D a t a S h e e t ( P r e l i m i n a r y )
9.2
Bad Block Management
Devices with Bad Blocks have the same quality level and the same AC and DC characteristics as devices
where all the blocks are valid. A Bad Block does not affect the performance of valid blocks because it is
isolated from the bit line and common source line by a select transistor. The devices are supplied with all the
locations inside valid blocks erased (FFh). The Bad Block Information is written prior to shipping. Any block
where the 1st byte in the spare area of the 1st or 2nd page does not contain FFh is a Bad Block. That is, if the
first page has an FF value and should have been a non-FF value, then the non-FF value in the second page
will indicate a bad block.The Bad Block Information must be read before any erase is attempted, as the Bad
Block Information may be erased. For the system to be able to recognize the Bad Blocks based on the
original information, it is recommended to create a Bad Block table following the flowchart shown in
Figure 9.2. The host is responsible to detect and track bad blocks, both factory bad blocks and blocks that
may go bad during operation. Once a block is found to be bad, data should not be written to that block.The 1st
block, which is placed on 00h block address is guaranteed to be a valid block.
Figure 9.2 Bad Block Management Flowchart
Start
Block Address=
Block 0
Increment
Block Address
Data(1)
No
Update
Bad Block Table
=FFh?
Yes
No
Last
Block?
Yes
End
Note:
1. Check FFh at 1st byte in the spare area of the 1st and 2nd page.
September 6, 2012 S34ML01G1_04G1_10
Spansion® SLC NAND Flash Memory for Embedded
69
SPANSION [ SPANSION ]
