电子工程师名片——SPI Flash

使用了MX25L512的SPI接口的Flash

电路连接图：

总的大小512kb，即64kB，sector的大小为256 Bytes，block的大小为4k Bytes

调试时出现的问题：

1、Flash只能读数据，不能写数据

根源在于Flash的软件写保护没有去掉，这样，写、擦除，甚至写状态寄存器都不能执行。

1）Hardware Protection

Hardware Protection Mode(HPM):by using WP# going low to protect the BP0-BP1 bits and SRWD bit from data change

因为WP#是高电平，所以没有硬件保护，再来看软件保护。

2）Software Protection

Software Protection Mode(SPM):by using BP0-BP1 bits to set the part of flash protected from data change

通过下面几幅图可知，在WP#高电平情况下write status register可以改变SRWD、BP0、BP1的值为0，从而去掉软件写保护。

3）代码实现去除保护

//在所有需要修改的操作之前必须去除软件保护BP0,BP1
//FLASH的状态寄存器
//bit7    bit6  bit5  bit4  bit3  bit2  bit1      bit0
//SRWD    0   0     0   BP1   BP0   WEL       WIP
// 1=status write disable             1=write enable  1=write in process
#define MASK_CLEAR_BPX 0x73 //掩码，设置使能写状态寄存器，清除BP1、BP0
void SPI_WRITE_STATUS()  //主要是清除保护，可以写数据
{
  unsigned char status=0; 
  SPI_WRITE_ENABLE(); //设置状态器WEL位为1，在进行写状态寄存器之前必须写使能
  status=SPI_READ_STATUS();
  
  NSSMD0=0;
  SPI0DAT=FLASH_WRITE_STATUS;
  while(!SPIF);
  SPIF=0;

  SPI0DAT=status&MASK_CLEAR_BPX;
  while(!SPIF);
  SPIF=0;

  NSSMD0=1;//cs must go high at the byte boundary,otherwise instruction will be reject and not executed

  do    //query until WIP convert from 1 to 0 when write status register cycle is finished
  {
    status=SPI_READ_STATUS();
    status=status&0x01;
  }while(status);
}

2、sector大小为256 Bytes，但是连续写256 Bytes，只有最后的32 Bytes写进去了

在测试MX25L512的扇区的时候，老是遇到一个问题，写入256个字节，但是读出的是最后32个Bytes，前面的总是0xFF，于是就怀疑是不是扇区

的大小没有datasheet所说的那么大呢？最后测试发现扇区的大小只有32Bytes，如果连续写入的字节数大于32 Bytes，就会把除最后32 Bytes之外

的数据丢弃，只写最后的32 Bytes。仔细翻看datasheet，发现MX25L512MC-12G的扇区为256 Bytes，而MX25L512IE的扇区只有32Bytes原来具体

芯片规格和元件后缀名也有关系。

说明：sector是读写数据的最小单元，block是擦除的最小单元。（有时候sector概念类似于page，要看具体的芯片）

扇区被擦除后内部的数据变为0xFF。

3、SPI接口波形不对

虽然C8051F320已经交叉配置为串口和SPI接口，但是实际情况是还是要在输出的管脚PushPull，

P0MDOUT=0x1D;//0001 1101

#ifndef _SPI_CMD_H_
#define _SPI_CMD_H_

#include"misc.h"

//MX25L512的flash说明///
//page:256byte
//sector:4kbyte
//注意MX25L512MC-12G page为256 bytes
//MX25L512IE.. page为32 bytes
///

#define FLASH_READ_ID     0x9F  //读设备ID
#define FLASH_WRITE_ENABLE  0x06  //写使能
#define FLASH_WRITE_DISABLE   0x04  //写禁止
#define FLASH_READ_STATUS     0x05  //读状态寄存器
#define FLASH_WRITE_STATUS  0x01  //写状态寄存器
#define FLASH_READ_DATA   0x03  //读数据
#define FLASH_WRITE_DATA    0x02  //写数据
#define FLASH_SECTOR_ERASE  0x20  //擦除一个扇区

extern unsigned char xdata buff[256];//缓冲区全局变量,可以保存一个page的256字节
//在头文件中只是申明一下，不能定义，定义变量要在相应的C文件中定义
//以上不然会报错:multiple public definitions

void SPI_READ_ID();
void SPI_WRITE_ENABLE();
void SPI_WRITE_DISABLE();
unsigned char SPI_READ_STATUS();
void SPI_WRITE_STATUS();
void SPI_SECTOR_ERASE(unsigned char sectors);
void SPI_READ_Page(unsigned char sectors,unsigned char pages);
void SPI_WRITE_Page(unsigned char *str,unsigned char sectors,unsigned char pages);
void FillDBR();

#endif

#include"SPI_CMD.h"

//#define SPI0INT(x) {SPI0DAT=x;while(!SPIF);SPIF=0;}
//可以用这个定义来取代以下一大段的代码
//SPI0DAT=FLASH_READ_ID;
//while(!SPIF);          ----->SPI0DAT=FLASH_READ_ID;
//SPIF=0;
void SPI_READ_ID()
{
  NSSMD0=0;
  
  SPI0DAT=FLASH_READ_ID;
  while(!SPIF);
  SPIF=0;

