k9f4008w0a Samsung Semiconductor, Inc., k9f4008w0a Datasheet - Page 10

• Manufacturer Part Number: k9f4008w0a
• Description: 512k X 8 Bit Nand Flash Memory
• Manufacturer: Samsung Semiconductor, Inc.

K9F4008W0A Technical Notes(Continued)
Error in program or erase operation
Over its life time, the additional invalid blocks may develop with NAND Flash memory. Refer to the qualification report for the actual
data.The following possible failure modes should be considered to implement a highly reliable system. In the case of status read fail-
ure after erase or program, block replacement should be done. Because program status fail during a page program does not affect
the data of the other pages in the same block, block replacement can be executed with a page-sized buffer by finding an erased
empty block and reprogramming the current target data and copying the rest of the replaced block. To improve the efficiency of mem-
ory space, it is recommended that the read or verification failure due to single bit error be reclaimed by ECC without any block
replacement. The said additional block failure rate does not include those reclaimed blocks.
K9F4008W0A-TCB0, K9F4008W0A-TIB0
* Step1
When an error happens in the nth page of the Block ’A’ during erase or program operation.
* Step2
Copy the nth page data of the Block ’A’ in the buffer memory to the nth page of another free block. (Block ’B’ )
* Step3
Then, copy the data in the 1st ~ (n-1)th page to the same location of the Block ’B’ .
* Step4
Do not erase or program to Block ’A’ by creating an ’invalid Block’ table or other appropriate scheme.
When the error occurs after an erase operation, prevent future accesses to this bad block
(again by creating a table within the system or other appropriate scheme.)
During Erase operation ;
Block Replacement
Block
Frame
Single Bit
1st
(n-1)th
nth
(page)
1st
(n-1)th
nth
(page)
an error occurs.
Failure Mode
Erase Failure
Program Failure
Program Failure
("1" --> "0")
Block A
Block B
2
Buffer memory of the controller.
1
10
Read after Erase --> Block Replacement
Status Read after Program --> Block Replacement
Block Verify after Program --> Block Replacement
Detection and Countermeasure sequence
FLASH MEMORY