Instruction Manual

ManualsBrandsRainbow Electronics ManualsControl panelDS18S20

1 of 21 043001

FEATURES

• Unique 1-wire interface requires only one

port pin for communication

• Each device has a unique 64-bit serial code

stored in an on-board ROM

• Multi-drop capability simplifies distributed

temperature sensing applications

• Requires no external components

• Can be powered from data line. Power supply

range is 3.0V to 5.5V

• Measures temperatures from –55°C to

+125°C (–67°F to +257°F)

• ±0.5°C accuracy from –10°C to +85°C

• 9-bit thermometer resolution

• Converts temperature in 750 ms (max.)

• User-definable nonvolatile alarm settings

• Alarm search command identifies and

addresses devices whose temperature is

outside of programmed limits (temperature

alarm condition)

• Applications include thermostatic controls,

industrial systems, consumer products,

thermometers, or any thermally sensitive

system

PIN ASSIGNMENT

PIN DESCRIPTION

GND - Ground

DQ - Data In/Out

- Power Supply Voltage

NC - No Connect

DESCRIPTION

The DS18S20 Digital Thermometer provides 9–bit centigrade temperature measurements and has an

alarm function with nonvolatile user-programmable upper and lower trigger points. The DS18S20

communicates over a 1-wire bus that by definition requires only one data line (and ground) for

communication with a central microprocessor. It has an operating temperature range of –55°C to +125°C

and is accurate to ±0.5°C over the range of –10°C to +85°C. In addition, the DS18S20 can derive power

directly from the data line (“parasite power”), eliminating the need for an external power supply.

Each DS18S20 has a unique 64-bit serial code, which allows multiple DS18S20s to function on the same

1–wire bus; thus, it is simple to use one microprocessor to control many DS18S20s 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.

DS18S20

High Precision

1-Wire

Digital Thermomete

www.dalsemi.com

8-pin 150-mil SOIC

(DS18S20Z)

TO-92

(

DS18S20

)

(

BOTTOM VIEW

)

2 3

DALLAS

DS1820

GND

2 3

GND

DS1820

Summary of content (21 pages)

