专题3-NandFlash变硬盘

第1课-NandFlash原理解析

1. 角色分析

在电脑中有硬盘，它是用来存储文件的。嵌入式系统是防电脑的系统，在嵌入式系统中，NandFlash就相当于硬盘的存在。

1. NandFlash的分类

2.1 根据物理结构上的区别，NandFlash主要分为如下两类：

l  SLC（Single Level Cell）：单层式存储

l  MLC（Muti Level Cell）：多层式存储

SLC在存储格上只存一位数据，而MLC则存放两位数据

2.2 MLC对比SLC

价格：由于MLC采用了更高密度的存储方式，因此同容量的MLC价格上远低于SLC

访问速度：SLC的访问速度一般要比MLC快3倍以上

使用寿命：SLC能进行10万次的擦写，MLC能进行1万次

功耗：MLC功耗比SLC高15%左右

1. 访问方式

（1）       对比内存与NandFlash的编址区别

CPU内部有NandFlash控制，负责NandFlash与CPU之间的通信，通过地址、命令和数据三个寄存器来完成这一系列的通信。

（2）       NandFlash地址构成

一块NandFlash划分成多个Block，一个Block划分成多个page，一个page划分成两个部分。

（3）       信号引脚

CLE(Command Latch Enable): 命令锁存允许

ALE(Address Lactch Enable): 地址锁存允许

CE:芯片选择

RE:读允许

WE:写允许

WE:写允许

WP:在写或擦除期间，提供写保护

R/B:读/忙

第2课-NandFlash驱动设计~读

#define NFCONF (*(volatile unsigned long*)0x4E000000)

#define NFCONT (*(volatile unsigned long*)0x4E000004)

#define NFSTAT (*(volatile unsigned char*)0x4E000020)

#define NFCMD  (*(volatile unsigned char*)0x4E000008)

#define NFADDR (*(volatile unsigned char*)0x4E00000C)

#define NFDATA (*(volatile unsigned char*)0x4E000010)

#define TACLS 1

#define TWRPH0 2

#define TWRPH1 1

void select_chip()

{

NFCONT &= ~(1<<1);

}

void deselect_chip()

{

NFCONT |= (1<<1);

}

void clear_RnB()

{

NFSTAT |= (1<<2);

}

void send_cmd(unsigned cmd)

{

NFCMD = cmd;

}

void send_addr(unsigned addr)

{

NFADDR = addr;

}

void wait_RnB()

{

while (!(NFSTAT&(1<<2)))

{

;

}

}

void nand_reset()

{

//选中flash

select_chip();

//清除RnB

clear_RnB();

//发送0xff命令

send_cmd(0xff);

//等待RnB

wait_RnB();

//取消选中flash

deselect_chip();

}

void nand_init()

{

//初始化NFCONF

NFCONF = (TACLS<<12) | (TWRPH0<<8) | (TWRPH1<<4);

//初始化NFCONT

NFCONT = (1<<0) | (1<<1);

//复位

nand_reset();

}

void NF_PageRead(unsigned long addr,unsigned char* buff)

{

int i;

//选中nandflash芯片

select_chip();

//清除RnB

clear_RnB();

//发送命令0x00

send_cmd(0x00);

//发送列地址

send_addr(0x00);

send_addr(0x00);

//发送行地址

send_addr(addr&0xff);

send_addr((addr>>8)&0xff);

send_addr((addr>>16)&0xff);

//发送命令0x30

send_cmd(0x30);

//等待RnB

wait_RnB();

//读取数据

for(i=0;i<2048;i++)

{

buff[i] = NFDATA;

}

//取消选中nandflash芯片

deselect_chip();

}

void nand_to_ram(unsigned long start_addr, unsigned char* sdram_addr, int size)

{

int i;

for( i=(start_addr >>11); size>0;)

{

NF_PageRead(i,sdram_addr);

size -= 2048;

sdram_addr += 2048;

i++;

}

}

第3课-NandFlash驱动设计~写

#define NFCONF (*(volatile unsigned long*)0x4E000000)

#define NFCONT (*(volatile unsigned long*)0x4E000004)

#define NFSTAT (*(volatile unsigned char*)0x4E000020)

#define NFCMD  (*(volatile unsigned char*)0x4E000008)

#define NFADDR (*(volatile unsigned char*)0x4E00000C)

#define NFDATA (*(volatile unsigned char*)0x4E000010)

#define TACLS 1

#define TWRPH0 2

#define TWRPH1 1

void select_chip()

{

NFCONT &= ~(1<<1);

}

void deselect_chip()

{

NFCONT |= (1<<1);

}

void clear_RnB()

{

NFSTAT |= (1<<2);

}

void send_cmd(unsigned cmd)

{

NFCMD = cmd;

}

void send_addr(unsigned addr)

{

NFADDR = addr;

}

void wait_RnB()

{

while (!(NFSTAT&(1<<2)))

{

;

}

}

void nand_reset()

{

//选中flash

select_chip();

//清除RnB

clear_RnB();

//发送0xff命令

send_cmd(0xff);

//等待RnB

wait_RnB();

//取消选中flash

deselect_chip();

}

void nand_init()

{

//初始化NFCONF

NFCONF = (TACLS<<12) | (TWRPH0<<8) | (TWRPH1<<4);

//初始化NFCONT

NFCONT = (1<<0) | (1<<1);

//复位

nand_reset();

}

void NF_PageRead(unsigned long addr,unsigned char* buff)

{

int i;

//选中nandflash芯片

select_chip();

//清除RnB

clear_RnB();

//发送命令0x00

send_cmd(0x00);

//发送列地址

send_addr(0x00);

send_addr(0x00);

//发送行地址

send_addr(addr&0xff);

send_addr((addr>>8)&0xff);

send_addr((addr>>16)&0xff);

//发送命令0x30

send_cmd(0x30);

//等待RnB

wait_RnB();

//读取数据

for(i=0;i<2048;i++)

{

buff[i] = NFDATA;

}

//取消选中nandflash芯片

deselect_chip();

}

void nand_to_ram(unsigned long start_addr, unsigned char* sdram_addr, int size)

{

int i;

for( i=(start_addr >>11); size>0;)

{

NF_PageRead(i,sdram_addr);

size -= 2048;

sdram_addr += 2048;

i++;

}

}

int NF_WritePage(unsigned long addr, unsigned char* buff)

{

int ret;

int i;

//选中flash芯片

select_chip();

//清除RnB

clear_RnB();

//发送命令0x80

send_cmd(0x80);

//发送列地址

send_addr(0x00);

send_addr(0x00);

//发送行地址

send_addr(addr&0xff);

send_addr((addr>>8)&0xff);

send_addr((addr>>16)&0xff);

//写入数据

for(i=0;i<2048;i++)

{

NFDATA = buff[i];

}

//发送命令0x10

send_cmd(0x10);

//等待RnB

wait_RnB();

//发送命令0x70

send_cmd(0x70);

//读取写入结果

ret = NFDATA;

//取消选中flash芯片

deselect_chip();

return ret;

}