AT45DB641E Datasheet, PDF (22/72 Pages) List of Unclassifed Manufacturers – 64-Mbit DataFlash (with Extra 2-Mbits), 1.7V Minimum SPI Serial Flash Memory

Figure 7-5. Program Sector Protection Register
CS
SI
3Dh
2Ah
7Fh
Each transition represents eight bits
FCh
Data Byte
n
Data Byte
n+1
Data Byte
n + 31
7.3.3
Read Sector Protection Register
To read the Sector Protection Register, an opcode of 32h and three dummy bytes must be clocked into the device. After
the last bit of the opcode and dummy bytes have been clocked in, any additional clock pulses on the SCK pin will result
in the Sector Protection Register contents being output on the SO pin. The first byte (byte location 0) corresponds to
Sector 0 (0a and 0b), the second byte corresponds to Sector 1, and the last byte (byte location 31) corresponds to 
Sector 31. Once the last byte of the Sector Protection Register has been clocked out, any additional clock pulses will
result in undefined data being output on the SO pin. The CS pin must be deasserted to terminate the Read Sector
Protection Register operation and put the output into a high-impedance state.
Table 7-8. Read Sector Protection Register Command
Command
Read Sector Protection Register
Note: 1. XX = Dummy byte
Figure 7-6. Read Sector Protection Register
CS
Byte 1
32h
Byte 2
XXh
Byte 3
XXh
Byte 4
XXh
SI
32h
XX
XX
SO
Each transition represents eight bits
XX
Data
n
Data
n+1
Data
n + 31
7.3.4
About the Sector Protection Register
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 application’s life
cycle. If the application requires that the Security 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 disabling sector protection completely will need to
be implemented by the application to ensure that the limit of 10,000 cycles is not exceeded.
AT45DB641E 22
DS-45DB641E-027E–DFLASH–1/2014