unsigned int end   = start_addr + size;

        while(start < end){                             //ÿ¶ÁÒ»Ò³ÐèÒª·¢Ò»´ÎÃüÁî

                write_command(0x00);

                write_address(start);

                write_command(0x30);

                wait_ready();

                while((col<2048) && (start<end)){  //ÔÚÒ»Ò³ÖжÁ£¬ÎÒÓõÄÐͺÅÒ»Ò³´óСΪ2K

                        *des = read_one_data();

                        des++;

                        col++;

                        start++;

                }

                col =0;

        }

        deselect_chip();

}