LED三盏灯的交替闪烁

.text 
.global _start
_start: 
	/* 1. led灯的初始化 */
	/* 1.1 使能GPIOE、DPIOF外设控制器的时钟 */
	ldr r0, =0x50000A28
	ldr r1, [r0]
	orr r1, r1, #(0x3 << 4)
	str r1, [r0]
 
	/* 1.2 设置PE10、PE8、PF10引脚为输出模式 */
	ldr r0, =0x50006000
	ldr r1, [r0]
	bic r1, r1, #(0x3 << 16)
	orr r1, r1, #(0x1 << 16)
	bic r1, r1, #(0x3 << 20)
	orr r1, r1, #(0x1 << 20)
	str r1, [r0]
 
	ldr r0, =0x50007000
	ldr r1, [r0]
	bic r1, r1, #(0x3 << 20)
	orr r1, r1, #(0x1 << 20)
	str r1, [r0]
 
	/* 1.3 设置PE10、PE8、PF10引脚为推挽输出 */
	ldr r0, =0x50006004
	ldr r1, [r0]
	bic r1, r1, #(0x1 << 8)
	bic r1, r1, #(0x1 << 10)
	str r1, [r0]
 
	ldr r0, =0x50007004
	ldr r1, [r0]
	bic r1, r1, #(0x1 << 10)
	str r1, [r0]
 
	/* 1.4 设置PE10、PE8、PF10引脚为低速模式 */
	ldr r0, =0x50006008
	ldr r1, [r0]
	bic r1, r1, #(0x3 << 16)
	bic r1, r1, #(0x3 << 20)
	str r1, [r0]
	
	ldr r0, =0x50007008
	ldr r1, [r0]
	bic r1, r1, #(0x3 << 20)
	str r1, [r0]
 
	/* 1.5 设置PE10、PE8、PF10引脚禁止上拉和下拉电阻 */
	ldr r0, =0x5000600C
	ldr r1, [r0]
	bic r1, r1, #(0x3 << 16)
	bic r1, r1, #(0x3 << 20)
	str r1, [r0]
 
	ldr r0, =0x5000700C
	ldr r1, [r0]
	bic r1, r1, #(0x3 << 20)
	str r1, [r0]
 
	/* led1灯的初始化完成 */
loop:
	/* 设置PE10引脚输出高电平， 点亮LED1灯 */
	ldr r0, =0x50006014
	ldr r1, [r0]
	orr r1, r1, #(0x1 << 10)
	str r1, [r0]
 
	bl delay_1s
 
	/* 设置PE10引脚输出低电平， 熄灭LED1灯 */
	ldr r0, =0x50006014
	ldr r1, [r0]
	bic r1, r1, #(0x1 << 10)
	str r1, [r0]
 
	bl delay_1s
 
	/* 设置PF10引脚输出低电平， 点亮LED2灯 */
	ldr r0, =0x50007014
	ldr r1, [r0]
	orr r1, r1, #(0x1 << 10)
	str r1, [r0]
 
	bl delay_1s
 
	/* 设置PF10引脚输出低电平， 熄灭LED2灯 */
	ldr r0, =0x50007014
	ldr r1, [r0]
	bic r1, r1, #(0x1 << 10)
	str r1, [r0]
 
	bl delay_1s
 
	/* 设置PE8引脚输出高电平， 点亮LED3灯 */
	ldr r0, =0x50006014
	ldr r1, [r0]
	orr r1, r1, #(0x1 << 8)
	str r1, [r0]
	
	bl delay_1s
	
	/* 设置PE8引脚输出低电平， 熄灭LED3灯 */
	ldr r0, =0x50006014
	ldr r1, [r0]
	bic r1, r1, #(0x1 << 8)
	str r1, [r0]
	
	bl delay_1s
 
	b loop
 
@ 大概1s的延时函数
delay_1s:
	mov r3, #0x10000000
	mm:
	cmp r3, #0
	subne r3, r3, #1
	bne mm
	mov pc, lr
 
.end