head.s文件
@****************************************************************************** @ File：head.S @ 功能：初始化，设置中断模式、管理模式的栈，设置好中断处理函数 @****************************************************************************** .extern main .text .global _start _start: @****************************************************************************** @ 异常向量，本程序中，除Reset和HandleIRQ外，其它异常都没有使用 @****************************************************************************** b Reset @ 0x04: 未定义指令中止模式的向量地址 HandleUndef: b HandleUndef @ 0x08: 管理模式的向量地址，通过SWI指令进入此模式 HandleSWI: b HandleSWI @ 0x0c: 指令预取终止导致的异常的向量地址 HandlePrefetchAbort: b HandlePrefetchAbort @ 0x10: 数据访问终止导致的异常的向量地址 HandleDataAbort: b HandleDataAbort @ 0x14: 保留 HandleNotUsed: b HandleNotUsed @ 0x18: 中断模式的向量地址 b HandleIRQ @ 0x1c: 快中断模式的向量地址 HandleFIQ: b HandleFIQ Reset: ldr sp, =4096 @ 设置栈指针，以下都是C函数，调用前需要设好栈 bl disable_watch_dog @ 关闭WATCHDOG，否则CPU会不断重启 msr cpsr_c, #0xd2 @ 进入中断模式 ldr sp, =3072 @ 设置中断模式栈指针 msr cpsr_c, #0xd3 @ 进入管理模式 ldr sp, =4096 @ 设置管理模式栈指针， @ 其实复位之后，CPU就处于管理模式， @ 前面的“ldr sp, =4096”完成同样的功能，此句可省略 bl init_led @ 初始化LED的GPIO管脚 bl init_irq @ 调用中断初始化函数，在init.c中 msr cpsr_c, #0x53 @ 设置I-bit=0，开IRQ中断 ldr lr, =halt_loop @ 设置返回地址 ldr pc, =main @ 调用main函数 halt_loop: b halt_loop HandleIRQ: sub lr, lr, #4 @ 计算返回地址 stmdb sp!, { r0-r12,lr } @ 保存使用到的寄存器 @ 注意，此时的sp是中断模式的sp @ 初始值是上面设置的3072 ldr lr, =int_return @ 设置调用ISR即EINT_Handle函数后的返回地址 ldr pc, =EINT_Handle @ 调用中断服务函数，在interrupt.c中 int_return: ldmia sp!, { r0-r12,pc }^ @ 中断返回, ^表示将spsr的值复制到cpsr
int.c文件
/* * init.c: 进行一些初始化 */ #include "s3c24xx.h" /* * LED1,LED2,LED4对应GPF4、GPF5、GPF6 */ #define GPF4_out (1<<(4*2)) #define GPF5_out (1<<(5*2)) #define GPF6_out (1<<(6*2)) #define GPF4_msk (3<<(4*2)) #define GPF5_msk (3<<(5*2)) #define GPF6_msk (3<<(6*2)) /* * S2,S3,S4对应GPF0、GPF2、GPG3 */ #define GPF0_eint (0x2<<(0*2)) #define GPF2_eint (0x2<<(2*2)) #define GPG3_eint (0x2<<(3*2)) #define GPF0_msk (3<<(0*2)) #define GPF2_msk (3<<(2*2)) #define GPG3_msk (3<<(3*2)) /* * 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 } void init_led(void) { // LED1,LED2,LED4对应的3根引脚设为输出 GPFCON &= ~(GPF4_msk | GPF5_msk | GPF6_msk); GPFCON |= GPF4_out | GPF5_out | GPF6_out; } /* * 初始化GPIO引脚为外部中断 * GPIO引脚用作外部中断时，默认为低电平触发、IRQ方式(不用设置INTMOD) */ void init_irq( ) { // S2,S3对应的2根引脚设为中断引脚 EINT0,ENT2 GPFCON &= ~(GPF0_msk | GPF2_msk); GPFCON |= GPF0_eint | GPF2_eint; // S4对应的引脚设为中断引脚EINT11 GPGCON &= ~GPG3_msk; GPGCON |= GPG3_eint; // 对于EINT11，需要在EINTMASK寄存器中使能它 EINTMASK &= ~(1<<11); /*
* 设定优先级： * ARB_SEL0 = 00b, ARB_MODE0 = 0: REQ1 > REQ3，即EINT0 > EINT2 * 仲裁器1、6无需设置 * 最终： * EINT0 > EINT2 > EINT11即K2 > K3 > K4 */ PRIORITY = (PRIORITY & ((~0x01) | (0x3<<7))) | (0x0 << 7) ; // EINT0、EINT2、EINT8_23使能 INTMSK &= (~(1<<0)) & (~(1<<2)) & (~(1<<5)); }
interrupt.c
