AT45DB021D-MU datasheet(19/52 Pages) ATMEL

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3638B–DFLASH–02/07

AT45DB021D [Preliminary]

10.1.1

Sector Lockdown Register

Sector Lockdown Register is a nonvolatile register that contains 8 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 8) corresponds to sector 7. After the last byte of the Sector Lock-

down 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 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 7

Locked

See Below

FFH

Unlocked

00H

Table 10-1.

Sector 0 (0a, 0b)

Bit 3, 2

Data

Value

(Page 0-7)

(Page 8-127)

Bit 7, 6

Bit 5, 4

Bit 1, 0

Sectors 0a, 0b Unlocked

00H

Sector 0a Locked (Page 0-7)

C0H

Sector 0b Locked (Page 8-127)

30H

Sectors 0a, 0b Locked (Page 0-127)

F0H

Table 10-2.

Sector Lockdown Register

Command

Byte 1

Byte 2

Byte 3

Byte 4

Read Sector Lockdown Register

35H

xxH

Note:

xx = Dummy Byte

Opcode

Data Byte

n + 1

Data Byte

n + 3

Each transition

represents 8 bits

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