2. S3C6410裸机程序，LED灯闪烁
继续上一篇：1. 构建S3C6410裸机开发环境，并使用GPIO控制LED灯
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
