ARM裸机之定时器中断

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;     //BWSCONp[1] = 0x00000700;     //BANKCON0p[2] = 0x00000700;     //BANKCON1p[3] = 0x00000700;     //BANKCON2p[4] = 0x00000700;     //BANKCON3p[5] = 0x00000700;     //BANKCON4p[6] = 0x00000700;     //BANKCON5p[7] = 0x00018005;     //BANKCON6p[8] = 0x00018005;     //BANKCON7/* REFRESH,* HCLK=12MHz:  0x008C07A3,* HCLK=100MHz: 0x008C04F4*/p[9]  = 0x008C04F4;p[10] = 0x000000B1;     //BANKSIZEp[11] = 0x00000030;     //MRSRB6p[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*/#define	GPB5_out	(1<(5*2))#define	GPB6_out	(1<(6*2))#define	GPB7_out	(1<(7*2))#define	GPB8_out	(1<(8*2))#define	GPB5_msk	(3<(5*2))#define	GPB6_msk	(3<(6*2))#define	GPB7_msk	(3<(7*2))#define	GPB8_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 = 99TCFG1  = 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。