5 global protect/unprotect – Rainbow Electronics AT25DF081 User Manual
Page 15
15
3674E–DFLASH–8/08
AT25DF081
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
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.
Unprotect Sector
9.5
Global Protect/Unprotect
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 command (see “Write Status
Register” section on
for command execution details). The Write Status Register com-
mand 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 per-
form 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 Register.
details the conditions
necessary for a Global Protect or Global Unprotect to be performed.
SCK
CS
SI
SO
MSB
MSB
2
3
1
0
0
0
1
1
1
0
0
1
6
7
5
4
10 11
9
8
12
31
29 30
27 28
26
OPCODE
A
A
A
A
A
A
A
A
A
A
A
A
ADDRESS BITS A23-A0
HIGH-IMPEDANCE