Отправлено dfn 15 марта 2004 г. 16:55 В ответ на: Кто может порекомендовать, чтобы почитать о NAND flash bad block отправлено zerg78 15 марта 2004 г. 11:41

для примера NAND Flash на 32MБайта имеет 2048 блоков по 16кБайт (без учета дополнительной области). Новая флеш имеет гарантированных 2013 хороших блоков. После 100 тыс циклов стирания гарантируются минимум 1004 хороших блока на каждые 128Мбит памяти. Т.е. для 32МБайтной флеш будет 2008 хороших блоков.

Информация о плохом блоке отражается в "Spare Area" - дополнительных 16байтах в каждой странице.

Identifying Invalid Block(s)

Invalid blocks are defined as blocks that contain one or more invalid bits whose reliability is not guaranteed by Samsung. The infor-mation
regarding the invalid block(s) is so called as the invalid block information. Devices with invalid block(s) have the same quality
level as devices with all valid blocks and have the same AC and DC characteristics. An invalid block(s) does not affect the perfor-mance
of valid block(s) because it is isolated from the bit line and the common source line by a select transistor. The system design
must be able to mask out the invalid block(s) via address mapping. The 1st block, which is placed on 00h block address, is guaran-teed
to be a valid block, does not require Error Correction up to 1K Program/Erase cycles.

Invalid Block(s)
All device locations are erased(FFh) except locations where the invalid block(s) information is written prior to shipping. The invalid
block(s) status is defined by the 6th byte(X8 device) or 1st word(X16 device) in the spare area. Samsung makes sure that either the
1st or 2nd page of every invalid block has non-FFh(X8 device) or non-FFFFh(X16 device) data at the column address of 517(X8
device) or 256 and 261(X16 device). Since the invalid block information is also erasable in most cases, it is impossible to recover the
information once it has been erased. Therefore, the system must be able to recognize the invalid block(s) based on the original
invalid block information and create the invalid block table via the following suggested flow chart(Figure 3). Any intentional erasure of
the original invalid block information is prohibited.