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AT45DB321D Datasheet(PDF) 5 Page - List of Unclassifed Manufacturers |
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AT45DB321D Datasheet(HTML) 5 Page - List of Unclassifed Manufacturers |
5 / 52 page 5 AT45DB321D [DATASHEET] 3597T–DFLASH–11/2013 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 Table 13-1 on page 24 through Table 13-7 on page 27. 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 Section 22., Detailed Bit-level Read Waveform – RapidS Serial Interface Mode 0/Mode 3 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 fCAR1 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 fCAR1. 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. |
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