专题3-NandFlash变硬盘
第1课-NandFlash原理解析
- 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。
- 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
- 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;
}