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Dallas DS1820, Инструкция

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DS1820

021497 26/27

1–WIRE WRITE ZERO TIME SLOT

START OF NEXT CYCLE

t

REC

t

SLOT

t

LOW0

1–WIRE READ ZERO TIME SLOT

START OF NEXT CYCLE

t

REC

t

SLOT

t

RDV

1–WIRE RESET PULSE

RESET PULSE FROM HOST

PRESENCE DETECT

1–WIRE PRESENCE DETECT

t

RSTL

t

RSTH

t

PDHIGH

t

PDLOW

Содержание DS1820

Страница 1: ...roducts thermometers or any thermally sensitive system PIN ASSIGNMENT 3 2 1 DALLAS DS2434 GND DQ VDD DALLAS DS1820 3 2 1 DS1820S 16 PIN SSOP DS1820 PR35 PACKAGE 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9...

Страница 2: ...ive ROM function commands 1 Read ROM 2 Match ROM 3 Search ROM 4 Skip ROM or 5 Alarm Search These commands operate on the 64 bit lasered ROM portion of each device and can single out a specific device...

Страница 3: ...DS1820 is through the use of an external power supply tied to the VDD pin as shown in Figure 3 The advantage to this is thatthe strong pull up is not required on the I O line and the bus master need n...

Страница 4: ...unter to go through for each incremental degree in temperature To obtain the desired resolution therefore both the value of the counter and the number of counts per degree C the value of the slope acc...

Страница 5: ...med a temperature conver sion the temperature value is compared to the trigger values stored in TH and TL Since these registers are 8 bit only the 0 5 C bit is ignored for comparison The most signific...

Страница 6: ...shown above and pro vides this value to the bus master to validate the transfer of data bytes In each case where a CRC is used for data transfer validation the bus master must calculate a CRC value us...

Страница 7: ...TES DS1820 TX CRC BYTE N N N Y Y Y N N Y N N Y Y Y DS1820 TX BIT 0 DS1820 TX BIT 0 DS1820 TX BIT 1 DS1820 TX BIT 1 DS1820 TX BIT 63 DS1820 TX BIT 63 MASTER TX BIT 1 MASTER TX BIT 0 MASTER TX BIT 0 MAS...

Страница 8: ...s contain the measured temperature information The third and fourth bytes are volatile copies of TH and TL and are refreshed with every pow er on reset The next two bytes are not used upon reading bac...

Страница 9: ...forthe 1 Wirebusishigh Ifforanyreason a transaction needs to be suspended the bus MUST be left in the idle state if the transaction is to resume Infinite recovery time can occur between bits so long...

Страница 10: ...ue For alarming the trigger values stored in EEPROM are taken into account If an alarm condition exists and the TH or TL settings are changed another temperature conversion should be done to validate...

Страница 11: ...ects ROM1 and ROM4 for the remainder of this search pass leaving only ROM2 and ROM3 coupled to the system 15 The bus master executes two read time slots and receives two zeros 16 The bus master writes...

Страница 12: ...NS The following command protocols are summarized in Table 2 and by the flowchart of Figure 10 Write Scratchpad 4Eh This command writes to the scratchpad of the DS1820 starting at address 2 The next t...

Страница 13: ...STER TX DATA BYTE TO SCRATCHPAD MASTER TX RESET ADDRESS 3 DS1820 INCREMENTS ADDRESS MASTER TX RESET BEh READ SCRATCHPAD DS1820 SETS ADDRESS COUNTER TO 0 MASTER RX DATA FROM SCRATCHPAD MASTER TX RESET...

Страница 14: ...UP N N Y Y Y DS1820 CONVERTS TEMPERATURE MASTER DISABLES STRONG PULL UP DS1820 BEGINS CONVERSION MASTER TX RESET DEVICE BUSY CONVERTING TEMPERATURE MASTER RX 1 s MASTER RX 0 s MASTER TX RESET NONVOLA...

Страница 15: ...10 cont d B8h RECALL E2 DS1820 RECALLS FROM E2 PROM MASTER TX RESET B4h READ POWER SUPPLY N N Y Y MASTER TX RESET N Y Y PARASITE POWERED MASTER RX 0 s N Y MASTER RX 1 s MASTER TX RESET N Y DEVICE BUSY...

Страница 16: ...pies scratchpad into nonvolatile memory addresses 2 and 3 only 48h read copy status 2 Recall E2 Recalls values stored in nonvolatile memory into scratchpad tempera ture triggers B8h read temperature b...

Страница 17: ...ode 0 parasite power 1 external power supply provided READ WRITE TIME SLOTS DS1820 data is read and written through the use of time slots to manipulate bits and a command word to specify the transacti...

Страница 18: ...s 30 s 15 s 30 s DS1820 SAMPLES MIN TYP MAX MASTER READ 0 SLOT MASTER READ 1 SLOT 15 s 1 s MASTER SAMPLES 15 s 15 s DS1820 SAMPLES MIN TYP MAX 1 s tREC 1 s tREC 15 s 30 s 15 s MASTER SAMPLES LINE TYPE...

Страница 19: ...1 S TRC MASTER SAMPLES 1 WIRE BUS VIH OF MASTER RECOMMENDED MASTER READ 1 TIMING Figure 14 VCC GND 15 s MASTER SAMPLES TRC SMALL TINIT SMALL 1 WIRE BUS VIH OF MASTER LINE TYPE LEGEND Bus master activ...

Страница 20: ...miconductor Touch Memory Product Application Note 55 Extending the Contact Range of Touch Memories Application Note 74 Reading and Writing Touch Memories via Serial Interfaces Application Note 104 Min...

Страница 21: ...HIGH I O line is held high for at least 500 ms by bus master to allow conversion to complete TX Reset Reset pulse RX Presence Presence pulse TX 55h Issue Match ROM command TX 64 bit ROM code Issue add...

Страница 22: ...lse TX CCh Skip ROM command TX BEh Read Scratchpad command RX 9 data bytes Read entire scratchpad plus CRC The master now recal culates the CRC of the eight data bytes received from the scratchpad com...

Страница 23: ...FFh all bits 1 TX Reset Reset pulse RX Presence Presence pulse TX CCh Skip ROM command TX BEh Read Scratchpad command RX 9 data bytes Read entire scratchpad plus CRC The master now recal culates the C...

Страница 24: ...ility RECOMMENDED DC OPERATING CONDITIONS PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTES Supply Voltage VDD I O Functions 1 2 C Accurate Temperature Conversions 2 8 4 3 5 0 5 5 5 5 V 1 2 Data Pin...

Страница 25: ...3 4 volts 2 All voltages are referenced to ground 3 Logic one voltages are specified at a source current of 1 mA 4 Logic zero voltages are specified at a sink current of 4 mA 5 IDD specified with VCC...

Страница 26: ...WRITE ZERO TIME SLOT START OF NEXT CYCLE tREC tSLOT tLOW0 1 WIRE READ ZERO TIME SLOT START OF NEXT CYCLE tREC tSLOT tRDV 1 WIRE RESET PULSE RESET PULSE FROM HOST PRESENCE DETECT 1 WIRE PRESENCE DETECT...

Страница 27: ...PERFORMANCE CURVE 55 35 15 5 25 45 65 85 105 125 5 4 3 2 1 1 2 3 UPPER LIMIT SPECIFICATION TYPICAL LOWER LIMIT SPECIFICATION DS1820 DIGITAL TERMOMETER AND THERMOSTAT TEMPERATURE READING ERROR ERROR de...

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