DS1820 Dallas Semiconductor, DS1820 Datasheet
DS1820
Specifications of DS1820
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DS1820 Summary of contents
Page 1
... The DS1820 Digital Thermometer provides 9–bit tem- perature readings which indicate the temperature of the device. Information is sent to/from the DS1820 over a 1–Wire interface, so that only one wire (and ground) needs to be connected from a central microprocessor to a DS1820. Power for reading, writing, and performing temperature conversions can be derived from the data line itself with no need for an external power source ...
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... DS1820S (16–pin SSOP): All pins not specified in this table are not to be connected. OVERVIEW The block diagram of Figure 1 shows the major compo- nents of the DS1820. The DS1820 has three main data components: 1) 64–bit lasered ROM, 2) temperature sensor, and 3) nonvolatile temperature alarm triggers TH and TL. The device derives its power from the 1– ...
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... ROM may be read in absence of normal power. In order for the DS1820 to be able to perform accurate temperature conversions, sufficient power must be pro- vided over the I/O line when a temperature conversion is taking place ...
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... The DS1820 can measure temperature over the range of – +125 C in 0.5 C increments. For Fahrenheit usage, a lookup table or conversion factor must be used. Note that temperature is represented in the DS1820 in 1 terms LSB, yielding the following 9–bit format: ...
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... This flag is updated with every temperature measure- ment. As long as the alarm flag is set, the DS1820 will respond to the alarm search command. This allows many DS1820s to be connected in parallel doing simul- taneous temperature measurements. If somewhere the ...
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... CRC value stored in the 64–bit ROM portion of the DS1820 (for ROM reads) or the 8–bit CRC value com- puted within the DS1820 (which is read as a ninth byte when the scratchpad is read). The comparison of CRC values and decision to continue with an operation are determined entirely by the bus master ...
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... FUNCTION COMMAND 55h F0h N SEARCH ROM COMMAND Y Y BIT 0 X DS1820 T BIT 0 X DS1820 T BIT 0 X MASTER T BIT BIT 0 BIT 0 MATCH DS1820 T BIT 1 X DS1820 T BIT 1 X BIT 1 X MASTER T BIT BIT 1 BIT 1 MATCH DS1820 T BIT 63 X BIT 63 X DS1820 T BIT 63 X ...
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... DS1820 1–WIRE CRC CODE Figure 7 (MSB) MEMORY The DS1820’s memory is organized as shown in Figure 8. The memory consists of a scratchpad RAM and a nonvolatile, electrically erasable (E stores the high and low temperature triggers TH and TL. The scratchpad helps insure data integrity when com- municating over the 1–Wire bus. Data is first written to the scratchpad where it can be read back ...
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... The presence pulse lets the bus master know that the DS1820 is on the bus and is ready to operate. For more details, see the “1–Wire Signaling” section. ROM FUNCTION COMMANDS Once the bus master has detected a presence, it can issue one of the five ROM function commands ...
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... DS1820’s 8–bit family code, unique 48–bit serial num- ber, and 8–bit CRC. This command can only be used if there is a single DS1820 on the bus. If more than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same time (open drain will produce a wired AND result) ...
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... The initialization sequence required to begin any com- munication with the DS1820 is shown in Figure 11. A reset pulse followed by a presence pulse indicates the DS1820 is ready to send or receive data given the cor- rect ROM command and memory function command. The bus master transmits (TX) a reset pulse (a low sig- nal for a minimum of 480 s) ...
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... DS1820 I/O pin, the DS1820 waits 15–60 s and then transmits the presence pulse (a low signal for 60–240 s). MEMORY COMMAND FUNCTIONS The following command protocols are summarized in Table 2, and by the flowchart of Figure 10. 021497 12/27 Write Scratchpad [4Eh] This command writes to the scratchpad of the DS1820, starting at address 2 ...
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... X TO SCRATCHPAD Y MASTER T RESET ADDRESS = DS1820 INCREMENTS ADDRESS N MASTER T RESET DS1820 T X PRESENCE PULSE BEh N READ SCRATCHPAD ? Y DS1820 SETS ADDRESS COUNTER TO 0 MASTER R DATA X FROM SCRATCHPAD Y MASTER T RESET ADDRESS = DS1820 INCREMENTS ADDRESS MASTER R 8–BIT X CRC OF DATA Y MASTER T RESET MASTER R “1s” ...
