DS1825U/T&R [MAXIM]
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MAXIM INTEGRATED PRODUCTS |
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DS1825
Programmable Resolution 1-Wire
Digital Thermometer With 4-Bit ID
FEATURES
PIN ASSIGNMENT
ꢀ
Cꢀ Unique 1-Wire Interface Requires Only One
Port Pin for Communication
1
8
7
Cꢀ Each Device has a Unique 64-Bit Serial Code
Stored in an On-Board ROM
VDD
AD3
AD2
AD1
AD0
Cꢀ Multidrop Capability Simplifies Distributed
Temperature-Sensing Applications
Cꢀ 4 Pin-Programmable Bits to Uniquely Identify
Up to 16 Sensor Locations on a Bus
Cꢀ Requires No External Components
Cꢀ Can be Powered from Data Line. Power Supply
Range: 3.0V to 3.7V
2
DQ
DS1825
6
3
4
8-pin ꢀSOP
5
N.C.
Cꢀ Measures Temperatures from -55°C to +125°C
(-67°F to +257°F)
GND
Cꢀ M0.5LC Accuracy from -10°C to +85°C
Cꢀ Thermometer Resolution is User-Selectable
from 9 to 12 Bits
µSOP
(DS1825U)
Cꢀ Converts Temperature to 12-Bit Digital Word in
750ms (max)
Cꢀ User-Definable (NV) Alarm Settings
Cꢀ Alarm Search Command Identifies and
Addresses Devices Whose Temperature is
Outside of Programmed Limits (Temperature
Alarm Condition)
PIN DESCRIPTION
GND
- Ground
DQ
- Data In/Out
- No Connect
N.C.
VDD
- Power Supply Voltage
- Address Pins
Cꢀ Available in 8-Pin ꢀSOP Package
Cꢀ Software Compatible with the DS1822
AD0 to AD3
APPLICATIONS
Thermostatic Controls
Industrial Systems
Consumer Products
Thermometers
1-Wire is a registered trademark of Dallas Semiconductor.
Thermally-Sensitive Systems
DESCRIPTION
The DS1825 digital thermometer provides 9 to 12-bit centigrade temperature measurements and has an alarm
function with NV user-programmable upper and lower trigger points. The DS1825 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 M0.5LC over the range of -10°C to +85°C. In
addition, the DS1825 can derive power directly from the data line (“parasite power”), eliminating the need for an
external power supply.
ORDERING INFORMATION
ORDERING NUMBER
PACKAGE MARKING
DESCRIPTION
DS1825U
1825
8-pin µSOP
DS1825U/T&R
DS1825U+
1825
8-pin µSOP Tape-and-Reel
8-pin ꢀSOP, Lead Free
1825 (See Note 1)
1825 (See Note 1)
DS1825U+T&R
8-pin µSOP Tape-and-Reel, Lead Free
Note 1: Additionally, a "+" symbol will be marked on the package.
1 of 21
Rev 020105
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
DESCRIPTION (cont.)
Each DS1825 has a unique 64-bit serial code, which allows multiple DS1825s to function on the same 1-Wire bus;
thus, it is simple to use one microprocessor to control many DS1825s distributed over a large area. In addition, the
4-bit location address can be used to identify specific temperature sensors in the system without requiring a wide
lookup table. 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.
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature Range
Storage Temperature Range
Solder Dip Temperature (10s)
Reflow Oven Temperature
-0.5V to +6.0V
L
-55 C to +125LC
L
L
-55 C to +125 C
L
+260 C
L
+220 C
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.
DC ELECTRICAL CHARACTERISTICS
(-55°C to +125°C; VDD= 3.0V to 3.7V)
PARAMETER
SYMBOL
CONDITION
Local Power
MIN
+3.0
+3.0
+3.0
TYP
MAX
+3.7
+3.7
VDD
UNITS
NOTES
Supply Voltage
VDD
V
1
Parasite Power
Local Power
Pullup Supply Voltage
VPU
V
1, 2
-10°C to +85°C
-55°C to +125°C
±0.5
±2
°C
°C
Thermometer Error
tERR
3
Programming
RPGM
0
10
12
kꢁ
Resistor: AD0-AD3
DQ Input Logic Low
VIL(DQ)
-0.3
+0.7
V
1, 4, 5
The lower of
3.7
Local Power
+2.2
DQ Input Logic High
VIH(DQ)
V
1, 6
or
Parasite Power
VI/O = 0.4V
+3.0
4.0
VDD + 0.3
Sink Current
Standby Current
Active Current
DQ Input Current
Drift
IL
mA
nA
mA
µA
°C
1
7, 8
9
IDDS
IDD
IDQ
500
0.65
5
1000
1.5
VDD = 3.7V
10
11
±0.2
NOTES:
1.
