mini2440 裸机程序程序心得

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1、写裸机程序心得

硬件初始化：a、关闭看门狗 b、初始化时钟 c、配置sdram,并初始化

软件初始化：a、设置堆栈 SP b、设置返回地址 c、调用函数 d、清理工作

看门狗代码：

void disable_watch_dog(void)
{
WTCON = 0; // 关闭WATCHDOG很简单，往这个寄存器写0即可
}

初始化时钟：

#define S3C2440_MPLL_200MHZ ((0x5c<<12)|(0x01<<4)|(0x02))

#define S3C2440_MPLL_400MHZ ((0x5c<<12)|(0x01<<4)|(0x01))

/*
* 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) = (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

// CLKDIVN= 0x05 //表示FCLK:HCLK:PCLK=1:4:8

    /* 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 */
    }
}

if ((GSTATUS1 == 0x32410000) || (GSTATUS1 == 0x32410002))
    {
        MPLLCON = S3C2410_MPLL_400MHZ; /* 现在，FCLK=400MHz,HCLK=100MHz,PCLK=50MHz */
    }
    else
    {
        MPLLCON = S3C2440_MPLL_400MHZ; /* 现在，FCLK=400MHz,HCLK=100MHz,PCLK=50MHz */
    }

*****************************************************************************************************************************

配置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
}

拷贝代码倒闭SDRAM中

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++;
    }
}

设置堆栈;：

ldr SP ,=4*1024

设置返回地址：

ldr lr , =loop

调用函数：

bl main

注意事项：

ldr pc ,=main与bl main的位置无关码

2、s3cc4xx.h

/* 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)

3、GPIO的初始化

#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

#define GPB5_mask (3<<(5*2))
#define GPB6_mask (3<<(6*2))
#define GPB7_mask (3<<(7*2))
#define GPB8_mask (3<<(8*2))

void init_led(void)
{
       GPBCON &= ~(GPB5_mask|GPB6_mask|GPB7_mask|GPB8_mask);
        GPBCON = GPB5_out | GPB6_out | GPB7_out | GPB8_out ;

}