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... STRONG PULLUP DS1820 BEGINS CONVERSION Y Y MASTER R “0”s X 44h N CONVERT TEMPERATURE ? Y Y PARASITE POWER ? Y MASTER T X RESET ? N DEVICE BUSY N Y CONVERTING TEMPERATURE ? MASTER MASTER R “1” MASTER ENABLES STRONG PULL–UP DS1820 CONVERTS TEMPERATURE MASTER DISABLES STRONG PULL–UP “0”s ...
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... MEMORY FUNCTIONS FLOW CHART Figure 10 (cont’d) B8h RECALL DS1820 RECALLS 2 FROM E PROM MASTER T RESET X ? DEVICE N BUSY CONVERTING TEMPERATURE ? MASTER MASTER R “1” POWER SUPPLY Y PARASITE N Y POWERED MASTER R “1” “0”s X B4h N READ ? Y Y MASTER T RESET MASTER R “0”s ...
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... After receiving the Copy Scratchpad protocol, if the part does not receive power from the V for the DS1820 must be held high for at least provide power during the copy process. As such, no other activity may take place on the 1–Wire bus for at least this period after a Copy Scratchpad command has been issued ...
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... DS1820 will remain idle. If the bus master issues read time slots following this com- mand, the DS1820 will output “0” on the bus as long busy making a temperature conversion; it will return a “1” when the temperature conversion is complete. If par- ...
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... DS1820 SAMPLES MIN TYP s< t < REC MASTER READ “1” SLOT Ç Ç Ç Ç Ç Ç Ç Ç Ç >1 s MASTER SAMPLES 15 s DS1820 active low Resistor pull–up MAX 3 s ...
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... RECOMMENDED MASTER READ “1” TIMING Figure 1–WIRE BUS GND INIT RC SMALL SMALL LINE TYPE LEGEND MASTER Bus master active low Both bus master and DS1820 active low DS1820 V OF MASTER IH MASTER SAMPLES MASTER SAMPLES DS1820 active low Resistor pull–up 021497 19/27 ...
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... DS1820 Related Application Notes The following Application Notes can be applied to the DS1820. These notes can be obtained from the Dallas Application Note 27: “Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor Touch Memory Product” Application Note 55: “Extending the Contact Range of Touch Memories” ...
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... TX RX Reset Reset pulse (480–960 s). Presence Presence pulse. 55h Issue “Match ROM” command. Issue address for DS1820. 44h Issue “Convert T” command. I/O line is held high for at least 500 ms by bus master to allow conversion to complete. Reset Reset pulse. Presence Presence pulse ...
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... DS1820 MEMORY FUNCTION EXAMPLE Table 4 Example: Bus Master writes memory (parasite power and only one DS1820 assumed). MASTER MODE DATA (LSB FIRST <2 data bytes> <9 data bytes> 021497 22/27 Reset Reset pulse. Presence Presence pulse. CCh Skip ROM command. 4Eh Write Scratchpad command ...
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... MEMORY FUNCTION EXAMPLE Table 5 Example: Temperature conversion and interpolation (external power supply and only one DS1820 assumed). MASTER MODE DATA (LSB FIRST <1 data byte> <9 data bytes> – Reset Reset pulse. Presence Presence pulse. CCh Skip ROM command. 44h Convert T command. ...
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... DS1820 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature * This is a stress rating 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 ...
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... LOW1 t RDV t 480 RSTH t 480 RSTL t 15 PDHIGH t 60 PDLOW C IN/OUT DD V 5.5V SLOT (– +125 C; V =3.6V to 5.5V) DD MAX UNITS 500 ms 120 s s 120 4800 240 3.4 volts memory. Writing to E memory con- START OF NEXT CYCLE DS1820 NOTES 021497 25/27 ...
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... DS1820 1–WIRE WRITE ZERO TIME SLOT t REC 1–WIRE READ ZERO TIME SLOT 1–WIRE RESET PULSE RESET PULSE FROM HOST 1–WIRE PRESENCE DETECT 021497 26/27 t SLOT t LOW0 t SLOT t REC t RDV t RSTL START OF NEXT CYCLE START OF NEXT CYCLE t RSTH PRESENCE DETECT t PDHIGH t PDLOW ...
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... TYPICAL PERFORMANCE CURVE –55 –35 –15 LOWER LIMIT SPECIFICATION DS1820 DIGITAL TERMOMETER AND THERMOSTAT TEMPERATURE READING ERROR –1 –2 –3 TEMPERATURE (deg. C) SPECIFICATION DS1820 UPPER LIMIT 105 125 TYPICAL ERROR 021497 27/27 ...