Rainbow Electronics AT25DQ321 - Manual (Page 34)

34 AT25DQ321 [DATASHEET]
8718D–DFLASH–12/2012
10.2 Freeze Sector Lockdown State
The current sector lockdown state can be permanently frozen so that no further modifications to the Sector Lockdown
Registers can be made; therefore, the Sector Lockdown command will be permanently disabled and no additional
sectors can be locked down aside from those already locked down. Any attempts to issue the Sector Lockdown
command after the sector lockdown state has been frozen will be ignored.
Before the Freeze Sector Lockdown State command can be issued, the Write Enable command must have been
previously issued to set the WEL bit in the Status Register to a Logical 1. In addition, the Sector Lockdown Enabled
(SLE) bit in the Status Register must have also been previously set to the Logical 1 state. To issue the Freeze Sector
Lockdown State command, the CS pin must first be asserted and the opcode of 34h must be clocked into the device
followed by three command specific address bytes of 55AA40h. After the three address bytes have been clocked in, a
confirmation byte of D0h must be clocked in immediately following the three address bytes. Any additional data clocked
into the device will be ignored. When the CS pin is deasserted, the current sector lockdown state will be permanently
frozen within a time of t
LOCK
. In addition, the WEL bit in the Status Register will be reset back to the Logical 0 state and
the SLE bit will be permanently reset to a Logical 0 to indicate that the Sector Lockdown command is permanently
disabled.
The complete and correct three address bytes and the confirmation byte must be clocked into the device before the CS
pin is deasserted and the CS pin must be deasserted on a byte boundary (multiples of eight bits); otherwise, the device
will abort the operation. When the device aborts the Freeze Sector Lockdown State operation, the WEL bit in the Status
Register will be reset to a Logical 0; however, the state of the SLE bit will be unchanged.
Figure 10-2. Freeze Sector Lockdown State
SO
SI
SCK
CS
MSB MSB
2 3 1 0
0 0 1 1 0 1 0 0
6 7 5 4 9 8 39 37 38 33 36 35 34 31 32 29 30
Opcode
High-impedance
0 1 0 0 0 0
MSB
1 1 0 1 0 0 0 0
Address Bits A23-A0 Confirmation Byte IN