2.
All voltages are referenced to ground.
The Pullup Supply Voltage specification assumes that the pullup device is ideal, and therefore the high level of the pullup is equal to VPU
.
In order to meet the VIH spec of the DS1825, 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: VPU_ACTUAL = VPU_IDEAL + VTRANSISTOR
.
3.
4.
5.
6.
7.
8.
9.
See typical performance curve in Figure 18
Logic low voltages are specified at a sink current of 4mA.
To guarantee a presence pulse under low voltage parasite power conditions, VILMAX may have to be reduced to as low as 0.5V.
Logic high voltages are specified at a source current of 1mA.
Standby current specified up to 70LC. Standby current typically is 3ꢀA at 125LC.
To minimize IDDS, DQ should be within the following ranges: GND ? DQ ? GND + 0.3V or VDD - 0.3V ? DQ ? VDD
.
Active current refers to supply current during active temperature conversions or EEPROM writes.
10. DQ line is high (“hi-Z” state).
11. Drift data is based on a 1000 hour stress test at 125°C.
12. Inputs AD0-AD3 must be tied either High or Low. A "Low" is a connection to the GND terminal. A "High" connection varies with usage of
the DS1825. When connected as a parasite powered sensor, a connection to DQ is considered a High. When powered through the VDD
pin, a connection to VDD is a High. If left floating, the input values are indeterminate and may be either logical "0" or logical "1." See
Figures 20 and 21 for details. When optional programming resistors are used, their maximum values are 10,000ꢁ.
2 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
AC ELECTRICAL CHARACTERISTICS: NV MEMORY
(-55°C to +100°C; VDD = 3.0V to 3.7V)
PARAMETER
NV Write Cycle Time
EEPROM Writes
SYMBOL
twr
CONDITION
MIN
TYP
MAX
UNITS
ms
2
10
NEEWR
tEEDR
-55°C to +55°C
-55°C to +55°C
50k
10
writes
years
EEPROM Data Retention
AC ELECTRICAL CHARACTERISTICS
(-55°C to +125°C; VDD = 3.0V to 3.7V)
PARAMETER
SYMBOL
CONDITION
9-bit resolution
10-bit resolution
11-bit resolution
12-bit resolution
Start Convert T
Command Issued
MIN
TYP
MAX
93.75
187.5
375
UNITS
ms
NOTES
1
1
1
1
Temperature Conversion
Time
ms
tCONV
ms
750
ms
10
µs
Time to Strong Pullup On
tSPON
Time Slot
tSLOT
60
1
120
µs
µs
µs
µs
µs
µs
µs
µs
µs
pF
pF
1
1
Recovery Time
tREC
Write 0 Low Time
Write 1 Low Time
Read Data Valid
Reset Time High
Reset Time Low
Presence Detect High
Presence Detect Low
Capacitance: DQ
Capacitance: AD0-AD3
tLOW0
tLOW1
tRDV
60
1
120
15
1
1
15
1
tRSTH
480
480
15
1
tRSTL
1, 2
1
tPDHIGH
tPDLOW
CIN/OUT
CIN_AD
60
240
25
60
1
50
NOTES:
1.
2.
Refer to timing diagrams in Figure 18.
Under parasite power, if tRSTL > 960ꢀs, a power on reset may occur.
Table 1. DETAILED PIN DESCRIPTIONS
PIN
4
SYMBOL
DESCRIPTION
GND
Ground.
2
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.)
DQ
1
Optional VDD pin. VDD must be grounded for operation in parasite
VDD
power mode.
5
6
7
8
3
AD0
AD1
AD2
AD3
N.C.
