NX25F080A-3TE-R Ver la hoja de datos (PDF) - NexFlash -> Winbond Electronics

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NX25F080A-3TE-R

8M-BIT SERIAL FLASH MEMORY WITH 4-PIN SPI INTERFACE

NexFlash -> Winbond Electronics 

NX25F080A

Sector Format and Tag/Sync Bytes

The first byte of each sector is pre-programmed during

manufacturing with a tag/sync value of “C9H”. Although

this byte location of the sector can be changed, it is

recommended that it be maintained and incorporated into

the application’s sector formatting.

The tag/sync values serve two purposes. First, they pro-

vide 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. This is especially important if “restricted sector”

devices are ever to be used. Restricted sector devices

provide a more cost effective alternative to standard

devices with 100% valid sectors. Restricted sector devices

have a limited number of sectors that do not meet manufac-

turing programming criteria over the specified operating

range. When such a sector is detected, the first three bytes

are 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 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 soft-

ware 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. For those systems without the

processing power to handle ECC algorithms, a simple

“verification after write” is recommended (Figure 12). 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.

Write Verify

Write to SRAM Command

Transfer SRAM to Sector Command

Ready?

NO

Programming

Done?

YES

Compare Sector with SRAM Command

NO

Equivalent

YES

Return

Retry

Counter

Retry

No More

Retries

Error

Figure 12. Write/Verify Flow for High Data Integrity

Applications

20

NexFlash Technologies, Inc.

PRELIMINARY NXSF005C-0699

06/11/99 ©

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