AT45DB321D-SU-2.5 Atmel, AT45DB321D-SU-2.5 Datasheet - Page 16

• Manufacturer Part Number: AT45DB321D-SU-2.5
• Description: memory size:32mbit; supply voltage range:2.5v to 3.6v; memory case style:soic; no. of...
• Manufacturer: Atmel

8.1.2
8.2
Reading the Sector Lockdown Register
The sector lockdown register can be read to determine which sectors in the memory array are permanently locked down. To
read the sector lockdown register, the CS pin must first be asserted. Once the CS pin has been asserted, an opcode of 35H and
three dummy bytes must be clocked into the device via the SI pin. After the last bit of the opcode and dummy bytes has been
clocked in, the data for the content of the sector lockdown register will be clocked out on the SO pin. The first byte corresponds
to sector 0 (0a, 0b) the second byte corresponds to sector 1, and the last byte (byte 16) corresponds to sector 15. After the last
byte of the sector lockdown register has been read, additional pulses on the SCK pin will simply result in undefined data being
output on the SO pin.
Deasserting the CS pin will terminate the read sector lockdown register operation and put the SO pin into a high-impedance
state.
Table 8-4
Table 8-4.
Note:
Figure 8-2. Read Sector Lockdown Register
Security Register
The device contains a specialized security register that can be used for purposes such as unique device serialization or locked
key storage. The register is comprised of a total of 128 bytes that are divided into two portions. The first 64 bytes (byte locations
0 through 63) of the security register are allocated as a one-time user programmable space. Once these 64 bytes have been
programmed, they cannot be reprogrammed. The remaining 64 bytes of the register (byte locations 64 through 127) are factory
programmed by Atmel, and contain a unique value for each device. The factory programmed data are fixed and cannot be
changed.
Table 8-5.
CS
SO
Command
Read sector lockdown register
Data type
SI
Each transition
represents 8 bits
details the values read from the sector lockdown register.
Sector Lockdown Register
xx = Dummy byte.
Security Register
Opcode
0
One-time user programmable
X
1
X
· · ·
62
Security Register Byte Number
X
Byte 1
35H
Data byte
63
n
64
Data byte
Byte 2
n + 1
xxH
Atmel factory programmed
65
Atmel AT45DB321D
Byte 3
· · ·
xxH
Data byte
n + 63
3597Q–DFLASH–6/11
126
Byte 4
xxH
127
16