M25P40 datasheet(22/53 Pages) STMICROELECTRONICS

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Instructions

M25P40

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6.4

Read Status Register (RDSR)

The Read Status Register (RDSR) instruction allows the Status Register to be read. The

Status Register may be read at any time, even while a Program, Erase or Write Status

check the Write In Progress (WIP) bit before sending a new instruction to the device. It is

also possible to read the Status Register continuously, as shown in Figure 10.

The status and control bits of the Status Register are as follows:

6.4.1

WIP bit

The Write In Progress (WIP) bit indicates whether the memory is busy with a Write Status

0 no such cycle is in progress.

6.4.2

WEL bit

The Write Enable Latch (WEL) bit indicates the status of the internal Write Enable Latch.

When set to 1 the internal Write Enable Latch is set, when set to 0 the internal Write Enable

Latch is reset and no Write Status Register, Program or Erase instruction is accepted.

6.4.3

BP2, BP1, BP0 bits

The Block Protect (BP2, BP1, BP0) bits are non-volatile. They define the size of the area to

be software protected against Program and Erase instructions. These bits are written with

the Write Status Register (WRSR) instruction. When one or more of the Block Protect (BP2,

BP1, BP0) bits is set to 1, the relevant memory area (as defined in Table 2) becomes

protected against Page Program (PP) and Sector Erase (SE) instructions. The Block Protect

(BP2, BP1, BP0) bits can be written provided that the Hardware Protected mode has not

been set. The Bulk Erase (BE) instruction is executed if, and only if, all Block Protect (BP2,

BP1, BP0) bits are 0.

6.4.4

SRWD bit

The Status Register Write Disable (SRWD) bit is operated in conjunction with the Write

Protect (W) signal. The Status Register Write Disable (SRWD) bit and Write Protect (W)

signal allow the device to be put in the Hardware Protected mode (when the Status Register

Write Disable (SRWD) bit is set to 1, and Write Protect (W) is driven Low). In this mode, the

non-volatile bits of the Status Register (SRWD, BP2, BP1, BP0) become read-only bits and

the Write Status Register (WRSR) instruction is no longer accepted for execution.

Table 6.

Status Register format

SRWD

BP2

BP1

BP0

WEL

WIP

Status Register Write Protect

Block Protect bits

Write Enable Latch bit

Write In Progress bit

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