K9F4008W0A- Datasheet, PDF (9/24 Pages) Samsung semiconductor – 512K x 8 bit NAND Flash Memory

K9F4008W0A-TCB0, K9F4008W0A-TIB0
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 informa-
tion regarding the invalid block(s) is called as the invalid block information. The invalid block information is written to the 1st or the 2nd
page of the invalid block(s) with 00h data. 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 performance of valid block(s) because it is iso-
lated 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 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 information is written prior to shipping. 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 1). Any intentional erasure of the original invalid block information is prohibited.
Start
Set Block Address = 0
Increment Block Address
Create (or update)
No
Invalid Block(s) Table
* ^{Check "FFh" on the 1st and 2nd page}
Check "FFh" ?
Yes
No
Last Block ?
Yes
End
Figure 1. Flow chart to create invalid block table.
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