Location Address Input Pin LSB
Location Address Input Pin
Location Address Input Pin
Location Address Input Pin MSB
No Connection
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DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
OVERVIEW
Figure 1 shows a block diagram of the DS1825, and pin descriptions are given in Table 1. The 64-bit ROM stores
the device’s unique serial code. The scratchpad memory contains the 2-byte temperature register that stores the
digital output from the temperature sensor. 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
user to set the resolution of the temperature-to-digital conversion to 9, 10, 11, or 12 bits. It is also used for the hard-
wired address programmed by the AD0-AD3 pins. The TH, TL, and configuration registers are NV (EEPROM), so
they will retain data when the device is powered down.
The DS1825 uses Dallas’ exclusive 1-Wire bus protocol that implements bus communication using one control
signal. The control line requires a weak pullup resistor since all devices are linked to the bus through a 3-state or
open-drain port (the DQ pin in the case of the DS1825). In this bus system, the microprocessor (the master device)
identifies and addresses devices on the bus using each device’s unique 64-bit code. Because each device has a
unique code, the number of devices that can be addressed on one bus is virtually unlimited. The 1-Wire bus
protocol, including detailed explanations of the commands and “time slots,” is covered in the 1-Wire BUS SYSTEM
section of this data sheet.
Another feature of the DS1825 is the ability to operate without an external power supply. Power is instead supplied
through the 1-Wire pullup resistor through 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-Wire bus is referred to as “parasite power.” As an alternative, the DS1825 can also be powered
by an external supply on VDD.
Figure 1. DS1825 BLOCK DIAGRAM
VPULLUP
4.7k
Memory
DQ
Control Logic
Parasite
Power
Circuit
16-bit Temp Reg
8-bit TH Register
8-bit TL Register
8-bit CRC Gen
S
C
R
A
T
64-Bit ROM
And
GND
Cpp
1-wire Port
C
P
A
D
Power
Supply
Sense
VDD
8-bit Config. Reg
Address Pin
Input Latch
AD0-AD3
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DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
OPERATIONZMEASURING TEMPERATURE
The core functionality of the DS1825 is its direct-to-digital temperature sensor. The resolution of the temperature
sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5LC, 0.25LC, 0.125LC, and
0.0625LC, respectively. The default resolution at power-up is 12-bit. The DS1825 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 12-bit temperature register in the
scratchpad memory and the DS1825 returns to its idle state. If the DS1825 is powered by an external supply, the
master can issue “read time slots” (see the 1-Wire BUS SYSTEM section) after the Convert T command and the
DS1825 will respond by transmitting 0 while the temperature conversion is in progress and 1 when the conversion
is done. If the DS1825 is powered with parasite power, this notification technique cannot be used since the bus
must be pulled high by a strong pullup during the entire temperature conversion. The bus requirements for parasite
power are explained in detail in the POWERING THE DS1825 section of this data sheet.
The DS1825 output temperature data is calibrated in degrees centigrade; for Fahrenheit applications, a lookup
table or conversion routine must be used. The temperature data is stored as a 16-bit sign-extended two’s
complement number in the temperature register (see 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 DS1825 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 3 gives
examples of digital output data and the corresponding temperature reading for 12-bit resolution conversions.
Figure 2. TEMPERATURE REGISTER FORMAT
bit 7
bit 6
bit 5
bit 4
bit 3
2-1
bit 2
2-2
bit 1
2-3
bit 0
2-4
LS Byte
23
22
21
20
bit 15
S
bit 14
S
bit 13
S
bit 12
S
bit 11
S
bit 10
26
bit 9
25
bit 8
24
MS Byte
Table 3. TEMPERATURE/DATA RELATIONSHIP
DIGITAL OUTPUT
TEMPERATURE
DIGITAL OUTPUT
(Hex)
(Binary)
+125°C
+85°C*
+25.0625°C
+10.125°C
+0.5°C
0°C
-0.5°C
-10.125°C
-25.0625°C
-55°C
0000 0111 1101 0000
0000 0101 0101 0000
0000 0001 1001 0001
0000 0000 1010 0010
0000 0000 0000 1000
0000 0000 0000 0000
1111 1111 1111 1000
1111 1111 0101 1110
1111 1110 0110 1111
1111 1100 1001 0000
07D0h
0550h
0191h
00A2h
0008h
0000h
FFF8h
FF5Eh
FE6Fh
FC90h
*The power-on reset value of the temperature register is +85°C
OPERATIONZALARM SIGNALING
After the DS1825 performs a temperature conversion, the temperature value is compared to the user-defined 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 NV (EEPROM) so they will retain data when the device is powered down. TH and TL can be accessed
through bytes 2 and 3 of the scratchpad as explained in the MEMORY section of this data sheet.
