AT45DB321C datasheet(12/37 Pages) ATMEL

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AT45DB321C [Preliminary]

3387B–DFLSH–9/04

Security Register

The AT45DB321C contains a specialized register that can be used for security pur-

poses in system design. The Security Register is a unique 128-byte register that is

divided into two portions. The first 64 bytes (byte 0 to byte 63) of this page are allocated

as a one-time user programmable space. Once these 64 bytes have been programmed,

they should not be reprogrammed. The remaining 64 bytes of this page (byte 64 to byte

127) are factory programmed by Atmel and will contain a unique number for each

device. The factory programmed data is fixed and cannot be changed.

The Security Register can be read by clocking in opcode 77H to the device followed by

three address bytes (which are comprised of 14 don’t care bits plus 10 address bits) and

32 don’t care clock cycles. See the opcode table on page 17.

To program the first 64 bytes of the Security Register, a two step sequence must be

used. The first step requires that the user loads the desired data into Buffer 1 by using

the Buffer 1 Write operation (opcode 84H – see Buffer Write description on page 5). The

user should specify the starting buffer address as location zero and should write a full

64 bytes of information into the buffer. Otherwise, the first 64 bytes of the buffer may

contain data that was previously stored in the buffer. It is not necessary to fill the remain-

ing 464 bytes (byte locations 64 through 127) of the buffer with data. After the Buffer 1

Write operation has been completed, the Security Register can be subsequently pro-

grammed by reselecting the device and clocking in opcode 9AH into the device followed

by three don’t care bytes (24 clock cycles). After the final don’t care clock cycle has

been completed, a low-to-high transition on the CS pin will cause the device to initiate

an internally self-timed program operation in which the contents of Buffer 1 will be pro-

grammed into the Security Register. Only the first 64 bytes of data in Buffer 1 will be

programmed into the Security Register; the remaining 464 bytes of the buffer will be

ignored. The Security Register program operation should take place in a maximum time

of t

Operation Mode

Summary

The modes described can be separated into two groups – modes that make use of the

Flash memory array (Group A) and modes that do not make use of the Flash memory

array (Group B).

Group A modes consist of:

Main Memory Page Read

Continuous Array Read

Main Memory Page to Buffer 1 (or 2) Transfer

Buffer 1 (or 2) to Main Memory Page Program with Built-in Erase

Buffer 1 (or 2) to Main Memory Page Program without Built-in Erase

Main Memory Page Program through Buffer 1 (or 2)

Page Erase

Block Erase

Auto Page Rewrite

Group B modes consist of:

Buffer 1 (or 2) Read

Buffer 1 (or 2) Write

Status Register Read

Manufacturer and Device ID Read

If a Group A mode is in progress (not fully completed), then another mode in Group A

should not be started. However, during this time in which a Group A mode is in

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