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NX25F011B View Datasheet(PDF) - Unspecified

Part NameDescriptionManufacturer
NX25F011B 1M-BIT, 2M-BIT, AND 4M-BIT SERIAL FLASH MEMORIES WITH 4-PIN SPI INTERFACE ETC1
Unspecified 
NX25F011B Datasheet PDF : 37 Pages
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NX25F011B
NX25F021B
NX25F041B
Sector Format
The memory array of standard Serial Flash devices are
factory programmed to a full erase state with all bits set to
1(FFH). NexFlash also offers restricted sector devices
(with -Rsuffix) which may provide a more cost effective
alternative to standard devices that have 100% valid
sectors. Restricted sector devices have a limited number
of sectors that do not meet manufacturing programming
criteria over the specified operating range. The first bye of
each good sector in a -Rdevice is pre-programmed during
manufacturing with a tag/sync value of C9H. Although this
byte location of the sector can be changed, it is recom-
mended that it be maintained and incorporated into the
applications sector formatting. The tag/sync values serve
two purposes. First, they provide a sync-detect that can
help verify if the command sequence was clocked into the
device properly. Secondly, they serve as a tag to identify
a fully functional (valid) sector. For defective sectors, the
first byte is tagged with a pattern other than C9H. In addition
to individual sector tagging, all restricted sectors for a given
device are listed in the Device Information Sector. For more
information see the latest version of Device Information
Sector Application Note SFAN-02.
High Data Integrity Applications
Data storage applications that use Flash memory or other
non-volatile media must take into consideration the possi-
bility of noise or other adverse system conditions that may
affect data integrity. For those applications that require
higher levels of data integrity it is a recommended practice
to use Error Correcting Code (ECC) techniques. The
NexFlash Serial Flash Development Kit provides a software
routine for a 32-bit ECC that can detect up to two bit errors
and correct one. The ECC not only minimizes problems
caused by system noise but can also extend Flash memory
endurance.
Write/Verify Flow
For those systems without the processing power to handle
ECC algorithms, a simple verification after writeis recom-
mended. The write verify can be done quickly (less than tXS)
using the Compare Sector command. The compare result
can be checked in the Status Register. If compare is not
equal (CNE=1) then a sector rewrite should be done using
the Transfer to Sector command (Figure 12). A single retry
is adequate for most applications. However, if an applica-
tion requires extended endurance additional retrys can be
added. The Serial Flash Development Kit software includes
a simple Write/Verify routine that will compare data written
to a given sector and rewrite the sector if the compare is
not correct.
Grouping Static and Frequently
Updated Data
1 In the NX25F011B/021B/041B a data block is every 32
sectors starting from sector 0; that is, block 0 is sector
0 - 31, block 1 is sector 32 - 63 and so on. Refer to figure
4. For the highest data integrity, it is important to separate
2 static data (configuration settings, tables) and frequently
updated data (streaming voice/image or data acquisition)
into separate blocks. Following this convention optimizes
the environment for the data stored in the flash cells within
each block.
3
4
Write Verify
Write to SRAM Command
5
Transfer SRAM to Sector Command
6
7
Ready?
NO
Programming
Done?
8
YES
Compare Sector with SRAM Command
9
NO
Equivalent
10
Retry
Retry
YES
Counter
No More
11
Retries
Return
Error
12
Figure 12. Write/Verify Flow
NexFlash Technologies, Inc.
29
PRELIMINARY NXSF016F-1201
12/12/01 ©
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