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전자부품 데이터시트 검색엔진 |
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전자부품 데이터시트 검색엔진 |
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AT45DB021D 데이터시트(PDF) 6 Page - ATMEL Corporation |
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AT45DB021D 데이터시트(HTML) 6 Page - ATMEL Corporation |
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6 / 54 page  6 3638I–DFLASH–04/09 AT45DB021D 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 the data buffer and leaves the contents of the buffer 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 10 bits (PA9 - PA0) of the 19-bit address sequence specify which page of the main memory array to read, and the last 9 bits (BA8 - BA0) of the 19-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 (A17 - 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 the data buffer and leaves the contents of the buffer 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 the data buffer and leaving the contents of the buffer 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 10 bits (PA9 - PA0) of the 19-bit address sequence specify the page in main memory to be read, and the last 9 bits (BA8 - BA0) of the 19-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 10 bits (A17 - A8) of the 18-bit sequence specify which page of the main memory array to read, and the last 8 bits (A7 - A0) of the 18-bit 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 operation. 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 memory is |
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