Rainbow Electronics AT45DB321D - Manual (Page 19)

19
3597J–DFLASH–4/08
AT45DB321D
10.1.1 Sector Lockdown Register
Sector Lockdown Register is a nonvolatile register that contains 64 bytes of data, as shown
below:
10.1.2 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 3 dummy bytes must be
clocked into the device via the SI pin. After the last bit of the opcode and dummy bytes have
been clocked in, the data for the contents 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 unde-
fined 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 10-2 details the values read from the Sector Lockdown Register.
Figure 10-2. Read Sector Lockdown Register
Sector Number 0 (0a, 0b) 1 to 63
Locked
See Below
FFH
Unlocked 00H
Table 10-1. Sector 0 (0a, 0b)
0a 0b
Bit 3, 2
Data
Value
(Pages 0-7) (Pages 8-127)
Bit 7, 6 Bit 5, 4 Bit 1, 0
Sectors 0a, 0b Unlocked 00 00 00 00 00H
Sector 0a Locked (Pages 0-7) 11 00 00 00 C0H
Sector 0b Locked (Pages 8-127) 00 11 00 00 30H
Sectors 0a, 0b Locked (Pages 0-127) 11 11 00 00 F0H
Table 10-2. Sector Lockdown Register
Command Byte 1 Byte 2 Byte 3 Byte 4
Read Sector Lockdown Register 35H xxH xxH xxH
Note: xx = Dummy Byte
Opcode X X X
Data Byte
n
Data Byte
n + 1
CS
Data Byte
n + 63
SI
SO
Each transition
represents 8 bits