FLASH存储器学习笔记

FLASH页块分析

一般flash存储器以页和块为单位，页是最小单位，以多少字节为一页，读也是以页为最小单位读，在一个页内读取某个地址的数据

而一块里面又分为多少页，一般块为最小擦除单元

FLASH的读和写分析

读：

FLASH的读取一般是先发出页地址，再发出行地址，页地址代表在哪个页，行地址代表在页内哪个地址

如果是连续读取的话，只需要发出起始地址即可，后面直接读就可以了，如果是超出了一页要重新发出地址读取写一页

写

一般是先擦除再写，地址发出同上，擦除是以块为单位，并且有的flash还要去除写保护

写基本和读差不多，但是写要先擦除，擦除地址和长度必须是块的整数倍

读FLASH代码

void nand_read(unsigned int addr, unsigned char *buf, unsigned int len)
{
	int i = 0;
	int page = addr / 2048;
	int col  = addr & (2048 - 1);
	
	nand_select(); 

	while (i < len)
	{
		/* 发出00h命令 */
		nand_cmd(00);

		/* 发出地址 */
		/* col addr */
		nand_addr_byte(col & 0xff);
		nand_addr_byte((col>>8) & 0xff);

		/* row/page addr */
		nand_addr_byte(page & 0xff);
		nand_addr_byte((page>>8) & 0xff);
		nand_addr_byte((page>>16) & 0xff);

		/* 发出30h命令 */
		nand_cmd(0x30);

		/* 等待就绪 */
		wait_ready();

		/* 读数据 不能超过一页，不能超过数据长度*/
		for (; (col < 2048) && (i < len); col++)
		{
			buf[i++] = nand_data();			
		}
		if (i == len)
			break;

		col = 0;
		page++;  //超过一页，往下一页读取
	}
	
	nand_deselect(); 	
}

写FLASH代码

nt nand_erase(unsigned int addr, unsigned int len)
{
	int page = addr / 2048;

	if (addr & (0x1FFFF)) //起始地址必须是块的整数倍
	{
		printf("nand_erase err, addr is not block align\n\r");
		return -1;
	}
	
	if (len & (0x1FFFF)) //长度是块的整数倍
	{
		printf("nand_erase err, len is not block align\n\r");
		return -1;
	}
	
	nand_select(); 

	while (1)
	{
		page = addr / 2048;
		
		nand_cmd(0x60);
		
		/* row/page addr */
		nand_addr_byte(page & 0xff);
		nand_addr_byte((page>>8) & 0xff);
		nand_addr_byte((page>>16) & 0xff);

		nand_cmd(0xD0);

		wait_ready();

		len -= (128*1024);
		if (len == 0)
			break;
		addr += (128*1024); //擦除下一块
	}
	
	nand_deselect(); 	
	return 0;
}

void nand_write(unsigned int addr, unsigned char *buf, unsigned int len)
{
	int page = addr / 2048;
	int col  = addr & (2048 - 1);
	int i = 0;

	nand_select(); 

	while (1)
	{
		nand_cmd(0x80);

		/* 发出地址 */
		/* col addr */
		nand_addr_byte(col & 0xff);
		nand_addr_byte((col>>8) & 0xff);
		
		/* row/page addr */
		nand_addr_byte(page & 0xff);
		nand_addr_byte((page>>8) & 0xff);
		nand_addr_byte((page>>16) & 0xff);

		/* 发出数据 */
		for (; (col < 2048) && (i < len); )
		{
			nand_w_data(buf[i++]);
		}
		nand_cmd(0x10);
		wait_ready();

		if (i == len)
			break;
		else
		{
			/* 开始下一个循环page */
			col = 0;
			page++;
		}
		
	}
	
	nand_deselect(); 	
}