嵌入式Memo 16 读NAND FLASH On May 6.2013

      本实验使用KF92G08U0B芯片。每页2k空间，总共256M。
    主要问题在写地址上：实验中将main函数在内的2k复制到0x30000000之后，nand每页2k空间.一页分成主要的字段(2 k)和备用字段(64字节)两部分
而我们只使用2 k,所以只用它的低11(A0~A11，12)位。因为页面地址总是2k字节对齐的,所以它的低11总是零。详细参照：
http://blog.chinaunix.net/uid-26310563-id-3142134.html和
。
     代码：
nand.c:
#define NAND_SECTOR_SIZE    2048
#define NAND_BLOCK_MASK     (NAND_SECTOR_SIZE -1)
#define BUSY            1
typedef unsigned int REG32;
typedef struct {
    REG32   NFCONF;
    REG32   NFCONT;
    REG32   NFCMD;
    REG32   NFADDR;
    REG32   NFDATA;
    REG32   NFMECCD0;//not use
    REG32   NFMECCD1;//not use
    REG32   NFSECCD; //not use
    REG32   NFSTAT;
    REG32   NFESTAT0;//not use
    REG32   NFESTAT1;//not use
    REG32   NFMECC0; //not use
    REG32   NFMECC1; //not use
    REG32   NFSECC;  //not use
    REG32   NFSBLK;  //not use 
    REG32   NFEBLK;  //not use
} NAND;
 
static NAND * nand = (NAND *)0x4e000000;
void nand_init(void);
void nand_read(unsigned char *buf, unsigned long start_addr, int size);
static void nand_reset(void);
static void wait_idle(void);
static void nand_select_chip(void);
static void nand_deselect_chip(void);
static void write_cmd(int cmd);
static void write_addr(unsigned int addr);
static unsigned char read_data(void);

static void nand_reset(void)
{
    nand_select_chip();
    write_cmd(0xff);  
    wait_idle();
    nand_deselect_chip();
}
static void wait_idle(void)
{
    int i;
    volatile unsigned char *p = (volatile unsigned char *)&nand->NFSTAT;
    while(!(*p & BUSY))
        for(i=0; i<10; i++);
}
static void nand_select_chip(void)
{
    int i;
    nand->NFCONT &= ~(1<<1);
    for(i=0; i<10; i++);    
}
static void nand_deselect_chip(void)
{
    nand->NFCONT |= (1<<1);
}

static void write_cmd(int cmd)
{
    volatile unsigned char *p = (volatile unsigned char *)&nand->NFCMD;
    *p = cmd;
}

 static void write_addr(unsigned int addr)
{
    int i;
    int col,page;
    addr = addr >> 11;
    col = addr & NAND_BLOCK_MASK;
    page = addr / NAND_SECTOR_SIZE;   
    volatile unsigned char *p = (volatile unsigned char *)&nand->NFADDR;   
   //two ways reach the result
    // the  first method
   // *p = col & 0xff;
   // for(i=0; i<10; i++);
   // *p = (col >> 8) & 0x1f;
   // for(i=0; i<10; i++);
   // *p = page & 0xff;
   // for(i=0; i<10; i++);
   // *p = (page >> 8) & 0xff;
   // for(i=0; i<10; i++);
   // *p = (page >> 16) & 0x03;
   // for(i=0; i<10; i++);
    //the second method
   //firstly:one Page is divided into the Main Field (2 k) 
   //and Spare Field (64 byte) two parts 
   //and we only use the 2k,so it's low 11(not 12)fulfil.
   //Because the page address is always 2048 bytes aligned,
   // so its low 11 is always zero
      *p = 0;
      for(i=0; i<10; i++);
      *p = 0;
      for(i=0; i<10; i++);
      *p = addr & 0xff;
      for(i=0; i<10; i++);
      *p = (addr >> 8) & 0xff;
      for(i=0; i<10; i++);
      *p = (addr >> 16) & 0xff;
      for(i=0; i<10; i++);
}

static unsigned char read_data(void)
{
    volatile unsigned char *p = (volatile unsigned char *)&nand->NFDATA;
    return *p;
}

void nand_init(void)
{
#define TACLS   0
#define TWRPH0  3
#define TWRPH1  0
    nand->NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
    nand->NFCONT = (1<<4)|(1<<1)|(1<<0);
    nand_reset();
}

void nand_read(unsigned char *buf, unsigned long start_addr, int size)
{
    int i, j;
    if ((start_addr & NAND_BLOCK_MASK) || (size & NAND_BLOCK_MASK)) {
        return ;  
    }
    nand_select_chip();
    for(i=start_addr; i < (start_addr + size);) {
      write_cmd(0);
      write_addr(i);
      write_cmd(0x30);
      wait_idle();
      for(j=0; j < NAND_SECTOR_SIZE; j++, i++) {   
          *buf = read_data();
          buf++;
      }
    }
    nand_deselect_chip();
    return ;
}
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