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 alignnr");return -1;}if (len & (0x1FFFF)) //长度是块的整数倍{printf("nand_erase err, len is not block alignnr");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(); }