M25P128 datasheet(22/41 Pages) STMICROELECTRONICS

22 / 41 page

Instructions

M25P128

22/41

Rev. 1

Latch (WEL) bit has previously been set by a Write Enable (WREN) instruction, regardless

of the whether Write Protect (W) is driven High or Low.

When the Status Register Write Disable (SRWD) bit of the Status Register is set to 1, two

cases need to be considered, depending on the state of Write Protect (W):

●

If Write Protect (W) is driven High, it is possible to write to the Status Register provided

that the Write Enable Latch (WEL) bit has previously been set by a Write Enable

(WREN) instruction.

●

If Write Protect (W) is driven Low, it is not possible to write to the Status Register even

if the Write Enable Latch (WEL) bit has previously been set by a Write Enable (WREN)

instruction. (Attempts to write to the Status Register are rejected, and are not accepted

for execution). As a consequence, all the data bytes in the memory area that are

software protected (SPM) by the Block Protect (BP2, BP1, BP0) bits of the Status

Regardless of the order of the two events, the Hardware Protected Mode (HPM) can be

entered:

●

by setting the Status Register Write Disable (SRWD) bit after driving Write Protect (W)

Low

●

or by driving Write Protect (W) Low after setting the Status Register Write Disable

(SRWD) bit.

The only way to exit the Hardware Protected Mode (HPM) once entered is to pull Write

Protect (W) High.

If Write Protect (W) is permanently tied High, the Hardware Protected Mode (HPM) can

never be activated, and only the Software Protected Mode (SPM), using the Block Protect

(BP2, BP1, BP0) bits of the Status Register, can be used.

Figure 12. Write Status Register (WRSR) Instruction Sequence

AI02282D

3456789 10 11 12 13 14 15

High Impedance

Instruction

Status

765432

MSB

M25P128 Datasheet(PDF) 22 Page - STMicroelectronics