3.
Device Operation
The device operation is controlled by instructions from the host processor. The list of instructions and their associated opcodes
are contained in
through
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,
toggling 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 transferred with the most-significant bit (msb) first.
Buffer addressing for the standard DataFlash page size (528 bytes) is referenced in the datasheet using the terminology BFA9
- BFA0 to denote the ten address bits required to designate a byte address within a buffer. Main memory addressing is
referenced using the terminology PA12 - PA0 and BA9 - BA0, where PA12 - PA0 denotes the 13 address bits required to
designate a page address and BA9 - BA0 denotes the ten address bits required to designate a byte address within the page.
For a “power of two” binary page size (512 bytes), the buffer addressing is referenced in the datasheet using the conventional
terminology BFA8 - BFA0 to denote the nine address bits required to designate a byte address within a buffer. Main memory
addressing is referenced using the terminology A21 - A0, where A21 - A9 denotes the 13 address bits required to designate a
page address and A8 - A0 denotes the nine address bits required to designate a byte address within a page.
4.
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 device supports RapidS protocols for Mode 0 and Mode 3. Please refer to
diagrams in this datasheet for details on the clock cycle sequences
for each mode.
4.1
Continuous Array Read (Legacy Command: E8H): Up to 66MHz
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 device 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 standard DataFlash page size (528 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 four
“don’t care” bytes. The first 13 bits (PA12 - PA0) of the 23-bit address sequence specify which page of the main memory array
to read, and the last 10 bits (BA9 - BA0) of the 23-bit address sequence specify the starting byte address within the page. To
perform a continuous read from the binary page size (512-bytes), the opcode (E8H) must be clocked into the device followed by
three address bytes and four don’t care bytes. The first 13 bits (A21 - A9) of the 22-bit sequence specify which page of the main
memory array to read, and the last 9 bits (A8 - A0) of the 22-bit 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 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 continue
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 f
CAR1
specification. The continuous array read bypasses
both data buffers and leaves the contents of the buffers unchanged.
4.2
Continuous Array Read (High Frequency Mode: 0BH): Up to 66MHz
This command can be used with the serial interface to read the main memory array sequentially in high-speed mode for any
clock frequency up to the maximum specified by f
CAR1
. To perform a continuous read array with the page size set to 528 bytes,
CS must first be asserted, and then a 0BH opcode must be clocked into the device, followed by three address bytes and a
dummy byte. The first 13 bits (PA12 - PA0) of the 23-bit address sequence specify which page of the main memory array to
read, and the last 10 bits (BA9 - BA0) of the 23-bit address sequence specify the starting byte address within the page. To
perform a continuous read with the page size set to 512 bytes, the 0BH opcode must be clocked into the device, followed by
three address bytes (A21 - A0) and a dummy byte. Following the dummy byte, additional clock pulses on the SCK pin will result
in data being output on the SO (serial output) pin.
Atmel AT45DB321D
3597Q–DFLASH–6/11
5
ATMEL [ ATMEL CORPORATION ]