5 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
Figure 3. TH AND TL REGISTER FORMAT
bit 7
S
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
26
25
25
25
22
21
20
Only bits 11 through 4 of the temperature register are used in the TH and TL comparison since TH and TL are 8-bit
registers. If the measured temperature is lower than or equal to TL or higher than or equal to TH, an alarm condition
exists and an alarm flag is set inside the DS1825. This flag is updated after every temperature measurement;
therefore, if the alarm condition goes away, the flag will be turned off after the next temperature conversion.
The master device can check the alarm flag status of all DS1825s on the bus by issuing an Alarm Search [ECh]
command. Any DS1825s with a set alarm flag will respond to the command, so the master can determine exactly
which DS1825s have experienced an alarm condition. If an alarm condition exists and the TH or TL settings have
changed, another temperature conversion should be done to validate the alarm condition.
POWERING THE DS1825
The DS1825 can be powered by an external supply on the VDD pin, or it can operate in “parasite power” mode,
which allows the DS1825 to function without a local external supply. Parasite power is very useful for applications
that require remote temperature sensing or that are very space constrained. Figure 1 shows the DS1825’s
parasite-power control circuitry, which “steals” power from the 1-Wire bus through the DQ pin when the bus is high.
The stolen charge powers the DS1825 while the bus is high, and some of the charge is stored on the parasite
power capacitor (CPP) to provide power when the bus is low. When the DS1825 is used in parasite power mode,
the VDD pin must be connected to ground.
In parasite power mode, the 1-Wire bus and CPP can provide sufficient current to the DS1825 for most operations
as long as the specified timing and voltage requirements are met (refer to the DC ELECTRICAL
CHARACTERISTICS and the AC ELECTRICAL CHARACTERISTICS sections of this data sheet). However, when
the DS1825 is performing temperature conversions or copying data from the scratchpad memory to EEPROM, the
operating current can be as high as 1.5mA. This current can cause an unacceptable voltage drop across the weak
1-Wire pullup resistor and is more current than can be supplied by CPP. To assure that the DS1825 has sufficient
supply current, it is necessary to provide a strong pullup on the 1-Wire bus whenever temperature conversions are
taking place or data is being copied from the scratchpad to EEPROM. This can be accomplished by using a
MOSFET to pull the bus directly to the rail as shown in Figure 4. The 1-Wire bus must be switched to the strong
pullup within 10ꢀs (max) after a Convert T [44h] or Copy Scratchpad [48h] command is issued, and the bus must
be held high by the pullup for the duration of the conversion (tconv) or data transfer (twr = 10ms). No other activity can
take place on the 1-Wire bus while the pullup is enabled.
The DS1825 can also be powered by the conventional method of connecting an external power supply to the VDD
pin, as shown in Figure 5. The advantage of this method is that the MOSFET pullup is not required, and the 1-Wire
bus is free to carry other traffic during the temperature conversion time.
The use of parasite power is not recommended for temperatures above 100LC since the DS1825 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 DS1825 be powered by an
external power supply.
In some situations the bus master may not know whether the DS1825s on the bus are parasite powered or
powered by external supplies. The master needs this information to determine if the strong bus pullup should be
used during temperature conversions. To get this information, the master can issue a Skip ROM [CCh] command
followed by a Read Power Supply [B4h] command followed by a “read time slot”. During the read time slot, parasite
powered DS1825s will pull the bus low, and externally powered DS1825s will let the bus remain high. If the bus is
pulled low, the master knows that it must supply the strong pullup on the 1-Wire bus during temperature
conversions.
