AT25DF021A-DWFHT datasheet(24/59 Pages) RENESAS

24 / 59 page

DS-AT25DF021A-042 Rev. L

Page 24

8/7/23

AT25DF021A Datasheet

9.3

Protect Sector

Every physical sector of the device has a corresponding single-bit Sector Protection Register that is used to

control the software protection of a sector. Upon device power-up or after a device reset, each Sector Protection

erased.

Issuing the Protect Sector command to a particular sector address sets the corresponding Sector Protection

Before the Protect Sector command can be issued, the Write Enable command must have been previously issued

to set the WEL bit in the Status Register to a logical 1. To issue the Protect Sector command, the CS pin must first

be asserted and the opcode of 36h must be clocked into the device followed by three address bytes designating

any address within the sector to be protected. Any additional data clocked into the device is ignored. When the CS

pin is deasserted, the Sector Protection Register corresponding to the physical sector addressed by A23 - A0 is

set to the logical 1 state, and the sector itself is then protected from program and erase operations. Also, the WEL

bit in the Status Register is reset back to the logical 0 state.

The complete three address bytes must be clocked into the device before the CS pin is deasserted, and the CS

pin must be deasserted on an even byte boundary (multiples of eight bits); otherwise, the device stops the

operation, the state of the Sector Protection Register is unchanged, and the WEL bit in the Status Register is reset

to a logical 0.

As a safeguard against accidental or erroneous protecting or unprotecting of sectors, the Sector Protection

Registers can themselves be locked from updates by using the SPRL (Sector Protection Registers Locked) bit of

the Status Register (see the Status Register description for more details). If the Sector Protection Registers are

locked, then any attempts to issue the Protect Sector command is ignored, and the device resets the WEL bit in

the Status Register back to a logical 0 and return to the idle state once the CS pin has been deasserted.

Figure 21. Protect Sector

Table 3. Sector Protection Register Values

Value

Sector Protection Status

Sector is unprotected and can be programmed and erased.

Sector is protected and cannot be programmed or erased. This is the default state.

SCK

MSB

00110110

410 11

812

29 30

27 28

OPCODE

AAAA

AAA

ADDRESS BITS A23-A0

High-Impedance

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