GD25B257D datasheet(66/92 Pages) GIGADEVICE

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3.3V Uniform Sector

Dual and Quad Serial Flash

GD25B257D

8.35.

Erase Security Registers (44H)

The GD25B257D provides three 2048-Byte Security Registers which can be erased and programmed individually.

These registers may be used by the system manufacturers to store security and other important information separately from

the main memory array.

The Erase Security Registers command is similar to Sector/Block Erase command. A Write Enable (WREN) command

must previously have been executed to set the Write Enable Latch (WEL) bit.

The Erase Security Registers command sequence: CS# goes low  sending Erase Security Registers command 

The Erase Security Registers command sequence: CS# goes low  sending Erase Security Registers command 3 or 4-

Byte address on SI  CS# goes high. The command sequence is shown below. CS# must be driven high after the eighth

bit of the last address Byte has been latched in; otherwise the Erase Security Registers command is not executed. As soon

as CS# is driven high, the self-timed Erase Security Registers cycle (whose duration is tSE) is initiated. While the Erase

Security Registers cycle is in progress, the Status Register may be read to check the value of the Write in Progress (WIP)

bit. The Write in Progress (WIP) bit is 1 during the self-timed Erase Security Registers cycle, and is 0 when it is completed.

At some unspecified time before the cycle is completed, the Write Enable Latch (WEL) bit is reset. The Security Registers

Lock Bit (LB3-1) in the Status Register can be used to OTP protect the security registers. Once the LB bit is set to 1, the

Security Registers will be permanently locked; the Erase Security Registers command will be ignored.

Table 17. Security Registers

Address

A23-16

A15-12

A11

A10-0

Security Register #1

00H

0 0 0 1

Don’t care

Security Register #2

00H

0 0 1 0

Don’t care

Security Register #3

00H

0 0 1 1

Don’t care

Figure 72. Erase Security Registers command Sequence Diagram (ADS=0)

Figure 73.Erase Security Registers command Sequence Diagram (ADS=1)

Command

44H

CS#

SCLK

29 30 31

MSB

24 Bits Address

23 22

Command

44H

CS#

SCLK

37 38 39

MSB

32 Bits Address

31 30

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