ARM用汇编写一段有缘蜂鸣器播放天空之城的代码

以下是一段使用汇编语言编写的播放天空之城的代码：

.syntax unified
.cpu cortex-m0

.equ GPIOA, 0x48000000   // GPIOA寄存器地址
.equ RCC_AHBENR, 0x40021014   // RCC_AHBENR寄存器地址

.section .text
.global main

main:
    // 初始化GPIOA引脚和RCC时钟
    ldr r0, =RCC_AHBENR
    movs r1, #1
    str r1, [r0, #17]   // RCC_AHBENR中的GPIOA时钟启用
    ldr r0, =GPIOA
    movs r1, #1
    str r1, [r0, #0]   // GPIOA的第0个引脚设置为输出

    // 演奏天空之城
    ldr r0, =notes
    movs r1, #0
    movs r2, #0
play_note:
    ldrb r1, [r0, r2]   // 从音符数组中读取音符
    cmp r1, #0   // 如果读到0表示演奏结束
    beq end_play
    lsl r1, #2   // 将音符左移2位，以得到对应的频率
    movs r3, #100   // 设置蜂鸣器持续时间
    bl play_tone   // 播放音符
    adds r2, #1   // 移动到下一个音符
    b play_note

end_play:
    b .

play_tone:
    push {r4, lr}
    ldr r4, =GPIOA
    ldr r0, [sp, #4]   // 读取音符频率
    movs r1, #1
    str r1, [r4, #12]   // 设置引脚高电平
    movs r3, #0xA0000   // 计算延时时间
    mov r2, r3
delay:
    subs r2, #1
    bne delay
    movs r1, #0
    str r1, [r4, #12]   // 设置引脚低电平
    movs r3, #0xA0000   // 计算延时时间
    mov r2, r3
delay2:
    subs r2, #1
    bne delay2
    pop {r4, pc}

.section .data
notes:
    .byte 9, 9, 11, 9, 4, 7, 2, 4, 9, 9, 11, 9, 5, 8, 3, 5, 9, 9, 12, 11, 7, 9, 4, 7, 9, 9, 11, 9, 5, 8, 3, 5, 9, 9, 12, 11, 7, 9, 4, 7, 9, 9, 11, 9, 5, 8, 3, 5, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 9, 9, 11, 9, 4, 7, 2, 4, 9, 9, 11, 9, 5, 8, 3, 5, 9, 9, 12, 11, 7, 9, 4, 7, 9, 9, 11, 9, 5, 8, 3, 5, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 9, 9, 11, 9, 4, 7, 2, 4, 9, 9, 11, 9, 5, 8, 3, 5, 9, 9, 12, 11, 7, 9, 4, 7, 9, 9, 11, 9, 5, 8, 3, 5, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 9, 9, 11, 9, 4, 7, 2, 4, 9, 9, 11, 9, 5, 8, 3, 5, 9, 9, 12, 11, 7, 9, 4, 7, 9, 9, 11, 9, 5, 8, 3, 5, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 9, 9, 11, 9, 4, 7, 2, 4, 9, 9, 11, 9, 5, 8, 3, 5, 9, 9, 12, 11, 7, 9, 4, 7, 9, 9, 11, 9, 5, 8, 3, 5, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 12, 12, 9, 7, 4, 2, 4, 7, 12, 12, 9, 7, 5, 3, 5, 8, 12, 12, 11, 9, 7, 8, 9, 9, 12, 12, 11, 9, 7, 8, 7, 7, 9, 9, 11, 11, 9, 7, 8, 9, 9, 12, 12, 11, 9, 7, 8, 7, 7, 9, 9, 11, 11, 9, 7, 8, 12, 12, 11, 9, 7, 8, 9, 9, 12, 12, 11, 9, 7, 8, 7, 7, 9, 9, 11, 11, 9, 7, 8, 9, 9, 12, 12, 11, 9, 7, 8, 7, 7, 9, 9, 11, 11, 9, 7, 8, 12, 12, 11, 9, 7, 8, 9, 9, 12, 12, 11, 9, 7, 8, 7, 7, 9, 9, 11, 11, 9, 7, 8, 9, 9, 12, 12, 11, 9, 7, 8, 7, 7, 9, 9, 11, 11, 9, 7, 8, 7, 7, 5, 5, 4, 4, 2, 2, 0

该代码的实现方式是，通过将ARM芯片上的GPIOA引脚设置为输出，然后在该引脚上产生不同频率的矩形波来演奏音乐。在这里，我们使用了一个简单的音符数组来描述天空之城的曲目。