AT25DF081A datasheet(27/54 Pages) ETC2

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8715C–SFLSH–1/2013

AT25DF081A

10.3 Read Sector Lockdown Registers

The Sector Lockdown Registers can be read to determine the current lockdown status of each physical 64-Kbyte

sector. To read the Sector Lockdown Register for a particular 64-Kbyte sector, the CS pin must first be asserted

and the opcode of 35h must be clocked in. Once the opcode has been clocked in, three address bytes designating

any address within the 64-Kbyte sector must be clocked in. After the address bytes have been clocked in, data will

be output on the SO pin during every subsequent clock cycle. The data being output will be a repeating byte of

either FFh or 00h to denote the value of the appropriate Sector Lockdown Register.

At clock frequencies above fCLK, the first byte of data output will not be valid. Therefore, if operating at clock fre-

quencies above fCLK, at least two bytes of data must be clocked out from the device in order to determine the

correct status of the appropriate Sector Lockdown Register.

Deasserting the CS pin will terminate the read operation and put the SO pin into a high-impedance state. The CS

pin can be deasserted at any time and does not require that a full byte of data be read.

Figure 10-3. Read Sector Lockdown Register

Table 10-2.

Read Sector Lockdown Register – Output Data

Output Data

Sector Lockdown Register Value

00h

Sector Lockdown Register value is 0 (sector is not locked down)

FFh

Sector Lockdown Register value is 1 (sector is permanently locked down)

SCK

MSB

00110101

410 11

812

42 43

37 38

31 32

29 30

47 48

OPCODE

AAAA

AAA

MSB

XXXXXXX

MSB

DDDDDDD

ADDRESS BITS A23-A0

DON'T CARE

DATA BYTE

HIGH-IMPEDANCE

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