  SPI0DAT=0;  //dummy write to output serial clock
  while(!SPIF); //wait for value to be read
  SPIF=0;
  sendChar(SPI0DAT);
  
  SPI0DAT=0;
  while(!SPIF);
  SPIF=0;
  sendChar(SPI0DAT);  

  SPI0DAT=0;
  while(!SPIF);
  SPIF=0;
  sendChar(SPI0DAT);

  NSSMD0=1;
}

void SPI_WRITE_ENABLE()
{
  NSSMD0=0;
  SPI0DAT=FLASH_WRITE_ENABLE;
  while(!SPIF);
  SPIF=0;
  NSSMD0=1; 
}

void SPI_WRITE_DISABLE()
{
  NSSMD0=0;
  SPI0DAT=FLASH_WRITE_DISABLE;
  while(!SPIF);
  SPIF=0;
  NSSMD0=1; 
}

unsigned char SPI_READ_STATUS()
{
  NSSMD0=0;
  SPI0DAT=FLASH_READ_STATUS;//可以将类似的这种形式做成一个宏定义
  while(!SPIF);
  SPIF=0;

  SPI0DAT=0;
  while(!SPIF);
  SPIF=0;
  NSSMD0=1;

  return SPI0DAT;
}

//在所有需要修改的操作之前必须去除软件保护BP0,BP1
//FLASH的状态寄存器
//bit7    bit6  bit5  bit4  bit3  bit2  bit1      bit0
//SRWD    0   0     0   BP1   BP0   WEL       WIP
// 1=status write disable             1=write enable  1=write in process
#define MASK_CLEAR_BPX 0x73 //掩码，设置使能写状态寄存器，清除BP1、BP0
void SPI_WRITE_STATUS()  //主要是清除保护，可以写数据
{
  unsigned char status=0; 
  SPI_WRITE_ENABLE(); //设置状态器WEL位为1，在进行写状态寄存器之前必须写使能
  status=SPI_READ_STATUS();
  
  NSSMD0=0;
  SPI0DAT=FLASH_WRITE_STATUS;
  while(!SPIF);
  SPIF=0;

  SPI0DAT=status&MASK_CLEAR_BPX;
  while(!SPIF);
  SPIF=0;

  NSSMD0=1;//cs must go high at the byte boundary,otherwise instruction will be reject and not executed

  do    //query until WIP convert from 1 to 0 when write status register cycle is finished
  {
    status=SPI_READ_STATUS();
    status=status&0x01;
  }while(status);
}

void SPI_SECTOR_ERASE(unsigned char sectors)
{
  unsigned char status=0;
  SPI_WRITE_ENABLE();
    
  NSSMD0=0;
  
  SPI0DAT=FLASH_SECTOR_ERASE;
  while(!SPIF);
  SPIF=0;
  
  //any address in the sector,but i choose the first address of sector
  SPI0DAT=0x00;     //high address 
  while(!SPIF);
  SPIF=0;
  SPI0DAT=sectors<<4;   //middle address
  while(!SPIF);
  SPIF=0;
  SPI0DAT=0x00;     //low address
  while(!SPIF);
  SPIF=0;

  NSSMD0=1;

  do    //query until WIP convert from 1 to 0 when write status register cycle is finished
  {
    status=SPI_READ_STATUS();
    status=status&0x01;
  }while(status);
}

unsigned char xdata buff[256];
//读一页256 bytes
void SPI_READ_Page(unsigned char sectors,unsigned char pages)
{
  unsigned int i=0;
  NSSMD0=0;
  SPI0DAT=FLASH_READ_DATA; //command
  while(!SPIF);
  SPIF=0;

  SPI0DAT=0x00;      //read address
  while(!SPIF);
  SPIF=0;
  SPI0DAT=(sectors<<4) + pages;
  while(!SPIF);
  SPIF=0;
  SPI0DAT=0x00;
  while(!SPIF);
  SPIF=0;

  for(i=0;i<256;i++)     //read a page 256 bytes
  {           //实测每页的数据只有32byte，所以一次连续写32byte
    SPI0DAT=0;         //read datas out
    while(!SPIF);
    SPIF=0;
    buff[i]=SPI0DAT;
  }
  NSSMD0=1;
}

//写一页256 bytes
void SPI_WRITE_Page(unsigned char *str,unsigned char sectors,unsigned char pages)
{
  unsigned int i=0;
  unsigned char status=0;
  SPI_WRITE_ENABLE();   //在改变数据之前都要进行写使能操作
  NSSMD0=0;
  SPI0DAT=FLASH_WRITE_DATA; //write command
  while(!SPIF);
  SPIF=0;

  SPI0DAT=0x00;      //write address
  while(!SPIF);       //最高地址默认为0x00，所以不用传他的参数
  SPIF=0;
  SPI0DAT=(sectors<<4) + pages;
  while(!SPIF);
  SPIF=0;
  SPI0DAT=0x00;
  while(!SPIF);
  SPIF=0;

  for(i=0;i<256;i++)   //write a page 256 bytes
  {
    SPI0DAT=str[i]; //write data in
    while(!SPIF);
    SPIF=0;
  }
  
  NSSMD0=1;

  do    //query until WIP convert from 1 to 0 when write cycle is finished
  {
    status=SPI_READ_STATUS();
    status=status&0x01;
  }while(status);
}

电子工程师名片——SPI Flash

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