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 pin. 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 pin
into a high-impedance state.
Figure 10-4. Read Security Register
CS
SI
Opcode
X
X
X
Data Byte
n
Data Byte
n + 1
Data Byte
n + x
SO
Each transition
represents 8 bits
11. Additional Commands
11.1 Main Memory Page to Buffer Transfer
A page of data can be transferred from the main memory to either buffer 1 or buffer 2. To start
the operation for the DataFlash standard page size (264-bytes), a 1-byte opcode, 53H for buffer
1 and 55H for buffer 2, must be clocked into the device, followed by three address bytes com-
prised of three don’t care bits, 12 page address bits (PA11 - PA0), which specify the page in
main memory that is to be transferred, and nine don’t care bits. To perform a main memory page
to buffer transfer for the binary page size (256-bytes), the opcode 53H for buffer 1 or 55H for buf-
fer 2, must be clocked into the device followed by three address bytes consisting of four don’t
care bits, 12 page address bits (A19 - A8) which specify the page in the main memory that is to
be transferred, and eight 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 read to determine
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 buffer 1 or buffer 2. To initiate
the operation for DataFlash standard page size, a 1-byte opcode, 60H for buffer 1 and 61H for
buffer 2, must be clocked into the device, followed by three address bytes consisting of three
don’t care bits, 12 page address bits (PA11 - PA0) that specify the page in the main memory that
is to be compared to the buffer, and nine don’t care bits. To start a main memory page to buffer
compare for a binary page size, the opcode 60H for buffer 1 or 61H for buffer 2, must be clocked
into the device followed by three address bytes consisting of four don’t care bits, 12 page
address bits (A19 - A8) that specify the page in the main memory that is to be compared to the
buffer, and eight 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 the data bytes in buffer
1 or buffer 2. During this time (tCOMP), the status register will indicate that the part is busy. On
20
AT45DB081D
3596O–DFLASH–1/2013
ADI [ ADI ]
