FLASH MEMORY
17
K9F1208U0B
K9F1208D0B
Advance
NAND Flash Technical Notes
(Continued)
Error in write or read operation
Within 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.
Program Flow Chart
Start
I/O 6 = 1
or R/B = 1
Write 00h
I/O 0 = 0
No
*
If ECC is used, this verification
operation is not needed.
Write 80h
Write Address
Write Data
Write 10h
Read Status Register
Write Address
Wait for tR Time
Verify Data
No
Program Completed
Program Error
Yes
No
Yes
*
Program Error
Yes
: If program operation results in an error, map out
the block including the page in error and copy the
target data to another block.
*
Failure Mode
Detection and Countermeasure sequence
Write
Erase Failure
Status Read after Erase --> Block Replacement
Program Failure
Status Read after Program --> Block Replacement
Read back ( Verify after Program) --> Block Replacement
or ECC Correction
Read
Single Bit Failure
Verify ECC -> ECC Correction
ECC
: Error Correcting Code --> Hamming Code etc.
Example) 1bit correction & 2bit detection