km29u128t Samsung Semiconductor, Inc., km29u128t Datasheet - Page 9

• Manufacturer Part Number: km29u128t
• Description: 16m X 8 Bit Nand Flash Memory
• Manufacturer: Samsung Semiconductor, Inc.

KM29U128T, KM29U128IT
Invalid Block(s)
NAND Flash Technical Notes
Invalid blocks are defined as blocks that contain one or more invalid bits whose reliability is not guaranteed by Samsung. Typically,
an invalid block will contain a single bad bit. The information regarding the invalid block(s) is so called as the invalid block informa-
tion.
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 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.
Identifying Invalid Block(s)
All device locations are erased(FFh) except locations where the invalid block information is written prior to shipping.
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 era-
sure of the original invalid block information is prohibited.
Increment Block Address
The invalid block information is written to the 1st or the 2nd page of the invalid block(s) with 00h data.
Invalid Block(s) Table
Create (or update)
Figure 1. Flow chart to create invalid block table.
No
No
Set Block Address = 0
Check "FFH" ?
9
Last Block ?
Start
End
Yes
Yes
*
Check "FFH" on the 1st and 2nd page
FLASH MEMORY
Devices with invalid
Since the