GD25VQ40CSIG datasheet(34/56 Pages) GIGADEVICE

34 / 56 page

Uniform Sector

Dual and Quad Serial Flash

GD25VQ40C

Figure31. Program/Erase Resume Sequence Diagram

7.27.

Erase Security Registers (44H)

The GD25VQ40C provides four 256-byte Security Registers which can be read 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 

CS# goes high. The command sequence is shown in Figure32. CS# must be driven high after the eighth bit of the command

code 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 (LB) in the Status

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

Address

A23-A16

A15-A8

A9-A0

Security Registers

00000000

000000

Don’t Care

Figure32. Erase Security Registers command Sequence Diagram

7.28.

Program Security Registers (42H)

The Program Security Registers command is similar to the Page Program command. It allows from 1 to 256 bytes

Security Registers data to be programmed. A Write Enable (WREN) command must previously have been executed to set

the Write Enable Latch (WEL) bit before sending the Program Security Registers command. The Program Security Registers

command is entered by driving CS# Low, followed by the command code (42H), three address bytes and at least one data

byte on SI. As soon as CS# is driven high, the self-timed Program Security Registers cycle (whose duration is tPP) is

Command

44H

CS#

SCLK

29 30 31

MSB

24 Bits Address

23 22

Command

7AH

CS#

SCLK

Resume Erase/Program

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