DS18S20-PAR+T&R Maxim Integrated Products, DS18S20-PAR+T&R Datasheet
DS18S20-PAR+T&R
Specifications of DS18S20-PAR+T&R
Related parts for DS18S20-PAR+T&R
DS18S20-PAR+T&R Summary of contents
Page 1
... Each DS18S20-PAR has a unique 64-bit identification code, which allows multiple DS18S20-PARs to function on the same 1–wire bus; thus simple to use one microprocessor to control many DS18S20-PARs distributed over a large area. Applications that can benefit from this feature include HVAC environmental controls, temperature monitoring systems inside buildings, equipment or machinery, and process monitoring and control systems ...
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... The control line requires a weak pullup resistor since all devices are linked to the bus via a 3-state or open-drain port (the DQ pin in the case of the DS18S20-PAR). In this bus system, the microprocessor (the master device) identifies and addresses devices on the bus using each device’s unique 64-bit code ...
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... Figure 1 shows the DS18S20-PAR’s parasite-power control circuitry, which “steals” power from the 1-Wire bus via the DQ pin when the bus is high. The stolen charge powers the DS18S20-PAR while the bus is high, and some of the charge is stored on the parasite power capacitor ( provide power when the bus is low ...
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... The master device can check the alarm flag status of all DS DS18S20-PARs on the bus by issuing an Alarm Search [ECh] command. Any DS18S20-PARs with a set alarm flag will respond to the command, ...
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... Data is written to bytes 2 and 3 of the scratchpad using the Write Scratchpad [4Eh] command; the data must be transmitted to the DS18S20-PAR starting with the least significant bit of byte 2. To verify data integrity, the scratchpad can be read (using the Read Scratchpad [BEh] command) after the data is written ...
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... The CRCs provide the bus master with a method of data validation when data is read from the DS18S20-PAR. To verify that data has been read correctly, the bus master must re-calculate the CRC from the received data and then compare this value to either the ROM code CRC (for ROM reads the scratchpad CRC (for scratchpad reads) ...
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... The 1-Wire port of the DS18S20-PAR (the DQ pin) is open drain with an internal circuit equivalent to that shown in Figure 8. The 1-Wire bus requires an external pullup resistor of approximately 5 kW; thus, the idle state for the 1- Wire bus is high ...
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... It is very important to follow the transaction sequence every time the DS18S20-PAR is accessed, as the DS18S20-PAR will not respond if any steps in the sequence are missing or out of order. Exceptions to this rule are the Search ROM [F0h] and Alarm Search [ECh] commands. After issuing either of these ROM commands, the master must return to Step 1 in the sequence ...
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... SIGNALING section for an explanation of alarm flag operation. DS18S20-PAR FUNCTION COMMANDS After the bus master has used a ROM command to address the DS18S20-PAR with which it wishes to communicate, the master can issue one of the DS18S20-PAR function commands. These commands allow the master to write to and read from the DS18S20-PAR’s scratchpad memory, initiate temperature conversions and determine the power supply mode ...
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... DS18S20-PAR FUNCTION COMMAND SET Table 4 Command TEMPERATURE CONVERSION COMMANDS Convert T Initiates temperature conversion. Read Scratchpad Reads the entire scratchpad including the CRC byte. Write Scratchpad Writes data into scratchpad bytes 2 and 3 (T Copy Scratchpad Copies T scratchpad to EEPROM. 2 Recalls T Recall E EEPROM to the scratchpad. ...
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... BIT 0 BIT 0 MATCH? MATCH DS18S20-PAR T BIT 1 X MASTER T X DS18S20-PAR T BIT 1 X BIT 1 MASTER T BIT BIT 1 BIT 1 MATCH? MATCH DS18S20-PAR T BIT 63 X MASTER T DS18S20-PAR T BIT BIT 63 MASTER T BIT BIT 63 BIT 63 MATCH? MATCH MASTER T X FUNCTION COMMAND (FIGURE 10 CCh ECh N SKIP ROM ...
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... DS18S20-PAR FUNCTION COMMANDS FLOW CHART Figure 10 MASTER T X FUNCTION COMMAND N B8h 2 RECALL MASTER BEGINS DATA 2 RECALL FROM E DEVICE BUSY RECALLING DATA ? Y MASTER R “0s” X 44h N CONVERT TEMPERATURE ? Y MASTER ENABLES STRONG PULLUP ON DQ DS18S20-PAR CONVERTS TEMPERATURE MASTER DISABLES STRONG PULLUP BEh N READ ...
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... There are two types of write time slots: “Write 1” time slots and “Write 0” time slots. The bus master uses a Write 1 time slot to write a logic 1 to the DS18S20-PAR and a Write 0 time slot to write a logic 0 to the DS18S20-PAR. All write time slots must be a minimum duration with a minimum recovery time between individual write slots ...
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... The DS18S20-PAR samples the 1-Wire bus during a window that lasts from after the master initiates the write time slot. If the bus is high during the sampling window written to the DS18S20-PAR. If the line is low written to the DS18S20-PAR. READ/WRITE TIME SLOT TIMING DIAGRAM Figure 12 ...
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... Output data from the DS18S20-PAR is valid for 15 ms after the falling edge that initiated the read time slot. Therefore, the master must release the bus and then sample the bus state within 15 ms from the start of the slot ...
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... DS18S20-PAR OPERATION EXAMPLE 1 In this example there is only one DS18S20-PAR on the bus. The master writes to the T in the DS18S20-PAR 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 ...
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... DS18S20-PAR OPERATION EXAMPLE 3 In this example there is only one DS18S20-PAR on the bus. The bus master initiates a temperature conversion then reads the DS18S20-PAR scratchpad and calculates a higher resolution result using the data from the temperature, COUNT REMAIN and COUNT PER °C registers. ...
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... The Pullup Supply Voltage specification assumes that the pullup device (resistor or transistor) is ideal, and therefore the high level of the pullup is equal to V DS18S20-PAR, the actual supply rail for the strong pullup transistor must include margin for the voltage drop across the transistor when it is turned on; thus ...
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... Start Convert T or SPON Copy Scratchpad Command Issued t SLOT t REC r LOW0 t LOW1 t RDV t RSTH t RSTL t PDHIGH t PDLOW C IN/OUT DS18S20-PAR Typical Error Curve +3s Error Reference Temp (° =3.0V to 5.5V) PU MIN TYP MAX UNITS NOTES 750 ms 10 µs 60 120 µs 1 µs 60 120 µs ...
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TIMING DIAGRAMS Figure ...