LCD实验学习笔记:NAND FLASH

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s3c2440 CPU内置NAND FLASH控制器。相关寄存大器起始地址为0x4e000000。

通过设置NFCONF寄存器,设置NAND FLASH 时序。

通过设置NFCONT寄存器,使能NAND FLASH、初始化ECC等。

代码:


 

#define GSTATUS1 (*(volatile unsigned int *)0x560000B0) //读此寄存器可以知道CPU芯片型号
#define BUSY 1

#define NAND_SECTOR_SIZE_LP 2048 //大页每页2048字节
#define NAND_BLOCK_MASK_LP (NAND_SECTOR_SIZE_LP - 1) //大页掩码???

typedef unsigned int S3C24X0_REG32;

//s3c2440 NAND FLASH相关寄存器
typedef struct {
  S3C24X0_REG32 NFCONF;
  S3C24X0_REG32 NFCONT;
  S3C24X0_REG32 NFCMD;
  S3C24X0_REG32 NFADDR;
  S3C24X0_REG32 NFDATA;
  S3C24X0_REG32 NFMECCD0;
  S3C24X0_REG32 NFMECCD1;
  S3C24X0_REG32 NFSECCD;
  S3C24X0_REG32 NFSTAT;
  S3C24X0_REG32 NFESTAT0;
  S3C24X0_REG32 NFESTAT1;
  S3C24X0_REG32 NFMECC0;
  S3C24X0_REG32 NFMECC1;
  S3C24X0_REG32 NFSECC;
  S3C24X0_REG32 NFSBLK;
  S3C24X0_REG32 NFEBLK;
} S3C2440_NAND;

static S3C2440_NAND * s3c2440nand = (S3C2440_NAND *)0x4e000000;//s3c2440 Nand flash 相关寄存器起始地址

//供外部调用的函数声明
void nand_init(void); //初始化
void nand_read(unsigned char *buf, unsigned long start_addr, int size);//读取数据到缓冲区

/* S3C2440的NAND Flash处理函数 */
static void s3c2440_nand_reset(void);
static void s3c2440_wait_idle(void);
static void s3c2440_nand_select_chip(void);
static void s3c2440_nand_deselect_chip(void);
static void s3c2440_write_cmd(int cmd);
static void s3c2440_write_addr_lp(unsigned int addr);
static unsigned char s3c2440_read_data(void);

//复位
static void s3c2440_nand_reset(void)
{
  s3c2440_nand_select_chip();//选片选
  s3c2440_write_cmd(0xff); //复位命令
  s3c2440_wait_idle(); //等待就绪
  s3c2440_nand_deselect_chip(); //取消片选
}

//等待就绪信号
static void s3c2440_wait_idle(void)
{
  int i;
  volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFSTAT;
  //最后一位为1表示忙,忙就一直等
  while (!(*p & BUSY))
  for (i = 0; i < 10; i++);
}

//片选
static void s3c2440_nand_select_chip()
{
  s3c2440nand->NFCONT &= ~(1 << 1); //NFCONT寄存器[1]位Reg_nCE置0
  int i ;
  for (i = 0; i < 10; i++); //等待片选?
}


//取消片选
static void s3c2440_nand_deselect_chip()
{
  s3c2440nand->NFCONT |=(1<<1); //NFCONT寄存器[1]位Reg_nCE置1
}

//发送命令
static void s3c2440_write_cmd(int cmd)
{
  volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFCMD; //p指向NFCMD寄存器
  *p = cmd; //命令写入命令寄存器
}

//发送地址
static void s3c2440_write_addr_lp(unsigned int addr)
{
  int i;
  volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFADDR;
  int col, page;
  col = addr & NAND_BLOCK_MASK_LP; //得到页内地址。 每页2K,页内地址为bit[0-10]
  page = addr / NAND_SECTOR_SIZE_LP; //得到页号。256M为2的28次方,地址总位数为27,即bit[11-27]为页号,共17位
  *p = col & 0xff; //地址后8位 ,A0-A7;
  for (i = 0; i < 10; i++);
  *p = (col >> 8) & 0x0f; //A8-A10
  for (i = 0; i < 10; i++);
  *p = page & 0xff; //页号后后位 A11-A18
  for (i = 0; i < 10; i++);
  *p = (page >> 8) & 0xff;//A19-A26
  for (i = 0; i < 10; i++);
  *p = (page >> 16) & 0x1; //A27
  for (i = 0; i < 10; i++);}

//读数据
static unsigned char s3c2440_read_data(void)
{
  volatile unsigned char *p = (volatile unsigned char *)&s3c2440nand->NFDATA;
  return *p;
}


//初始化Nand Flash
void nand_init(void)
{
  //设置时序
  //这里假设cpu频率100MHz,即一个时钟周期为10ns
  #define TACLS 0
  #define TWRPH0 3 //nand flash手册 twp最低要求12ns,即2个时钟周期以上,所以这里可以取1的,3可以保证400MHz时可用
  #define TWRPH1 0 //nand flash手册 tCLH最低要求5ns,取值0要求CPU频200Mhz以下
  s3c2440nand->NFCONF = (TACLS << 12) | (TWRPH0 << 8) | (TWRPH1 << 4);
  //使能Nand Flash,禁止片选,初始化ECC
  s3c2440nand->NFCONT = (1 << 4) | (1 << 1) | (1 << 0);
  s3c2440_nand_reset(); //复位
}

//读数据
void nand_read(unsigned char *buf, unsigned long start_addr, int size)
{
  //Nand Flash的读取单位最小是page,长度必须是page的整数倍。所以必须对齐
  if ((start_addr & NAND_BLOCK_MASK_LP)||(size & NAND_BLOCK_MASK_LP))
  {
    return;
  }
  s3c2440_nand_select_chip();//发出片选信号

  int i, j;
  for (i = start_addr; i < (start_addr+size);)
  {
    s3c2440_write_cmd(0); //发出READ0命令
    s3c2440_write_addr_lp(i);
    s3c2440_write_cmd(0x30);
    s3c2440_wait_idle();
    //读取页数据
    for ( j = 0; j <NAND_SECTOR_SIZE_LP;j++,i++)
    {
      *buf = s3c2440_read_data();
      buf++;
    }

  }

  s3c2440_nand_deselect_chip();//取消片选
}


 

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