, [r0]
    orr r2, r1, r2
    str r2, [r0]@r0-r3
    mov r4, #1
    mov r5, #1
    mov r6, #2

led_on:
    ldr r0, =0x7f008824
    mvn r1, r4
    ldr r2, [r0]
    and r2, r1, r2
    str r2, [r0]

    mov r0, #70
    bl delay

led_off:
    ldr r0, =0x7f008824
    mov r1, r4
    ldr r2, [r0]
    orr r2, r1, r2
    str r2, [r0]

    mov r0, #70
    bl delay

    mul r4, r4, r6
    cmp r4, #16
    moveq r4, #1

    add r5, r5, #1
    cmp r5, #25
    beq end
    b led_on

end:
    sub sp, fp, #56
    ldmfd sp, {r0-r11, sp, pc}