DS18B20-PAR 1-Wire Parasite-Power Digital Thermometer

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DS18B20-PARtransmitted least significant bit first. All three bytes MUST be written before the master issues a reset, orthe data may be corrupted.READ SCRATCHPAD [BEh]This command allows the master to read the contents of the scratchpad. The data transfer starts with theleast significant bit of byte 0 and continues through the scratchpad until the 9 th byte (byte 8 – CRC) isread. If only part of the scratchpad contents is required, the master may issue a reset to terminate readingat any time.COPY SCRATCHPAD [48h]This command copies the contents of the scratchpad T H , T L and configuration registers (bytes 2, 3 and 4)to EEPROM. Within 10 s (max) after this command is issued the master must enable a strong pullup onthe 1-Wire bus for at least 10 ms as described in the PARASITE POWER section.RECALL E 2 [B8h]This command recalls the alarm trigger values (T H and T L ) and configuration data from EEPROM andplaces the data in bytes 2, 3, and 4, respectively, in the scratchpad memory. The master device can issue“read time slots” (see the 1-WIRE BUS SYSTEM section) following the Recall E 2 command and theDS18B20-PAR will indicate the status of the recall by transmitting 0 while the recall is in progress and1 when the recall is done. The recall operation happens automatically at power-up, so valid data isavailable in the scratchpad as soon as power is applied to the device.DS18B20-PAR Function Command Set Table 4Command Description Protocol1-Wire Bus ActivityAfter Command is Issued NotesTEMPERATURE CONVERSION COMMANDSConvert T Initiates temperature44h None 1conversion.MEMORY COMMANDSRead Scratchpad Reads the entire scratchpad BEh DS18B20-PAR transmits up 2including the CRC byte.to 9 data bytes to master.Write Scratchpad Writes data into scratchpad 4Eh Master transmits 3 data 3bytes 2, 3, and 4 (T H , T L , andconfiguration registers).bytes to DS18B20-PAR.Copy Scratchpad Copies T H , T L , andconfiguration register data from48h None 1Recall E 2the scratchpad to EEPROM.Recalls T H , T L , andconfiguration register data fromEEPROM to the scratchpad.B8hDS18B20-PAR transmitsrecall status to master.NOTES:1. The master must enable a strong pullup on the 1-Wire bus during temperature conversions and copiesfrom the scratchpad to EEPROM. No other bus activity may take place during this time.2. The master can interrupt the transmission of data at any time by issuing a reset.3. All three bytes must be written before a reset is issued.10 of 19
ROM COMMANDS FLOW CHART Figure 10DS18B20-PARInitializationSequenceMASTER TXRESET PULSEDS18B20-PARTX PRESENCEPULSEMASTER TX ROMCOMMAND33hREAD ROMCOMMAND55hCChN F0hEChNN NMATCH ROMSEARCH ROMALARM SEARCHSKIP ROM NCOMMANDCOMMANDCOMMANDCOMMANDY Y Y Y YMASTER TXBIT 0DS18B20-PAR TXFAMILY CODE1 BYTEDS18B20-PAR TX BIT 0DS18B20-PAR TX BIT 0MASTER TX BIT 0DS18B20-PAR TX BIT 0DS18B20-PAR TX BIT 0MASTER TX BIT 0BIT 0MATCH?NNBIT 0MATCH?DEVICE(S)WITH ALARMFLAG SET?NDS18B20-PAR TXSERIAL NUMBER6 BYTESYYYDS18B20-PAR TXCRC BYTEMASTER TXBIT 1DS18B20-PAR TX BIT 1DS18B20-PAR TX BIT 1MASTER TX BIT 1BIT 1MATCH?NNBIT 1MATCH?YYDS18B20-PAR TX BIT 63MASTER TXBIT 63DS18B20-PAR TX BIT 63MASTER TX BIT 63BIT 63MATCH?NNBIT 63MATCH?YYMASTER TXFUNCTIONCOMMAND(FIGURE 11)11 of 19
Page 1: FEATURES Unique 1-Wire ® interface
Page 4 and 5: DS18B20-PARresolution, bits 1 and 0
Page 6 and 7: DS18B20-PAR MEMORY MAP Figure 6DS18
Page 8 and 9: DS18B20-PARHARDWARE CONFIGURATION F
Page 12 and 13: DS18B20-PAR FUNCTION COMMANDS FLOW
Page 14 and 15: DS18B20-PARThe DS18B20-PAR samples
Page 16 and 17: DS18B20-PARMASTER MODE DATA (LSB FI
Page 18 and 19: AC ELECTRICAL CHARACTERISTICSDS18B2

DS18B20-PAR 1-Wire Parasite-Power Digital Thermometer

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