AT25DF161_13 datasheet(27/52 Pages) ETC2

27 / 52 page

AT25DF161

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 frequencies

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

10.4

Program OTP Security Register

The device contains a specialized OTP (One-Time Programmable) Security Register that can be used for purposes such as

unique device serialization, system-level Electronic Serial Number (ESN) storage, locked key storage, etc. The OTP

Security Register is independent of the main Flash memory array and is comprised of a total of 128-bytes of memory

divided into two portions. The first 64-bytes (byte locations 0 through 63) of the OTP Security Register are allocated as a

one-time user-programmable space. Once these 64-bytes have been programmed, they cannot be erased or

reprogrammed. The remaining 64-bytes of the OTP Security Register (byte locations 64 through 127) are factory

programmed by Adesto® and will contain a unique value for each device. The factory programmed data is fixed and cannot

be changed.

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

3687H–DFLASH–5/2013

AT25DF161 датащи(PDF) 27 Page - List of Unclassifed Manufacturers