AT45DB021D_09 datasheet(21/54 Pages) ATMEL

21 / 54 page

3638I–DFLASH–04/09

AT45DB021D

10.2.2

Reading the Security Register

The Security Register can be read by first asserting the CS pin and then clocking in an opcode

of 77H followed by three dummy bytes. After the last don’t care bit has been clocked in, the con-

tent of the Security Register can be clocked out on the SO pins. After the last byte of the

Security Register has been read, additional pulses on the SCK pin will simply result in undefined

data being output on the SO pins.

Deasserting the CS pin will terminate the Read Security Register operation and put the SO pins

into a high-impedance state.

Figure 10-4. Read Security Register

11. Additional Commands

11.1 Main Memory Page to Buffer Transfer

A page of data can be transferred from the main memory to the buffer. To start the operation for

the DataFlash standard page size (264 bytes), a 1-byte opcode, 53H, must be clocked into the

device, followed by three address bytes comprised of 5 don’t care bits, 10 page address bits

(PA9 - PA0), which specify the page in main memory that is to be transferred, and 9 don’t care

bits. To perform a main memory page to buffer transfer for the binary page size (256 bytes), the

opcode 53H must be clocked into the device followed by three address bytes consisting of 6

don’t care bits, 10 page address bits (A17 - A8) which specify the page in the main memory that

is to be transferred, and 8 don’t care bits. The CS pin must be low while toggling the SCK pin to

load the opcode and the address bytes from the input pin (SI). The transfer of the page of data

from the main memory to the buffer will begin when the CS pin transitions from a low to a high

state. During the transfer of a page of data (tXFR), the status register can be monitored to deter-

mine whether the transfer has been completed.

11.2 Main Memory Page to Buffer Compare

A page of data in main memory can be compared to the data in the buffer. To initiate the opera-

tion for the DataFlash standard page size, a 1-byte opcode, 60H, must be clocked into the

device, followed by three address bytes consisting of 5 don’t care bits, 10 page address bits

(PA9 - PA0) that specify the page in the main memory that is to be compared to the buffer, and

9 don’t care bits. To start a main memory page to buffer compare for a binary page size, the

opcode 60H must be clocked into the device followed by three address bytes consisting of 6

don’t care bits, 10 page address bits (A17 - A8) that specify the page in the main memory that is

to be compared to the buffer, and 8 don’t care bits. The CS pin must be low while toggling the

SCK pin to load the opcode and the address bytes from the input pin (SI). On the low-to-high

transition of the CS pin, the data bytes in the selected main memory page will be compared with

Opcode

Data Byte

n + 1

Data Byte

n + x

Each transition

represents 8 bits

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