#include "s3c24xx.h" void EINT_Handle() { unsigned long oft = INTOFFSET; unsigned long val; switch( oft ) { // S2被按下 case 0: { GPFDAT |= (0x7<<4); // 所有LED熄灭 GPFDAT &= ~(1<<4); // LED1点亮 break; } // S3被按下 case 2: { GPFDAT |= (0x7<<4); // 所有LED熄灭 GPFDAT &= ~(1<<5); // LED2点亮 break; } // K4被按下 case 5: { GPFDAT |= (0x7<<4); // 所有LED熄灭 GPFDAT &= ~(1<<6); // LED4点亮 break; } default: break; } //清中断 if( oft == 5 ) EINTPEND = (1<<11); // EINT8_23合用IRQ5 SRCPND = 1<<oft; INTPND = 1<<oft; }
头文件
/* WOTCH DOG register */ #define WTCON (*(volatile unsigned long *)0x53000000) /* SDRAM regisers */ #define MEM_CTL_BASE 0x48000000 #define SDRAM_BASE 0x30000000 /* NAND Flash registers */ #define NFCONF (*(volatile unsigned int *)0x4e000000) #define NFCMD (*(volatile unsigned char *)0x4e000004) #define NFADDR (*(volatile unsigned char *)0x4e000008) #define NFDATA (*(volatile unsigned char *)0x4e00000c) #define NFSTAT (*(volatile unsigned char *)0x4e000010) /*GPIO registers*/ #define GPBCON (*(volatile unsigned long *)0x56000010) #define GPBDAT (*(volatile unsigned long *)0x56000014) #define GPFCON (*(volatile unsigned long *)0x56000050) #define GPFDAT (*(volatile unsigned long *)0x56000054) #define GPFUP (*(volatile unsigned long *)0x56000058) #define GPGCON (*(volatile unsigned long *)0x56000060) #define GPGDAT (*(volatile unsigned long *)0x56000064) #define GPGUP (*(volatile unsigned long *)0x56000068) #define GPHCON (*(volatile unsigned long *)0x56000070) #define GPHDAT (*(volatile unsigned long *)0x56000074) #define GPHUP (*(volatile unsigned long *)0x56000078) /*UART registers*/ #define ULCON0 (*(volatile unsigned long *)0x50000000) #define UCON0 (*(volatile unsigned long *)0x50000004) #define UFCON0 (*(volatile unsigned long *)0x50000008) #define UMCON0 (*(volatile unsigned long *)0x5000000c) #define UTRSTAT0 (*(volatile unsigned long *)0x50000010) #define UTXH0 (*(volatile unsigned char *)0x50000020) #define URXH0 (*(volatile unsigned char *)0x50000024) #define UBRDIV0 (*(volatile unsigned long *)0x50000028) /*interrupt registes*/ #define SRCPND (*(volatile unsigned long *)0x4A000000) #define INTMOD (*(volatile unsigned long *)0x4A000004) #define INTMSK (*(volatile unsigned long *)0x4A000008) #define PRIORITY (*(volatile unsigned long *)0x4A00000c) #define INTPND (*(volatile unsigned long *)0x4A000010) #define INTOFFSET (*(volatile unsigned long *)0x4A000014) #define SUBSRCPND (*(volatile unsigned long *)0x4A000018) #define INTSUBMSK (*(volatile unsigned long *)0x4A00001c) /*external interrupt registers*/ #define EINTMASK (*(volatile unsigned long *)0x560000a4) #define EINTPEND (*(volatile unsigned long *)0x560000a8)
Makefile
objs := head.o init.o interrupt.o main.o
int.bin: $(objs)
arm-linux-ld -Ttext 0x00000000 -o int_elf $^
arm-linux-objcopy -O binary -S int_elf $@
arm-linux-objdump -D -m arm int_elf > int.dis
%.o:%.c
arm-linux-gcc -Wall -O2 -c -o $@ $<
%.o:%.S
arm-linux-gcc -Wall -O2 -c -o $@ $<
clean:
rm -f int.bin int_elf int.dis *.o
main函数是一个while（1）
原文：http://www.cnblogs.com/txiyan/p/6380300.html