TH58NVG1S3AFT Datasheet, PDF (30/32 Pages) Toshiba Semiconductor – TOSHIBA MOS DIGITAL INTEGRATED CIRCUIT SILICON GATE CMOS

TH58NVG1S3AFT05
(13) Invalid blocks (bad blocks)
The device occasionally contains unusable blocks. Therefore, the following issues must be recognized:
Figure 26.
Bad Block
Bad Block
At the time of shipment, all data bytes in a valid block are FFH. For
bad blocks, all bytes are not in the FFH state. Please don’t perform erase
operation to bad blocks.
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
The number of valid blocks at the time of shipment is as follows:
MIN
TYP.
MAX
UNIT
Valid (Good) Block Number
2008
-
2048
Block
Bad Block Test Flow
Start
Block No 1
Block No. Block No.  1
Read Check
Pass
Read Check : Read the 1st page or the 2nd page
of each block. If the column address
0 or 2048 of the 1st page or the 2nd
page is not FF (Hex), define the
block as a bad block.
Fail
Bad Block *1
No
Block No. 2048
Yes
End
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Figure 27.
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