NX25F011B Ver la hoja de datos (PDF) - Unspecified

Número de pieza

componentes Descripción

Fabricante

NX25F011B

1M-BIT, 2M-BIT, AND 4M-BIT SERIAL FLASH MEMORIES WITH 4-PIN SPI INTERFACE

Unspecified 

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 “-R” suffix) 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 “-R” device 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

application’s 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 write” is 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 ©

Share Link: