K9K1G08U0M-YCB0, K9K1G08U0M-YIB0

FLASH MEMORY

10

NAND Flash Technical Notes

Identifying Invalid Block(s)

Invalid Block(s)

Invalid blocks are defined as blocks that contain one or more invalid bits whose reliability is not guaranteed by Samsung. The i nfor-

mation regarding the invalid block(s) is so called as the invalid block information. Devices with invalid block(s) have the same quality

level or 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 of the NAND Flash, however, is fully guaranteed to

be a valid block. The 1st block, which is placed on 00h block address, is fully guaranteed to be a valid block, does not require Error

Correction.

All device locations are erased(FFh) except locations where the invalid block(s) information is written prior to shipping. The i nvalid

block(s) status is defined by the 6th byte in the spare area. Samsung makes sure that either the 1st or 2nd page of every invali d

block has non-FFh data at the column address of 517. Since the invalid block information is also erasable in most cases, it is impos-

sible 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 4). Any inten-

tional erasure of the original invalid block information is prohibited.

*

Check "FFh" at the column address 517

Figure 4. Flow chart to create invalid block table.

Start

Set Block Address = 0

Check "FFh" ?

Increment Block Address

Last Block ?

End

No

Yes

Yes

Create (or update)

No

Invalid Block(s) Table

of the 1st and 2nd page in the block