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NX25F080A-5TI-R

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

NexFlash -> Winbond Electronics 

NX25F080A

The Compare Sector command allows the contents of the

SRAM to be compared with the specified sector in memory.

The result of the compare is set in the Status Register. This

command can be useful for verifying a sector after write

(see High Data Integrity Applications towards the end of

this data sheet). It is also useful when rewriting

multi-sector files that have only minor changes from the

previous write. If the new data in the SRAM is the same as

the previously written data, the sector write can be skipped.

Used in this way, the command saves time that would have

been used for re-programming. It also extends the endur-

ance of the Flash memory cells.

Using the SRAM independently of Flash Memory

The SRAM can be used independently of the Flash memory

operations for look-up tables, variable storage, or

scratch-pad purposes. If the Flash memory needs to be

written to while the SRAM is being used for a different

purpose, the contents can be temporarily stored to a sector

and then transferred back again when needed. The SRAM

can be especially useful for RAM-limited microcontroller-

based systems, eliminating the need for external SRAM

and freeing pins for other purposes. It can also make it

possible to use small pin-count microcontrollers, since only

a few pins are needed for the interface instead of the 20-40

pins required for parallel bus-oriented Flash devices.

If more than 536 bytes of SRAM are needed, the Transfer

SRAM to Program Buffer, Transfer Program Buffer to SRAM,

and the Read Program Buffer commands can be used to

expand the storage to 1072 bytes. In this mode of

operation, all writes must be handled through the

536-byte SRAM and the Program buffer is essentially used

as a stack.

Write Protection

The NX25F080A provide advanced software and hard-

ware write protection features. Software-controlled write

protection of the entire array is handled using the

Write Enable and Write Disable commands. Hardware

write protection is possible using the Write Protect pin (WP).

Write-protecting a portion of Flash memory is accommo-

dated by programming a write protect range in the

Configuration Register. For applications needing a portion of

the memory to be permanently write-protected, a one-time

programmable write protection feature is supported.

Contact NexFlash for further information.

Configuration Register

The Configuration Register stores the current Configura-

tion of the HOLD-R/B pin, read clock edge, write protect

range, and alternate oscillator frequency (Figure 6). The

Configuration Register is accessed using the Write and

Read Configuration Register commands. A non-volatile

register, the Configuration Register will maintain its setting

even when power is removed.

CF15:9

(RESERVED)

CF8 CF7 CF6 CF5 CF4 CF3 CF2 CF1 CF0

AF WR3 WR2 WR1 WR0 WD RCE HR1 HR0

ALTERNATE OSCILATOR

FREQUENCY

WRITE PROTECT

RANGE

WRITE PROTECT

DIRECTION

READ DATA

CLOCK EDGE

HOLD-READY/BUSY

PIN FUNCTION

Figure 6. Configuration Register Bit Locations

6

NexFlash Technologies, Inc.

PRELIMINARY NXSF005C-0699

06/11/99 ©

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