K9F2808U0B-YCB0,YIB0
K9F2808Q0B-DCB0,DIB0
K9F2808U0B-VCB0,VIB0 K9F2808U0B-DCB0,DIB0
FLASH MEMORY
NAND Flash Technical Notes
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 invalid block(s) is so called as the invalid block information. Devices ,regardless of having invalid block(s), have the
same quality level because all valid blocks have same AC and DC characteristics. An invalid block(s) does not affect the perfor-
mance of valid block(s) because it’ s bit line and common source line is isolated by a select transistor. The system design must be
able to mask out invalid block(s) via address mapping. The 1st block, which is placed on 00h block address, is fully guaranteed to be
a valid block, does not require Error Correction.
Identifying 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 in the spare area. Samsung makes sure that either 1st or 2nd page of every invalid block
has non-FFh data at the column address of 517. Since invalid block information is also erasable in most cases, it is impossible to
recover the information once it was erased. Therefore, system must be able to recognize the invalid block(s) based on the original
invalid block information and create invalid block table via the following suggested flow chart(Figure 3). Any intentional erasure of the
original invalid block information is prohibited.
Start
Set Block Address = 0
Increment Block Address
Check "FFh" at the column address 517
*
of the 1st and 2nd page in the block
No
Create (or update)
Invalid Block(s) Table
Check "FFh" ?
Yes
No
Last Block ?
Yes
End
Figure 3. Flow chart to create invalid block table.
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SAMSUNG [ SAMSUNG ]
