2. S3C6410裸机程序，LED灯闪烁

 1 /*
 2  * 实现流水灯，LED1 LED2 LED3 LED4轮流被点亮熄灭
 3  */
 4 
 5 .global _start
 6 .section .text
 7 
 8 _start:
 9 
10     /*
11      * set the CPU to SVC32 mode
12      */
13     mrs r0,cpsr
14     bic r0,r0,#0x1f        @ clear the last 5 bits
15     orr r0,r0,#0xd3        @ 0b11010011, set the svc mod, and disable fiq irq
16     msr cpsr,r0
17 
18     /*
19      * flush v4 I/D cahces
20      */
21     mov r0,#0
22     mcr p15, 0, r0, c7, c7, 0        /* flush v3/v4 cache */
23     mcr p15, 0, r0, c8, c7, 0        /* flush the v4 TLB */
24 
25     /*
26      * disable MMU stuff and caches
27      */
28     mrc p15, 0, r0, c1, c0, 0
29     bic    r0, r0, #0x00002300    @ clear bits 13, 9:8 (--V- --RS)
30     bic    r0, r0, #0x00000087    @ clear bits 7, 2:0 (B--- -CAM)
31     orr    r0, r0, #0x00000002    @ set bit 2 (A) Align
32     orr    r0, r0, #0x00001000    @ set bit 12 (I) I-Cache
33     mcr    p15, 0, r0, c1, c0, 0
34 
35     /* peripheral port register address range set */
36     ldr r0, =0x70000000    @the base address of peripheral port is 0x70000000
37     orr r0, #0x13        @address range is 256M,  0x7000 0000 -- 0x7FFF FFFF
38     mcr p15,0,r0,c15,c2,4
39     
40     /* disable the watchdog */
41     ldr r0, =0x7E004000
42     mov r1, #0
43     str r1, [r0]
44     
45     b user_program
46 
47     /*
48      * LED1 <----> GPK4
49      * LED2 <----> GPK5
50      * LED3 <----> GPK6
51      * LED4 <----> GPK7
52      */
53 user_program:
54     /************** control the led ***************/
55     /* control led1 GPK4 */
56     ldr r0, =0x7F008800
57     ldr r1, =0x11110000
58     str r1, [r0]        /* set GPK4 GPK5 GPK6 GPK7 as output*/
59 
60     ldr r0, =0x7F008808
61     ldr r1, [r0]
62     bic r1, #0x00F0
63 
64     mov r2, #0xf
65 light_water:
66     orr r3,r1,r2,LSL #4
67     str r3, [r0]
68     bl delay
69     subs r2,r2,#1
70     moveq r2, #0xf
71     b light_water
72 
73 
74 delay:
75     mov r4,#0x20000
76 delay_loop:
77     subs r4,r4,#1
78     bne delay_loop
79     mov pc,lr    @return
80 
81 .end