TC581282AXB Datasheet, PDF (29/31 Pages) Toshiba Semiconductor – 128-MBIT (16M X 8 BITS) CMOS NAND E2PROM

TC581282AXB
(13) Invalid blocks (bad blocks)
The device contains unusable blocks. Therefore, at the time of use, please check whether a block is bad and
do not use these bad blocks.
Bad Block
Bad Block
At the time of shipment, all data bytes in a Valid Block are FFH. For Bad
Block, all bytes are not in the FFH state. Please don’t perform erase
operation to Bad Block.
Check if the device has any bad blocks after installation into the system.
Figure 27 shows the test flow for bad block detection. Bad blocks which are
detected by the test flow must be managed as unusable blocks by the
system.
A bad block does not affect the performance of good blocks because it is
isolated from the Bit line by the Select gate
Figure 26.
The number of valid blocks at the time of shipment is as follows:
MIN
TYP.
MAX
UNIT
Valid (Good) Block Number
1004

1024
Block
Bad Block Test Flowç
Start
Block No = 1
Block No. = Block No. + 1
Read Check
Pass
Read Check: to verify all pages in the block
with FF (Hex)
Fail
Bad Block *1
No
Block No. = 1024
Yes
End
*1: No erase operation is allowed to detected bad blocksç
Figure 27
2001-12-04 29/31