The CS pin must remain low during the loading of the opcode, the address bytes, and the read-
ing of data. When the end of a page in the main memory is reached during a Continuous Array
Read, the device will continue reading at the beginning of the next page with no delays incurred
during the page boundary crossover (the crossover from the end of one page to the beginning of
the next page). When the last bit in the main memory array has been read, the device will con-
tinue reading back at the beginning of the first page of memory. As with crossing over page
boundaries, no delays will be incurred when wrapping around from the end of the array to the
beginning of the array. A low-to-high transition on the CS pin will terminate the read operation
and tri-state the output pin (SO). The maximum SCK frequency allowable for the Continuous
Array Read is defined by the fCAR1 specification. The Continuous Array Read bypasses both
data buffers and leaves the contents of the buffers unchanged.
6.3
Continuous Array Read (Low Frequency Mode: 03H): Up to 33 MHz
This command can be used with the serial interface to read the main memory array sequentially
without a dummy byte up to maximum frequencies specified by fCAR2. To perform a continuous
read array with the page size set to 264 bytes, the CS must first be asserted then an opcode,
03H, must be clocked into the device followed by three address bytes (which comprise the 24-bit
page and byte address sequence). The first 11 bits (PA10 - PA0) of the 20-bit address sequence
specify which page of the main memory array to read, and the last 9 bits (BA8 - BA0) of the
20-bit address sequence specify the starting byte address within the page. To perform a contin-
uous read with the page size set to 256 bytes, the opcode, 03H, must be clocked into the device
followed by three address bytes (A18 - A0). Following the address bytes, additional clock pulses
on the SCK pin will result in data being output on the SO (serial output) pin.
The CS pin must remain low during the loading of the opcode, the address bytes, and the read-
ing of data. When the end of a page in the main memory is reached during a Continuous Array
Read, the device will continue reading at the beginning of the next page with no delays incurred
during the page boundary crossover (the crossover from the end of one page to the beginning of
the next page). When the last bit in the main memory array has been read, the device will con-
tinue reading back at the beginning of the first page of memory. As with crossing over page
boundaries, no delays will be incurred when wrapping around from the end of the array to the
beginning of the array. A low-to-high transition on the CS pin will terminate the read operation
and tri-state the output pin (SO). The Continuous Array Read bypasses both data buffers and
leaves the contents of the buffers unchanged.
6.4
Main Memory Page Read
A main memory page read allows the user to read data directly from any one of the 2,048 pages
in the main memory, bypassing both of the data buffers and leaving the contents of the buffers
unchanged. To start a page read from the DataFlash standard page size (264 bytes), an opcode
of D2H must be clocked into the device followed by three address bytes (which comprise the
24-bit page and byte address sequence) and 4 don’t care bytes. The first 11 bits (PA10 - PA0) of
the 20-bit address sequence specify the page in main memory to be read, and the last 9 bits
(BA8 - BA0) of the 20-bit address sequence specify the starting byte address within that page.
To start a page read from the binary page size (256 bytes), the opcode D2H must be
clocked into the device followed by three address bytes and 4 don’t care bytes. The first 11 bits
(A18 - A8) of the 19-bits sequence specify which page of the main memory array to read, and
the last 8 bits (A7 - A0) of the 19-bits address sequence specify the starting byte address within
the page. The don’t care bytes that follow the address bytes are sent to initialize the read opera-
tion. Following the don’t care bytes, additional pulses on SCK result in data being output on the
SO (serial output) pin. The CS pin must remain low during the loading of the opcode, the
address bytes, the don’t care bytes, and the reading of data. When the end of a page in main
6
AT45DB041D
3595L–DFLASH–4/08
ATMEL [ ATMEL ]
