AT45DB642D-CNU SL954 Atmel, AT45DB642D-CNU SL954 Datasheet - Page 18

• Manufacturer Part Number: AT45DB642D-CNU SL954
• Manufacturer: Atmel

Specifications of AT45DB642D-CNU SL954

• Density: 64Mb
• Access Time (max): 6ns
• Interface Type: Parallel/Serial-SPI
• Address Bus: 1/8Bit
• Operating Supply Voltage (typ): 3.3V
• Operating Temp Range: -40C to 85C
• Package Type: CASON
• Program/erase Volt (typ): 2.7 to 3.6V
• Sync/async: Synchronous
• Operating Temperature Classification: Industrial
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (max): 3.6V
• Word Size: 8b
• Number Of Words: 8M
• Supply Current: 15mA
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / Rohs Status: Compliant

9.1.4
10. Security Features
10.1
Figure 10-1. Sector Lockdown
18
SI or IO
Sector Lockdown
AT45DB642D
Various Aspects About the Sector Protection Register
7
- IO
CS
0
Each transition
represents 8 bits
The Sector Protection Register is subject to a limit of 10,000 erase/program cycles. Users are
encouraged to carefully evaluate the number of times the Sector Protection Register will be
modified during the course of the applications’ life cycle. If the application requires that the Sec-
tor Protection Register be modified more than the specified limit of 10,000 cycles because the
application needs to temporarily unprotect individual sectors (sector protection remains enabled
while the Sector Protection Register is reprogrammed), then the application will need to limit this
practice. Instead, a combination of temporarily unprotecting individual sectors along with dis-
abling sector protection completely will need to be implemented by the application to ensure that
the limit of 10,000 cycles is not exceeded.
The device incorporates a Sector Lockdown mechanism that allows each individual sector to be
permanently locked so that it becomes read only. This is useful for applications that require the
ability to permanently protect a number of sectors against malicious attempts at altering program
code or security information. Once a sector is locked down, it can never be erased or pro-
grammed, and it can never be unlocked.
To issue the Sector Lockdown command, the CS pin must first be asserted as it would be for
any other command. Once the CS pin has been asserted, the appropriate 4-byte opcode
sequence must be clocked into the device in the correct order. The 4-byte opcode sequence
must start with 3DH and be followed by 2AH, 7FH, and 30H. After the last byte of the command
sequence has been clocked in, then three address bytes specifying any address within the sec-
tor to be locked down must be clocked into the device. After the last address bit has been
clocked in, the CS pin must then be deasserted to initiate the internally self-timed lockdown
sequence.
The lockdown sequence should take place in a maximum time of t
Register will indicate that the device is busy. If the device is powered-down before the comple-
tion of the lockdown sequence, then the lockdown status of the sector cannot be guaranteed. In
this case, it is recommended that the user read the Sector Lockdown Register to determine the
status of the appropriate sector lockdown bits or bytes and reissue the Sector Lockdown com-
mand if necessary.
Command
Sector Lockdown
Opcode
Byte 1
Opcode
Byte 2
Opcode
Byte 3
Byte 1
3DH
Opcode
Byte 4
Address
Bytes
Byte 2
2AH
Address
Bytes
P
, during which time the Status
Byte 3
7FH
Address
Bytes
3542K–DFLASH–04/09
Byte 4
30H