6 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
Figure 4. SUPPLYING THE PARASITE-POWERED DS1825 DURING
TEMPERATURE CONVERSIONS
VPU
DS1825
GND
DQ VDD
VPU
Micro-
processor
4.7K
To Other
1-Wire Bus
1-Wire Devices
Figure 5. POWERING THE DS1825 WITH AN EXTERNAL SUPPLY
VDD (External Supply)
DS1825
VPU
4.7K
Micro-
GND
DQ VDD
processor
To Other
1-Wire Devices
1-Wire Bus
64-BIT LASERED ROM CODE
Each DS1825 contains a unique 64-bit code (see Figure 6) stored in ROM. The least significant 8 bits of the ROM
code contain the DS1825’s 1-Wire family code: 3Bh. The next 48 bits contain a unique serial 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. A detailed explanation of the CRC bits is provided in the CRC GENERATION section. The 64-bit ROM code
and associated ROM function control logic allow the DS1825 to operate as a 1-Wire device using the protocol
detailed in the 1-Wire BUS SYSTEM section of this data sheet.
Figure 6. 64-BIT LASERED ROM CODE
8-BIT CRC
48-BIT SERIAL NUMBER
8-BIT FAMILY CODE (3Bh)
MSB LSB
MSB
LSB MSB
LSB
MEMORY
The DS1825’s memory is organized as shown in Figure 7. The memory consists of an SRAM scratchpad with NV
EEPROM storage for the high and low alarm trigger registers (TH and TL) and configuration register. Note that if the
DS1825 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 DS1825 FUNCTION COMMANDS section.
Byte 0 and byte 1 of the scratchpad contain the LSB and the MSB of the temperature register, respectively. These
bytes are read-only. Bytes 2 and 3 provide access to TH and TL registers. Byte 4 contains the configuration register
data, which is explained in detail in the CONFIGURATION REGISTER section of this data sheet. Bytes 5, 6, and 7
are reserved for internal use by the device and cannot be overwritten.
7 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
Byte 8 of the scratchpad is read-only and contains the cyclic redundancy check (CRC) code for bytes 0 through 7
of the scratchpad. The DS1825 generates this CRC using the method described in the CRC GENERATION
section.
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 DS1825 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 bit of byte 0. To transfer the TH, TL, and
configuration data from the scratchpad to EEPROM, the master must issue the Copy Scratchpad [48h] command.
Data in the EEPROM registers is retained when the device is powered down; at power-up the EEPROM data
(including the hard-wired address inputs AD0-AD3)is reloaded into the corresponding scratchpad locations. Data
can also be reloaded from EEPROM to the scratchpad at any time using the Recall E2 [B8h] command. The master
can issue read time slots following the Recall E2 command and the DS1825 will indicate the status of the recall by
transmitting 0 while the recall is in progress and 1 when the recall is done.
Figure 7. DS1825 MEMORY MAP
SCRATCHPAD (Power-up State)
byte 0 Temperature LSB (50h)
(85°C)
byte 1 Temperature MSB (05h)
byte 2 TH Register or User Byte 1
byte 3 TL Register or User Byte 2
byte 4 Configuration Register*
byte 5 Reserved
EEPROM
TH Register or User Byte 1
TL Register or User Byte 2
Configuration Register*
byte 6 Reserved
byte 7 Reserved
byte 8 CRC
* Lower four bits of Configuration Register
are hardwired through AD0-AD3
CONFIGURATION REGISTER
Byte 4 of the scratchpad memory is the configuration register, as shown in Figure 8. The configuration register
allows the user to set the conversion resolution using the R0 and R1 bits and read the programmed value of the
address pins. The conversion resolution power-up default is R0 = 1 and R1 = 1 (12-bit resolution). Table 4 shows
the resolution configuration settings and maximum conversion time. Note that there is a direct tradeoff between
resolution and conversion time. AD0-AD3 bits report the pin programmed location information and are sampled at
power-up. In Parasite Power mode, the address pins must be connected to DQ or GND and in VDD powered mode,
the address pins must be connected to VDD or GND. Pins tied to DQ/VDD are reported with a logical 1 and pins tied
to GND are reported as a logical 0. Pins connected to DQ/ VDD or GND through a resistor are valid logical 1s or
logical 0s if the resistor is less than 10k. Floating or high impedance (>10kꢁ) connections are indeterminate. Bit 7
and Bit 4 of the configuration register are reserved for internal use and cannot be overwritten.
Figure 8. CONFIGURATION REGISTER FORMAT
Note: Bit 0 through Bit 3 are programmed through the four Location Programming Address pins AD0-AD3.
