AT26DF161_06 Datasheet, PDF (14/35 Pages) ATMEL Corporation – 16-megabit 2.7-volt Only Serial Firmware DataFlash Memory

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
CS
SCK
SI
SO
0 1 2 3 4 5 6 7 8 9 10 11 12
26 27 28 29 30 31
OPCODE
ADDRESS BITS A23-A0
0 0 1 1 1 0 0 1AAAAAA
MSB
MSB
AAAAAA
HIGH-IMPEDANCE
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 page 21 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. Table 9-2 details the conditions
necessary for a Global Protect or Global Unprotect to be performed.
14 AT26DF161
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