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中英文资料中英文资料
The introduction to The DS18B20 1. DESCRIPTION
The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements and has an alarm function with nonvolatile ur programmable upper
and lower trigger points. The DS18B20 communicates over a 1-Wire bus that by
definition requires only one data line for communication with a central
microprocessor. It has an operating temperature range of -55°-55°C C to +125°+125°C C and is accurate to ±0.5°0.5°C over the range of C over the range of -10°-10°C to +85°C to +85°C to +85°C. In addition, the DS18B20 C. In addition, the DS18B20
can derive power directly from the data line (―parasite powerǁ), eliminating the need
for an external power supply.
kabEach DS18B20 has a unique 64-bit rial code, which allows multiple DS18B20s to function on the same 1-Wire bus. Thus, it is simple to u one
microprocessor to control many DS18B20s distributed over a large area. Applications
that can benefit from this feature include HV that can benefit from this feature include HVAC environmental controls, temperature AC environmental controls, temperature
monitoring systems inside buildings, equipment, or machinery, and process
monitoring and control systems.
2.FEA TURES
l Unique 1-Wire® Interface Requires Only One Port Pin for Communication
l Each Device has a Unique 64-Bit Serial Code Stored in an On-Board ROM
l Multi-drop Capability Simplifies Distributed Temperature-Sensing Applications
l Requires No External Components
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2 l Can Be Powered from Data Line; Power Supply Range is 3.0V to 5.5V
l Measures Temperatures from -55°C to +125°C to +125°C (-67°
C (-67°C (-67°F to +257°F to +257°F to +257°F) F) l ±0.5°0.5°C Accuracy from -10°
C Accuracy from -10°C Accuracy from -10°C to +85°C to +85°C to +85°C C l Thermometer Resolution is Ur Selectable from 9 to 12 Bits
l Converts Temperature to 12-Bit Digital Word in 750ms (Max)
l Ur-Definable Nonvolatile (NV) Alarm Settings
12星座谁是学霸
l Alarm Search Command Identifies and Address Devices Who Temperature is
Outside Programmed Limits
l Software Compatible with the DS1822
l Applications Include Thermostatic Controls, Industrial Systems, Consumer
Products, Thermometers, or Any Thermally Sensitive System
3.OVERVIEW
Figure 1 shows a block diagram of the DS18B20, and pin descriptions are given
in the Pin Description table. The 64-in the Pin Description table. The 64-bit ROM stores the device’s unique rial code. bit ROM stores the device’s unique rial code.
The scratchpad memory contains the 2-byte temperature register that stores the digital
output from the temperature nsor. In addition, the scratchpad provides access to the
1-byte upper and lower alarm trigger registers (TH and TL) and the 1-byte
configuration register. The configuration register allows the ur to t the resolution
of the temperature to-digital conversion to 9, 10, 11, or 12 bits. The TH, TL, and
configuration registers are nonvolatile (EEPROM), so they will retain data when the
device is powered down.
The DS18B20 us Maxim’s exclusive 1-Wire bus protocol that implements bus
communication using one control signal. The control line requires a weak pull up
resistor since all devices are linked to the bus via a 3-state or open-drain port (the DQ
pin in the ca of the DS18B20). In this bus system, the microprocessor (the master
device) identifies and address devices on the bus using each device’s unique 64-bit
code. Becau each device has a unique code, the number of devices that can be
addresd on one DS18B20 bus is virtually unlimited. The 1-Wire bus protocol,
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3 including detailed explanations of the commands and “time slots,ǁ is covered in the朱自清经典常谈
1-Wire Bus System ction.
Another feature of the DS18B20 is the ability to operate without an external power supply. Power is instead supplied through the 1-Wire pull up resistor via the
DQ pin when the bus is high. The high bus signal also charges an internal capacitor
(CPP), which then supplies power to the device when the bus is low. This method of
deriving power from the 1-1-Wire Wire bus is referred to as ―parasite p ower.ǁ power.ǁ As an alternative, the DS18B20 may also be powered by an external supply on VDD.
64-BIT ROM AND 1-WIRE PORT
老干妈拌饭MEMORY CONTROL LOGIC
SCRATCHPAD TEMPERATURE SENSOR ALARM HIGH TRIGGER (TH) ALARM LOW TRIGGER (TL)
CONFIGURATION REGISTER 8-BIT CRC GENERATOR
POWER-
SUPPLY
SENSE INTERNAL Vdd PARASITE POWER CIRCUIT Cpp Vpu
4.7K DQ
GND
Vdd高血糖吃什么好
Figure 1.DS18B20 Block Diagram 4.OPERA TION —MEASURING TEMPERATUR
The core functionality of the DS18B20 is its direct-to-digital temperature nsor.
