/**LED闪烁*led.s*/ #define GPJ0CON 0xE0200240 #define GPJ0DAT 0xE0200244 .global _start                //把 _start 链接属性改为外部_start:    //第一步 ：把0x1111 1111写入 0xe0200240(gpj0con)    ldr r0, =0x11111111   //这里ldr 为伪指令     ldr r1,    =GPJ0CON    str r0, [r1]          //寄存器间接寻址 将r0的值给ri所指地址的内存中        flash:    //第二部：把 0x0写入0xe0200244（GPJ0DAT） 点亮    //ldr r0, =0x28//  第一种 缺陷是需要人为计算设定值  可阅读型差            ldr r0, =(0<<3) |(0<<4)| (0<<5)// 等效于 0b0010_1000 即 0x28    ldr r1, =GPJ0DAT    str r0, [r1]            //点亮    //第三步: 延迟    bl delay                //使用bl进行调用可以将当前执行地址存入lr        //第四部：灭    //ldr r0, =0x28//  第一种 缺陷是需要人为计算设定值  可阅读型差            ldr r0, =(1<<3) |(1<<4)| (1<<5)    ldr r1, =GPJ0DAT    str r0, [r1]            //熄灭    bl delay        b flash                           b .                       //写一个死循环 防止CPU跑飞    delay:    ldr r2, =1000000    ldr r3, =0delay_loop:    sub r2, r2, #1      //r2=r2-1    cmp r2, r3        //cmp 比较r2 r3 如果相等 Z 为1    bne delay_loop    //bne 为当Z为1时执行跳转  bne 为 b+后缀    mov pc, lr          //函数调用返回  mov 为 寄存器间寻址

 反汇编

led.elf:     file format elf32-littlearmDisassembly of section .text:00000000 <_start>:   0:    e59f0044     ldr    r0, [pc, #68]    ; 4c 
     
         4:    e59f1044     ldr    r1, [pc, #68]    ; 50 
      
          8:    e5810000     str    r0, [r1]0000000c 
       
        :   c:    e3a00000     mov    r0, #0  10:    e59f103c     ldr    r1, [pc, #60]    ; 54 
        
           14:    e5810000     str    r0, [r1]  18:    eb000005     bl    34 
         
            1c:    e3a00038     mov    r0, #56    ; 0x38  20:    e59f102c     ldr    r1, [pc, #44]    ; 54 
          
            24: e5810000 str r0, [r1] 28: eb000001 bl 34 
           
             2c: eafffff6 b c 
            
              30: eafffffe b 30 
             
              00000034 
              
               : 34: e59f201c ldr r2, [pc, #28] ; 58 
               
                 38: e3a03000 mov r3, #00000003c 
                
                 : 3c: e2422001 sub r2, r2, #1 40: e1520003 cmp r2, r3 44: 1afffffc bne 3c 
                 
                   48: e1a0f00e mov pc, lr 4c: 11111111 tstne r1, r1, lsl r1 50: e0200240 eor r0, r0, r0, asr #4 54: e0200244 eor r0, r0, r4, asr #4 58: 000f4240 andeq r4, pc, r0, asr #4Disassembly of section .ARM.attributes:00000000 <.ARM.attributes>: 0: 00001a41 andeq r1, r0, r1, asr #20 4: 61656100 cmnvs r5, r0, lsl #2 8: 01006962 tsteq r0, r2, ror #18 c: 00000010 andeq r0, r0, r0, lsl r0 10: 45543505 ldrbmi r3, [r4, #-1285] ; 0x505 14: 08040600 stmdaeq r4, {r9, sl} 18: Address 0x00000018 is out of bounds.