AT45DB081D
5. Device Operation
The device operation is controlled by instructions from the host processor. The list of instructions
and their associated opcodes are contained in Table 15-1 on page 28 through Table 15-7 on
page 31. A valid instruction starts with the falling edge of CS followed by the appropriate 8-bit
opcode and the desired buffer or main memory address location. While the CS pin is low, tog-
gling the SCK pin controls the loading of the opcode and the desired buffer or main memory
address location through the SI (serial input) pin. All instructions, addresses, and data are trans-
ferred with the most significant bit (MSB) first.
Buffer addressing for the DataFlash standard page size (264 bytes) is referenced in the
datasheet using the terminology BFA8 - BFA0 to denote the 9 address bits required to designate
a byte address within a buffer. Main memory addressing is referenced using the terminology
PA11 - PA0 and BA8 - BA0, where PA11 - PA0 denotes the 12 address bits required to desig-
nate a page address and BA8 - BA0 denotes the 9 address bits required to designate a byte
address within the page.
For “Power of 2” binary page size (256 bytes) the Buffer addressing is referenced in the
datasheet using the conventional terminology BFA7 - BFA0 to denote the 8 address bits
required to designate a byte address within a buffer. Main memory addressing is referenced
using the terminology A19 - A0, where A19 - A8 denotes the 12 address bits required to desig-
nate a page address and A7 - A0 denotes the 8 address bits required to designate a byte
address within a page.
6. Read Commands
By specifying the appropriate opcode, data can be read from the main memory or from either
one of the two SRAM data buffers. The DataFlash supports RapidS protocols for Mode 0 and
Mode 3. Please refer to the “Detailed Bit-level Read Timing” diagrams in this datasheet for
details on the clock cycle sequences for each mode.
6.1
Continuous Array Read (Legacy Command: E8H): Up to 66 MHz
By supplying an initial starting address for the main memory array, the Continuous Array Read
command can be utilized to sequentially read a continuous stream of data from the device by
simply providing a clock signal; no additional addressing information or control signals need to
be provided. The DataFlash incorporates an internal address counter that will automatically
increment on every clock cycle, allowing one continuous read operation without the need of
additional address sequences. To perform a continuous read from the DataFlash standard page
size (264 bytes), an opcode of E8H 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 12 bits (PA11 - PA0) of the 21-bit address sequence specify which page of the main mem-
ory array to read, and the last 9 bits (BA8 - BA0) of the 21-bit address sequence specify the
starting byte address within the page. To perform a continuous read from the binary page size
(256 bytes), the opcode (E8H) must be clocked into the device followed by three address bytes
and 4 don’t care bytes. The first 12 bits (A19 - A8) of the 20-bits sequence specify which page of
the main memory array to read, and the last 8 bits (A7 - A0) of the 20-bits address sequence
specify the starting byte address within the page. The don’t care bytes that follow the address
bytes are needed to initialize the read operation. Following the don’t care 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, the don’t care
bytes, and the reading of data. When the end of a page in main memory is reached during a
5
3596L–DFLASH–04/09
ATMEL [ ATMEL ]
