实验(8)、MPLL和定时器操作
一、编写使用按键中断程序
1、程序功能：启动MPLL，提高系统时钟，初始化存储控制器使SDRAM工作在新的HCLK下，然后将定时器0设置为0.5s产生一次中断，在中断服务程序中改变LED的状态。
2、写程序如下：head.S、init.c、interrupt.c、main.c、s3c24xx.h、makefile
（1）head.S程序如下：
@******************************************************************************
@ File：head.S
@功能：初始化，设置中断模式、系统模式的栈，设置好中断处理函数
@******************************************************************************
.extern main
.text
.global _start
_start:
@******************************************************************************
@中断向量，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
bl clock_init @设置MPLL，改变FCLK、HCLK、PCLK
bl memsetup @设置存储控制器以使用SDRAM
bl copy_steppingstone_to_sdram @复制代码到SDRAM中
ldr pc, =on_sdram @跳到SDRAM中继续执行
on_sdram:
msr cpsr_c, #0xd2 @进入中断模式
ldr sp, =4096 @设置中断模式栈指针
msr cpsr_c, #0xdf @进入系统模式
ldr sp, =0x34000000 @设置系统模式栈指针，
bl init_led @初始化LED的GPIO管脚
bl timer0_init @初始化定时器0
bl init_irq @调用中断初始化函数，在init.c中
msr cpsr_c, #0x5f @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4096
ldr lr, =int_return @设置调用ISR即EINT_Handle函数后的返回地址
ldr pc, =Timer0_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
（2）init.c程序如下：
/*
* 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=200M,HCLK=100M,PCLK=50M*/
}
else
{
MPLLCON = S3C2440_MPLL_200MHZ; /*现在，FCLK=200M,HCLK=100M,PCLK=50M*/
}
}
/*
*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++;
}
}
/*
* LED1-4对应GPB5、GPB6、GPB7、GPB8
*/
#define GPB5_out (1<<(5*2)) // LED1
#define GPB6_out (1<<(6*2)) // LED2
#define GPB7_out (1<<(7*2)) // LED3
#define GPB8_out (1<<(8*2)) // LED4
/*
* K1-K4对应GPF1/EINT1、GPF4/EINT4、GPF2/EINT2、GPF0/EINT0；
*/
#define GPF1_eint (2<<(1*2)) // K1,EINT1
#define GPF4_eint (2<<(4*2)) // K2,EINT4
#define GPF2_eint (2<<(2*2)) // K3,EINT2
#define GPF0_eint (2<<(0*2)) // K4,EINT0
void init_led(void)
{
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=50MHz/(99+1)/(16)=31250Hz
*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 = 15625; // 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));
}
（3）interrupt.c程序如下：
#include "s3c24xx.h"
void Timer0_Handle(void)
{
/*
*每次中断令4个LED改变状态
*/
if(INTOFFSET == 10)
{
GPBDAT ^= (0xf << 5);
}
//清中断
SRCPND = 1 << INTOFFSET;
INTPND = INTPND;
}
（4）main.c程序如下：
int main()
{
while(1);
return 0;
}
（5）s3c24xx.h程序如下：
/* 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)
/*clock registers*/
#define LOCKTIME (*(volatile unsigned long *)0x4c000000)
#define MPLLCON (*(volatile unsigned long *)0x4c000004)
#define UPLLCON (*(volatile unsigned long *)0x4c000008)
#define CLKCON (*(volatile unsigned long *)0x4c00000c)
#define CLKSLOW (*(volatile unsigned long *)0x4c000010)
#define CLKDIVN (*(volatile unsigned long *)0x4c000014)
/*PWM & Timer registers*/
#define TCFG0 (*(volatile unsigned long *)0x51000000)
#define TCFG1 (*(volatile unsigned long *)0x51000004)
#define TCON (*(volatile unsigned long *)0x51000008)
#define TCNTB0 (*(volatile unsigned long *)0x5100000c)
#define TCMPB0 (*(volatile unsigned long *)0x51000010)
#define TCNTO0 (*(volatile unsigned long *)0x51000014)
#define GSTATUS1 (*(volatile unsigned long *)0x560000B0)
（6）Makefile程序如下：
objs := head.o init.o interrupt.o main.o
timer.bin: $(objs)
arm-linux-ld -Ttimer.lds -o timer_elf $^
arm-linux-objcopy -O binary -S timer_elf $@
arm-linux-objdump -D -m arm timer_elf > timer.dis
%.o:%.c
arm-linux-gcc -nostdlib –Wall -c -o $@ $<
%.o:%.S
arm-linux-gcc -nostdlib -Wall -c -o $@ $<
clean:
rm -f timer.bin timer_elf timer.dis *.o
Q&A:
（1）请查阅教材和网络，说明本实验makefile中$^指什么文件？$@指什么文件，$<指什么文件？再对比实验四的makefile
（2）根据第一个问题，将makefile重新编写后编译