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DS18B20 データシート(PDF) 18 Page - Dallas Semiconductor |
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DS18B20 データシート(HTML) 18 Page - Dallas Semiconductor |
18 / 22 page DS18B20 18 of 22 DS18B20 OPERATION EXAMPLE 1 In this example there are multiple DS18B20s on the bus and they are using parasite power. The bus master initiates a temperature conversion in a specific DS18B20 and then reads its scratchpad and recalculates the CRC to verify the data. MASTER MODE DATA (LSB FIRST) COMMENTS Tx Reset Master issues reset pulse. Rx Presence DS18B20s respond with presence pulse. Tx 55h Master issues Match ROM command. Tx 64-bit ROM code Master sends DS18B20 ROM code. Tx 44h Master issues Convert T command. Tx DQ line held high by strong pullup Master applies strong pullup to DQ for the duration of the conversion (tCONV). Tx Reset Master issues reset pulse. Rx Presence DS18B20s respond with presence pulse. Tx 55h Master issues Match ROM command. Tx 64-bit ROM code Master sends DS18B20 ROM code. Tx BEh Master issues Read Scratchpad command. Rx 9 data bytes Master reads entire scratchpad including CRC. The master then recalculates the CRC of the first eight data bytes from the scratchpad and compares the calculated CRC with the read CRC (byte 9). If they match, the master continues; if not, the read operation is repeated. DS18B20 OPERATION EXAMPLE 2 In this example there is only one DS18B20 on the bus and it is using parasite power. The master writes to the TH, TL, and configuration registers in the DS18B20 scratchpad and then reads the scratchpad and recalculates the CRC to verify the data. The master then copies the scratchpad contents to EEPROM. MASTER MODE DATA (LSB FIRST) COMMENTS Tx Reset Master issues reset pulse. Rx Presence DS18B20 responds with presence pulse. Tx CCh Master issues Skip ROM command. Tx 4Eh Master issues Write Scratchpad command. Tx 3 data bytes Master sends three data bytes to scratchpad (TH, TL, and config). Tx Reset Master issues reset pulse. Rx Presence DS18B20 responds with presence pulse. Tx CCh Master issues Skip ROM command. Tx BEh Master issues Read Scratchpad command. Rx 9 data bytes Master reads entire scratchpad including CRC. The master then recalculates the CRC of the first eight data bytes from the scratchpad and compares the calculated CRC with the read CRC (byte 9). If they match, the master continues; if not, the read operation is repeated. Tx Reset Master issues reset pulse. Rx Presence DS18B20 responds with presence pulse. Tx CCh Master issues Skip ROM command. Tx 48h Master issues Copy Scratchpad command. Tx DQ line held high by strong pullup Master applies strong pullup to DQ for at least 10ms while copy operation is in progress. |
同様の部品番号 - DS18B20 |
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同様の説明 - DS18B20 |
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