ARM裸机之定时器中断

来源：互联网发布：深圳云和数据招聘编辑：程序博客网时间：2024/04/29 04:18

转载请注明出处：http://blog.csdn.net/ruoyunliufeng/article/details/21464145

本文开发环境mini2440，实现目标：裸机实现定时器中断使LED0以1秒闪烁。

int.c函数

/* * init.c: 进行一些初始化 */#include "s3c24xx.h"void disable_watch_dog(void);void clock_init(void);void memsetup(void);void copy_steppingstone_to_sdram(void);void init_led(void);void timer0_init(void);void init_irq(void);/* * 关闭WATCHDOG，否则CPU会不断重启 */void disable_watch_dog(void){    WTCON = 0;  // 关闭WATCHDOG很简单，往这个寄存器写0即可}#define S3C2410_MPLL_200MHZ     ((0x5c<<12)|(0x04<<4)|(0x00))#define S3C2440_MPLL_200MHZ     ((0x5c<<12)|(0x01<<4)|(0x02))/* * 对于MPLLCON寄存器，[19:12]为MDIV，[9:4]为PDIV，[1:0]为SDIV * 有如下计算公式： *  S3C2410: MPLL(FCLK) = (m * Fin)/(p * 2^s) *  S3C2410: MPLL(FCLK) = (2 * m * Fin)/(p * 2^s) *  其中: m = MDIV + 8, p = PDIV + 2, s = SDIV * 对于本开发板，Fin = 12MHz * 设置CLKDIVN，令分频比为：FCLK:HCLK:PCLK=1:2:4， * FCLK=200MHz,HCLK=100MHz,PCLK=50MHz */void clock_init(void){    // LOCKTIME = 0x00ffffff;   // 使用默认值即可    CLKDIVN  = 0x03;            // FCLK:HCLK:PCLK=1:2:4, HDIVN=1,PDIVN=1    /* 如果HDIVN非0，CPU的总线模式应该从“fast bus mode”变为“asynchronous bus mode” */__asm__(    "mrc    p15, 0, r1, c1, c0, 0\n"        /* 读出控制寄存器 */    "orr    r1, r1, #0xc0000000\n"          /* 设置为“asynchronous bus mode” */    "mcr    p15, 0, r1, c1, c0, 0\n"        /* 写入控制寄存器 */    );    /* 判断是S3C2410还是S3C2440 */    if ((GSTATUS1 == 0x32410000) || (GSTATUS1 == 0x32410002))    {        MPLLCON = S3C2410_MPLL_200MHZ;  /* 现在，FCLK=200MHz,HCLK=100MHz,PCLK=50MHz */    }    else    {        MPLLCON = S3C2440_MPLL_200MHZ;  /* 现在，FCLK=200MHz,HCLK=100MHz,PCLK=50MHz */    }}/* * 设置存储控制器以使用SDRAM */void memsetup(void){    volatile unsigned long *p = (volatile unsigned long *)MEM_CTL_BASE;    /* 这个函数之所以这样赋值，而不是像前面的实验(比如mmu实验)那样将配置值     * 写在数组中，是因为要生成”位置无关的代码”，使得这个函数可以在被复制到     * SDRAM之前就可以在steppingstone中运行     */    /* 存储控制器13个寄存器的值 */    p[0] = 0x22011110;     //BWSCON    p[1] = 0x00000700;     //BANKCON0    p[2] = 0x00000700;     //BANKCON1    p[3] = 0x00000700;     //BANKCON2    p[4] = 0x00000700;     //BANKCON3    p[5] = 0x00000700;     //BANKCON4    p[6] = 0x00000700;     //BANKCON5    p[7] = 0x00018005;     //BANKCON6    p[8] = 0x00018005;     //BANKCON7    /* REFRESH,     * HCLK=12MHz:  0x008C07A3,     * HCLK=100MHz: 0x008C04F4     */    p[9]  = 0x008C04F4;    p[10] = 0x000000B1;     //BANKSIZE    p[11] = 0x00000030;     //MRSRB6    p[12] = 0x00000030;     //MRSRB7}void copy_steppingstone_to_sdram(void){    unsigned int *pdwSrc  = (unsigned int *)0;    unsigned int *pdwDest = (unsigned int *)0x30000000;    while (pdwSrc < (unsigned int *)4096)    {        *pdwDest = *pdwSrc;        pdwDest++;        pdwSrc++;    }}/* * LED1,LED2,LED4对应GPB5、GPB6、GPB7、GPB8 */#defineGPB5_out(1<<(5*2))#defineGPB6_out(1<<(6*2))#defineGPB7_out(1<<(7*2))#defineGPB8_out(1<<(8*2))#defineGPB5_msk(3<<(5*2))#defineGPB6_msk(3<<(6*2))#defineGPB7_msk(3<<(7*2))#defineGPB8_msk(3<<(8*2))void init_led(void){// LED1,LED2,LED3,LED4对应的4根引脚设为输出GPBCON &= ~(GPB5_msk | GPB6_msk | GPB7_msk | GPB8_msk);GPBCON |= GPB5_out | GPB6_out | GPB7_out | GPB8_out;}/* * Timer input clock Frequency = PCLK / {prescaler value+1} / {divider value} * {prescaler value} = 0~255 * {divider value} = 2, 4, 8, 16 * 本实验的Timer0的时钟频率=100MHz/(99+1)/(16)=62500Hz * 设置Timer0 0.5秒钟触发一次中断： */void timer0_init(void){    TCFG0  = 99;        // 预分频器0 = 99    TCFG1  = 0x03;      // 选择16分频    TCNTB0 = 62500;     // 0.5秒钟触发一次中断    TCON   |= (1<<1);   // 手动更新    TCON   = 0x09;      // 自动加载，清“手动更新”位，启动定时器0}/* * 定时器0中断使能 */void init_irq(void){    // 定时器0中断使能    INTMSK   &= (~(1<<10));}

中断函数interrupt.c

#include "s3c24xx.h"void Timer0_Handle(void){    /*     * 每次中断令4个LED改变状态,亮灭交替     */    if(INTOFFSET == 10)    {        GPBDAT = ~(GPBDAT & (0xf << 5));    }    //清中断    SRCPND = 1 << INTOFFSET;    INTPND = INTPND;}

主函数main.c

int main(void){    while(1);    return 0;}

本程序根据韦东山嵌入式linux应用开发修改，适用于mini2440做定时器中断实验。

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