The resolution of the temperature nsor is ur-configurable to 9, 10, 11, or 12 bits,
corresponding to increments of 0.5°corresponding to increments of 0.5°C, 0.25°C, 0.25°C, 0.25°C, 0.125°C, 0.125°C, 0.125°C, and 0.0625°C, and 0.0625°C, and 0.0625°C, respectively. C, respectively.
The default resolution at power-up is 12-bit. The DS18B20 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. Following the conversion, the resulting
thermal data is stored in the 2-byte temperature register in the scratchpad memory and
the DS18B20 returns to its idle state. If the DS18B20 is powered by an external
supply, the master can issue ―read time slotsǁ (e the 1-Wire Bus System ction)
after the Convert T command and the DS18B20 will respond by transmitting 0 while
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4 the temperature conversion is in progress and 1 when the conversion is done. If the
DS18B20 is powered with parasite power, this notification technique cannot be ud
since the bus must be pulled high by a strong pull up during the entire temperature conversion.
The DS18B20 output temperature data is calibrated in degrees Celsius; for
Fahrenheit applications, a lookup table or conversion routine must be ud. The
temperature data is stored as a 16-bit sign-temperature data is stored as a 16-bit sign-extended two’s complement number in the extended two’s complement number in the temperature register (e Figure 2). The sign bits (S) indicate if the temperature is
positive or negative: for positive numbers S = 0 and for negative numbers S = 1. If
the DS18B20 is configured for 12-bit resolution, all bits in the temperature register
will contain valid data. For 11-bit resolution, bit 0 is undefined. For 10-bit resolution, bits 1 and 0 are undefined, and for 9-bit resolution bits 2, 1, and 0 are undefined.
Table 1 gives examples of digital output data and the corresponding temperature
reading for 12-bit resolution conversions.
bit7 bit6 bit5 bit4 bit3 bit2 bit1
bit0 LS Byte 23
22 21 20 2-1 2-2 2-3 2-4 bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 MS Byte
S S S S S 26 25 24 Figure 2.Temperature Register Format
TEMPERATURE DIGITAL OUTPUT (BINARY) DIGITAL OUTPUT
(HEX)
+125℃ 0000 0111 1101 0000 07D0H
+25.0625+25.0625℃℃
栀子花简笔画0000 0001 1001 0001 0191H 0℃
0000 0000 0000 0000 0000H -25.0625-25.0625℃℃
1111 1110 0110 1111 FE6FH -55-55℃℃ 1111 1100 1001 0000 FC90H
Table 1.Temperature/Data Relationship
5.64-BIT LASERED ROM CODE
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5 Each DS18B20 contains a unique 6464––bit code (e Figure 3) stored in ROM.
The least significant 8 bits of the ROM code contain the DS18B20’s 1-Wire family
code: 28h. The next 48 bits contain a unique rial number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from the first
56 bits of the ROM code. The 64-bit ROM code and associated ROM function
control logic allow the DS18B20 to operate as a 1-Wire device using the protocol
detailed in the 1-Wire Bus System ction.
8-BIT CRC 48-BIT SERIAL NUMBER 8-BIT FAMILY CODE
MSB LSB MSB LSB MSB
怎么画小猪Figure 3.64-Bit Lared ROM Code
6.MEMORY
The DS18B20’s memory is organized as shown in Figure 4. The memory
consists of an SRAM scratchpad with nonvolatile EEPROM storage for the high and
low alarm trigger registers (TH and TL) and configuration register. Note that if the
DS18B20 alarm function is not ud, the TH and TL registers can rve as
general-purpo memory.
Byte 0 and byte 1 of the scratchpad contain the LSB and the MSB of the
temperature register, respectively. The bytes are read-only. Bytes 2 and 3 provide access to TH and TL registers. Byte 4 contains the configuration register data. Bytes 5,
6, and 7 are rerved for internal u by the device and cannot be overwritten. Byte 8
of the scratchpad is read-only and contains the CRC code for bytes 0 through 7 of the
scratchpad. The DS18B20 generates this CRC using the method described in the CRC Generation ction.
Data is written to bytes 2, 3, and 4 of the scratchpad using the Write Scratchpad
[4Eh] command; the data must be transmitted to the DS18B20 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. When reading the
scratchpad, data is transferred over the 1-Wire bus starting with the least significant