PAGE 1
DS18S20 High Precision ® 1-Wire Digital Thermometer www.dalsemi.com • • • • • • • • • • • Unique 1-wire interface requires only one port pin for communication Each device has a unique 64-bit serial code stored in an on-board ROM Multi-drop capability simplifies distributed temperature sensing applications Requires no external components Can be powered from data line. Power supply range is 3.0V to 5.5V Measures temperatures from –55°C to +125°C (–67°F to +257°F) ±0.
PAGE 2
DS18S20 DETAILED PIN DESCRIPTIONS Table 1 8-PIN SOIC* TO-92 SYMBOL DESCRIPTION 5 1 GND Ground. 4 2 DQ Data Input/Output pin. Open-drain 1-wire interface pin. Also provides power to the device when used in parasite power mode (see “Parasite Power” section.) 3 3 VDD Optional VDD pin. VDD must be grounded for operation in parasite power mode. *All pins not specified in this table are “No Connect” pins. OVERVIEW Figure 1 shows a block diagram of the DS18S20, and pin descriptions are given in Table 1.
PAGE 3
DS18S20 OPERATION – MEASURING TEMPERATURE The core functionality of the DS18S20 is its direct-to-digital temperature sensor. The temperature sensor output has 9-bit resolution, which corresponds to 0.5°C steps. The DS18S20 powers-up in a low-power idle state; to initiate a temperature measurement and A-to-D conversion, the master must issue a Convert T [44h] command.
PAGE 4
DS18S20 OPERATION – ALARM SIGNALING After the DS18S20 performs a temperature conversion, the temperature value is compared to the userdefined two’s complement alarm trigger values stored in the 1-byte TH and TL registers (see Figure 3). The sign bit (S) indicates if the value is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. The TH and TL registers are nonvolatile (EEPROM) so they will retain data when the device is powered down.
PAGE 5
DS18S20 The use of parasite power is not recommended for temperatures above 100°C since the DS18S20 may not be able to sustain communications due to the higher leakage currents that can exist at these temperatures. For applications in which such temperatures are likely, it is strongly recommended that the DS18S20 be powered by an external power supply. In some situations the bus master may not know whether the DS18S20s on the bus are parasite powered or powered by external supplies.
PAGE 6
DS18S20 MEMORY The DS18S20’s memory is organized as shown in Figure 7. The memory consists of an SRAM scratchpad with nonvolatile EEPROM storage for the high and low alarm trigger registers (TH and TL). Note that if the DS18S20 alarm function is not used, the TH and TL registers can serve as general-purpose memory. All memory commands are described in detail in the DS18S20 FUNCTION COMMANDS section. Byte 0 and byte 1 of the scratchpad contain the LSB and the MSB of the temperature register, respectively.
PAGE 7
DS18S20 CRC GENERATION CRC bytes are provided as part of the DS18S20’s 64-bit ROM code and in the 9th byte of the scratchpad memory. The ROM code CRC is calculated from the first 56 bits of the ROM code and is contained in the most significant byte of the ROM. The scratchpad CRC is calculated from the data stored in the scratchpad, and therefore it changes when the data in the scratchpad changes. The CRCs provide the bus master with a method of data validation when data is read from the DS18S20.
PAGE 8
DS18S20 1-WIRE BUS SYSTEM The 1-wire bus system uses a single bus master to control one or more slave devices. The DS18S20 is always a slave. When there is only one slave on the bus, the system is referred to as a “single-drop” system; the system is “multi-drop” if there are multiple slaves on the bus. All data and commands are transmitted least significant bit first over the 1-wire bus.
PAGE 9
DS18S20 INITIALIZATION All transactions on the 1-wire bus begin with an initialization sequence. The initialization sequence consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the slave(s). The presence pulse lets the bus master know that slave devices (such as the DS18S20) are on the bus and are ready to operate. Timing for the reset and presence pulses is detailed in the 1-WIRE SIGNALING section.
PAGE 10
DS18S20 every Alarm Search cycle (i.e., Alarm Search command followed by data exchange), the bus master must return to Step 1 (Initialization) in the transaction sequence. Refer to the OPERATION – ALARM SIGNALING section for an explanation of alarm flag operation. DS18S20 FUNCTION COMMANDS After the bus master has used a ROM command to address the DS18S20 with which it wishes to communicate, the master can issue one of the DS18S20 function commands.
PAGE 11
DS18S20 DS18S20 FUNCTION COMMAND SET Table 4 1-Wire Bus Activity Command Description Protocol After Command is Issued TEMPERATURE CONVERSION COMMANDS Convert T Initiates temperature 44h DS18S20 transmits conversion conversion. status to master (not applicable for parasite-powered DS18S20s). MEMORY COMMANDS Read Scratchpad Reads the entire scratchpad BEh DS18S20 transmits up to 9 data including the CRC byte. bytes to master.
PAGE 12
DS18S20 1-WIRE SIGNALING The DS18S20 uses a strict 1-wire communication protocol to insure data integrity. Several signal types are defined by this protocol: reset pulse, presence pulse, write 0, write 1, read 0, and read 1. All of these signals, with the exception of the presence pulse, are initiated by the bus master.
PAGE 13
DS18S20 READ TIME SLOTS The DS18S20 can only transmit data to the master when the master issues read time slots. Therefore, the master must generate read time slots immediately after issuing a Read Scratchpad [BEh] or Read Power Supply [B4h] command, so that the DS18S20 can provide the requested data. In addition, the master can generate read time slots after issuing Convert T [44h] or Recall E2 [B8h] commands to find out the status of the operation as explained in the DS18S20 FUNCTION COMMAND section.
PAGE 14
DS18S20 DETAILED MASTER READ 1 TIMING Figure 12 VPU VIH of Master 1-WIRE BUS GND TINT > 1 µs TRC Master samples 15 µs RECOMMENDED MASTER READ 1 TIMING Figure 13 VPU VIH of Master 1-WIRE BUS GND Master samples TINT = TRC = small small 15 µs LINE TYPE LEGEND Bus master pulling low Resistor pullup 14 of 21
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DS18S20 ROM COMMANDS FLOW CHART Figure 14 Initialization Sequence MASTER TX RESET PULSE DS18S20 TX PRESENCE PULSE MASTER TX ROM COMMAND 33h READ ROM COMMAND Y N 55h MATCH ROM COMMAND F0h SEARCH ROM COMMAND N Y Y N ECh ALARM SEARCH COMMAND N Y Y MASTER TX BIT 0 DS18S20 TX BIT 0 DS18S20 TX BIT 0 DS18S20 TX BIT 0 DS18S20 TX BIT 0 MASTER TX BIT 0 MASTER TX BIT 0 BIT 0 MATCH? DEVICE(S) WITH ALARM FLAG SET? DS18S20 TX FAMILY CODE 1 BYTE N BIT 0 MATCH? DS18S20 TX SERIAL NUMBER 6 BYTES
PAGE 16
DS18S20 DS18S20 FUNCTION COMMANDS FLOW CHART Figure 15 44h CONVERT TEMPERATURE ? MASTER TX FUNCTION COMMAND 48h COPY SCRATCHPAD ? N Y Y N PARASITE POWER ? DS18S20 BEGINS CONVERSION Y N DATA COPIED FROM SCRATCHPAD TO EEPROM B4h READ POWER SUPPLY ? PARASITE POWERED ? N MASTER DISABLES STRONG PULLUP Y MASTER RX “0s” MASTER RX “1s” N B8h RECALL E2 ? MASTER RX “1s” BEh READ SCRATCHPAD ? N Y Y N COPY IN PROGRESS ? MASTER DISABLES STRONG PULLUP MASTER RX “0s” Y MASTER ENABLES STRONG
PAGE 17
DS18S20 DS18S20 OPERATION EXAMPLE 1 In this example there are multiple DS18S20s on the bus and they are using parasite power. The bus master initiates a temperature conversion in a specific DS18S20 and then reads its scratchpad and recalculates the CRC to verify the data. MASTER MODE TX RX TX TX TX TX TX RX TX TX TX RX DATA (LSB FIRST) Reset Presence 55h 64-bit ROM code 44h DQ line held high by strong pullup Reset Presence 55h 64-bit ROM code BEh 9 data bytes COMMENTS Master issues reset pulse.
PAGE 18
DS18S20 DS18S20 OPERATION EXAMPLE 3 In this example there is only one DS18S20 on the bus and it is using parasite power. The bus master initiates a temperature conversion then reads the DS18S20 scratchpad and calculates a higher resolution result using the data from the temperature, COUNT REMAIN and COUNT PER °C registers.
PAGE 19
DS18S20 ABSOLUTE MAXIMUM RATINGS* Voltage on any pin relative to ground Operating temperature Storage temperature Soldering temperature –0.5V to +6.0V –55°C to +125°C –55°C to +125°C See J-STD-020A Specification *These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
PAGE 20
DS18S20 AC ELECTRICAL CHARACTERISTICS: NV MEMORY (-55°C to +100°C; VDD=3.0V to 5.
PAGE 21
DS18S20 TIMING DIAGRAMS Figure 17 21 of 21