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
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
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);
}