Reading the configuration register provides location information on up to 16 individual DS1825s.
bit 7
0
bit 6
R1
bit 5
R0
bit 4
1
bit 3
AD3
bit 2
AD2
bit 1
AD1
bit 0
AD0
8 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
Table 4. THERMOMETER RESOLUTION CONFIGURATION
R1
0
0
R0
0
1
Resolution
9-bit
Max Conversion Time
93.75ms
187.5ms
375ms
(tCONV/8)
(tCONV/4)
(tCONV/2)
10-bit
11-bit
1
0
1
1
12-bit
750ms
(tCONV)
CRC GENERATION
CRC bytes are provided as part of the DS1825’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 DS1825. 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) or to the scratchpad CRC (for scratchpad reads). If the calculated CRC matches the read CRC, the data has
been received error free. The comparison of CRC values and the decision to continue with an operation are
determined entirely by the bus master. There is no circuitry inside the DS1825 that prevents a command sequence
from proceeding if the DS1825 CRC (ROM or scratchpad) does not match the value generated by the bus master.
The equivalent polynomial function of the CRC (ROM or scratchpad) is:
CRC = X8 + X5 + X4 + 1
The bus master can re-calculate the CRC and compare it to the CRC values from the DS1825 using the polynomial
generator shown in Figure 9. This circuit consists of a shift register and XOR gates, and the shift register bits are
initialized to 0. Starting with the least significant bit of the ROM code or the least significant bit of byte 0 in the
scratchpad, one bit at a time should shifted into the shift register. After shifting in the 56th bit from the ROM or the
most significant bit of byte 7 from the scratchpad, the polynomial generator will contain the re-calculated CRC.
Next, the 8-bit ROM code or scratchpad CRC from the DS1825 must be shifted into the circuit. At this point, if the
re-calculated CRC was correct, the shift register will contain all 0s. Additional information about the Dallas 1-Wire
cyclic redundancy check is available in Application Note 27 entitled “Understanding and Using Cyclic Redundancy
Checks with Dallas Semiconductor Touch Memory Products.”
Figure 9. CRC GENERATOR
INPUT
XOR
XOR
XOR
(MSB)
(LSB)
1-Wire BUS SYSTEM
The 1-Wire bus system uses a single bus master to control one or more slave devices. The DS1825 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
“multidrop” if there are multiple slaves on the bus.
All data and commands are transmitted least significant bit first over the 1-Wire bus.
The following discussion of the 1-Wire bus system is broken down into three topics: hardware configuration,
transaction sequence, and 1-Wire signaling (signal types and timing).
9 of 21
HARDWARE CONFIGURADTSIO18N25 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
The 1-Wire bus has by definition only a single data line. Each device (master or slave) interfaces to the data line
through an open-drain or 3-state port. This allows each device to “release” the data line when the device is not
transmitting data so the bus is available for use by another device. The 1-Wire port of the DS1825 (the DQ pin) is
open drain with an internal circuit equivalent to that shown in Figure 10.
The 1-Wire bus requires an external pullup resistor of approximately 5kꢁ; thus, the idle state for the 1-Wire bus is
high. If for any reason 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 as the 1-Wire bus is in the inactive (high) state
during the recovery period. If the bus is held low for more than 480ꢀs, all components on the bus will be reset.
Figure 10. HARDWARE CONFIGURATION
VPU
DS1825 1-WIRE PORT
DQ
4.7K
1-Wire Bus
T
5
T
µA
100ꢀ
MOSFET
RX =
RECEIVE
TX =
TRANSMIT
TRANSACTION SEQUENCE
The transaction sequence for accessing the DS1825 is as follows:
Step 1. Initialization
Step 2. ROM Command (followed by any required data exchange)
Step 3. DS1825 Function Command (followed by any required data exchange)
It is very important to follow this sequence every time the DS1825 is accessed, as the DS1825 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.
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 DS1825) are on the bus and are ready to operate.
Timing for the reset and presence pulses is detailed in the 1-Wire SIGNALING section.
ROM COMMANDS
After the bus master has detected a presence pulse, it can issue a ROM command. These commands operate on
the unique 64-bit ROM codes of each slave device and allow the master to single out a specific device if many are
present on the 1-Wire bus. These commands also allow the master to determine how many and what types of
devices are present on the bus or if any device has experienced an alarm condition. There are five ROM
commands, and each command is 8 bits long. The master device must issue an appropriate ROM command
before issuing a DS1825 function command. A flowchart for operation of the ROM commands is shown in Figure
11.
