This Data Sheet may be revised by subsequent versions

©2004 Eon Silicon Solution, Inc., www.essi.com.tw

or modifications due to changes in technical specifications.

13

EN25B40

Rev. E, Issue Date: 2007/5/3

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.