EN25F40 Datasheet, PDF (11/33 Pages) Eon Silicon Solution Inc. – 4 Mbit Serial Flash Memory with 4Kbytes Uniform Sector

EN25F40
Reserved bit. Status register bit locations 5 and 6 are reserved for future use. Current devices will read 0
for these bit locations. It is recommended to mask out the reserved bit when testing the Status Register.
Doing this will ensure compatibility with future devices.
SRP bit / OTP_LOCK bit. The Status Register Protect (SRP) bit is operated in conjunction with the Write
Protect (WP#) signal. The Status Register Write Protect (SRP) bit and Write Protect (WP#) signal allow
the device to be put in the Hardware Protected mode (when the Status Register Protect (SRP) bit is set to
1, and Write Protect (WP#) is driven Low). In this mode, the non-volatile bits of the Status Register (SRP,
BP2, BP1, BP0) become read-only bits and the Write Status Register (WRSR) instruction is no longer
accepted for execution.
In OTP mode, this bit is served as OTP_LOCK bit, user can read/program/erase OTP sector as normal
sector while OTP_LOCK value is equal 0, after OTP_LOCK is programmed with 1 by WRSR command,
the OTP sector is protected from program and erase operation. The OTP_LOCK bit can only be
programmed once.
Note : In OTP mode, the WRSR command will ignore any input data and program OTP_LOCK bit to 1, user
must clear the protect bits before enter OTP mode and program the OTP code, then execute WRSR command
to lock the OTP sector before leaving OTP mode.
Write Status Register (WRSR) (01h)
The Write Status Register (WRSR) instruction allows new values to be written to the Status Register.
Before it can be accepted, a Write Enable (WREN) instruction must previously have been executed. After
the Write Enable (WREN) instruction has been decoded and executed, the device sets the Write Enable
Latch (WEL).
The Write Status Register (WRSR) instruction is entered by driving Chip Select (CS#) Low, followed by
the instruction code and the data byte on Serial Data Input (DI).
The instruction sequence is shown in Figure 8.. The Write Status Register (WRSR) instruction has no
effect on S6, S5, S1 and S0 of the Status Register. S6 and S5 are always read as 0. Chip Select (CS#)
must be driven High after the eighth bit of the data byte has been latched in. If not, the Write Status
Register (WRSR) instruction is not executed. As soon as Chip Select (CS#) is driven High, the self-timed
Write Status Register cycle (whose duration is tW) is initiated. While the Write Status Register cycle is in
progress, the Status Register may still be read to check the value of the Write In Progress (WIP) bit. The
Write In Progress (WIP) bit is 1 during the self-timed Write Status Register cycle, and is 0 when it is
completed. When the cycle is completed, the Write Enable Latch (WEL) is reset.
The Write Status Register (WRSR) instruction allows the user to change the values of the Block Protect
(BP2, BP1, BP0) bits, to define the size of the area that is to be treated as read-only, as defined in Table
3.. The Write Status Register (WRSR) instruction also allows the user to set or reset the Status Register
Protect (SRP) bit in accordance with the Write Protect (WP#) signal. The Status Register Protect (SRP) bit
and Write Protect (WP#) signal allow the device to be put in the Hardware Protected Mode (HPM). The
Write Status Register (WRSR) instruction is not executed once the Hardware Protected Mode (HPM) is
entered.
NOTE : In the OTP mode, WRSR command will ignore input data and program OTP_LOCK bit to 1.
This Data Sheet may be revised by subsequent versions ₁₁ ©2004 Eon Silicon Solution, Inc., www.essi.com.tw
or modifications due to changes in technical specifications.
Rev. B, Issue Date: 2007/05/09