M25PE40VMP6P datasheet(24/60 Pages) STMICROELECTRONICS

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Instructions

M25PE40

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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 cycle is in

progress. When one of these cycles is in progress, it is recommended to 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 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, Program

or Erase cycle. When set to 1, such a cycle is in progress, when reset to 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, 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 3) becomes

protected against Page Program (PP), Page Erase (PE), Sector Erase (SE) and SubSector

Erase (SSE) 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

●

the Lock Register protection bits are not all set (‘1’)

6.4.4

SRWD bit

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

Protect (W) signal. When the Status Register Write Disable (SRWD) bit is set to 1, and Write

Protect (W) is driven Low, the non-volatile bits of the Status Register (SRWD, BP2, BP1,

BP0) become read-only bits. In such a state, as the Write Status Register (WRSR)

instruction is no longer accepted for execution, the definition of the size of the Write

Protected area cannot be further modified.

Table 7.

Status Register format(1) (2) (3)

WEL (Write Enable Latch) and WIP ((Write In Program) are volatile read-only bits (WEL is set and reset by

specific instructions; WIP is automatically set and reset by the internal logic of the device).

SRWD = Status Register Write Protect bit; BP0, BP1, BP2 = Block Protect Bits.

The BP bits and the SRWD bit exist only in the T9HX process.

SRWD

BP2

BP1

BP0

WEL

WIP

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