电子工程师名片——SPI NOR 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 ;
    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=;
    SPI0DAT=FLASH_WRITE_STATUS;
    while(!SPIF);
    SPIF=;

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

    NSSMD0=;//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

否则可能SPI口的OUT输出驱动不了，导致波形都没有。

贴上Flash操作的代码：

#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

];//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=;

    SPI0DAT=FLASH_READ_ID;
    while(!SPIF);
    SPIF=;

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

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

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

    NSSMD0=;
}

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

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

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

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

    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 ;
    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=;
    SPI0DAT=FLASH_WRITE_STATUS;
    while(!SPIF);
    SPIF=;

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

    NSSMD0=;//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 ;
    SPI_WRITE_ENABLE();

    NSSMD0=;

    SPI0DAT=FLASH_SECTOR_ERASE;
    while(!SPIF);
    SPIF=;

    //any address in the sector,but i choose the first address of sector
    SPI0DAT=0x00;            //high address
    while(!SPIF);
    SPIF=;
    SPI0DAT=sectors<<;        //middle address
    while(!SPIF);
    SPIF=;
    SPI0DAT=0x00;            //low address
    while(!SPIF);
    SPIF=;

    NSSMD0=;

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

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

    ;i<;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=;                 //read datas out
        while(!SPIF);
        SPIF=;
        buff[i]=SPI0DAT;
    }
    NSSMD0=;
}

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

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

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

    NSSMD0=;

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