AT25DF641A-MH-T ATMEL [ATMEL Corporation], AT25DF641A-MH-T Datasheet - Page 23

• Manufacturer Part Number: AT25DF641A-MH-T
• Description: 64-Mbit 2.7V Minimum Serial Peripheral Interface Serial Flash Memory
• Manufacturer: ATMEL [ATMEL Corporation]

9.5
8693A–DFLASH–8/10
Global Protect/Unprotect
As a safeguard against accidental or erroneous locking or unlocking of sectors, the Sector Pro-
tection Registers can themselves be locked from updates by using the SPRL (Sector Protection
Registers Locked) bit of the Status Register (please refer to the Status Register description for
more details). If the Sector Protection Registers are locked, then any attempts to issue the
Unprotect Sector command will be ignored, and the device will reset 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 9-4.
The Global Protect and Global Unprotect features can work in conjunction with the Protect Sec-
tor 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 sec-
tors 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 sec-
tors as needed.
Performing a Global Protect or Global Unprotect is accomplished by writing a certain combina-
tion of data to the Status Register using the Write Status Register Byte 1 command (see
Status Register Byte 1” on page 38
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 five, four, three, and two of the first byte of the Status Reg-
ister. 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 five, four, three, and two of the first byte of the
Status Register.
tect to be performed.
Sectors that have been erase or program suspended must remain in the unprotected state. If a
Global Protect operation is attempted while a sector is erase or program suspended, the protec-
tion operation will abort, the protection states of all sectors in the Flash memory array will not
change, and WEL bit in the Status Register will be reset back to a logical “0”.
SCK
SO
CS
SI
Unprotect Sector
Table 9-2
HIGH-IMPEDANCE
MSB
0
0
0
details the conditions necessary for a Global Protect or Global Unpro-
1
1
2
OPCODE
1
Atmel AT25DF641A [Preliminary]
3
1
4
for command execution details). The Write Status Register
0
5
0
6
1
7
MSB
A
8
A
9
A
10 11
A
ADDRESS BITS A23-A0
A
12
A
A
26
A
27 28
A
A
29 30
A
A
31
“Write
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