AT25DF021A-DWFHT datasheet(25/59 Pages) RENESAS

25 / 59 page

DS-AT25DF021A-042 Rev. L

Page 25

8/7/23

AT25DF021A Datasheet

9.4

Unprotect Sector

Issuing the Unprotect Sector command to a particular sector address resets the corresponding Sector Protection

device has a corresponding single-bit Sector Protection Register that is used to control the software protection of

a sector.

Before the Unprotect 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 Unprotect Sector command, the CS pin

must first be asserted and the opcode of 39h must be clocked into the device. After the opcode has been clocked

in, the three address bytes designating any address within the sector to be unlocked must be clocked in. Any

additional data clocked into the device after the address bytes are ignored. When the CS pin is deasserted, the

Sector Protection Register corresponding to the sector addressed by A23 - A0 is reset to the logical 0 state, and

the sector itself is unprotected. 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 locking or unlocking of sectors, the Sector Protection Registers

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

any attempts to issue the Unprotect Sector command is ignored, and the device resets the WEL bit in the Status

Figure 22. Unprotect Sector

9.5

Global Protect/Unprotect

The Global Protect and Global Unprotect features can work in conjunction with the Protect Sector and Unprotect

Sector functions. For example, a system can globally protect the entire memory array and then use the Unprotect

Sector command to individually unprotect certain sectors and individually reprotect them later by using the Protect

Sector command. Likewise, a system can globally unprotect the entire memory array and then individually protect

certain sectors, as required.

Performing a Global Protect or Global Unprotect is done by writing a certain combination of data to the Status

execution details). The Write Status Register command is also used to modify the SPRL (Sector Protection

Registers Locked) bit to control hardware and software locking.

To perform a Global Protect, the appropriate WP pin and SPRL conditions must be met, and the system must

write a logical 1 to bits 5, 4, 3, and 2 of the Status Register. Conversely, to perform a Global Unprotect, the same

WP and SPRL conditions must be met but the system must write a logical 0 to bits 5, 4, 3, and 2 of the Status

SCK

MSB

00111001

410 11

812

29 30

27 28

Opcode

AAAA

AAA

Address Bits A23-A0

High-Impedance

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