10 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
SEARCH ROM [F0h]
When a system is initially powered up, the master must identify the ROM codes of all slave devices on the bus,
which allows the master to determine the number of slaves and their device types. The master learns the ROM
codes through a process of elimination that requires the master to perform a Search ROM cycle (i.e., Search ROM
command followed by data exchange) as many times as necessary to identify all of the slave devices. If there is
only one slave on the bus, the simpler Read ROM command (see below) can be used in place of the Search ROM
process. For a detailed explanation of the Search ROM procedure, refer to the iButtonꢂ Book of Standards at
www.ibutton.com/ibuttons/standard.pdf. After every Search ROM cycle, the bus master must return to Step 1
(Initialization) in the transaction sequence.
READ ROM [33h]
This command can only be used when there is one slave on the bus. It allows the bus master to read the slave’s
64-bit ROM code without using the Search ROM procedure. If this command is used when there is more than one
slave present on the bus, a data collision will occur when all the slaves attempt to respond at the same time.
MATCH ROM [55h]
The match ROM command followed by a 64-bit ROM code sequence allows the bus master to address a specific
slave device on a multidrop or single-drop bus. Only the slave that exactly matches the 64-bit ROM code sequence
will respond to the function command issued by the master; all other slaves on the bus will wait for a reset pulse.
SKIP ROM [CCh]
The master can use this command to address all devices on the bus simultaneously without sending out any ROM
code information. For example, the master can make all DS1825s on the bus perform simultaneous temperature
conversions by issuing a Skip ROM command followed by a Convert T [44h] command.
Note that the Read Scratchpad [BEh] command can follow the Skip ROM command only if there is a single slave
device on the bus. In this case time is saved by allowing the master to read from the slave without sending the
device’s 64-bit ROM code. A Skip ROM command followed by a Read Scratchpad command will cause a data
collision on the bus if there is more than one slave since multiple devices will attempt to transmit data
simultaneously.
ALARM SEARCH [ECh]
The operation of this command is identical to the operation of the Search ROM command except that only slaves
with a set alarm flag will respond. This command allows the master device to determine if any DS1825s
experienced an alarm condition during the most recent temperature conversion. After 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 OPERATIONZALARM SIGNALING section for an explanation of alarm flag
operation.
DS1825 FUNCTION COMMANDS
After the bus master has used a ROM command to address the DS1825 with which it wishes to communicate, the
master can issue one of the DS1825 function commands. These commands allow the master to write to and read
from the DS1825’s scratchpad memory, initiate temperature conversions and determine the power supply mode.
The DS1825 function commands, which are described below, are summarized in Table 5 and illustrated by the
flowchart in Figure 12.
CONVERT T [44h]
This command initiates a single temperature conversion. Following the conversion, the resulting thermal data is
stored in the 2-byte temperature register in the scratchpad memory and the DS1825 returns to its low-power idle
state. If the device is being used in parasite power mode, within 10ꢀs (max) after this command is issued the
master must enable a strong pullup on the 1-Wire bus for the duration of the conversion (tconv) as described in the
POWERING THE DS1825 section. If the DS1825 is powered by an external supply, the master can issue read time
slots after the Convert T command and the DS1825 will respond by transmitting 0 while the temperature
conversion is in progress and 1 when the conversion is done. In parasite power mode this notification technique
cannot be used since the bus is pulled high by the strong pullup during the conversion.
WRITE SCRATCHPAD [4Eh]
This command allows the master to write 3 bytes of data to the DS1825’s scratchpad. The first data byte is written
into the TH register (byte 2 of the scratchpad), the second byte is written into the TL register (byte 3), and the third
byte is written into the configuration register (byte 4). Data must be transmitted least significant bit first. All three
bytes MUST be written before the master issues a reset, or the data may be corrupted.
iButton is a registered trademark of Dallas Semiconductor.
11 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
READ SCRATCHPAD [BEh]
This command allows the master to read the contents of the scratchpad. The data transfer starts with the least
significant bit of byte 0 and continues through the scratchpad until the 9th byte (byte 8: CRC) is read. The master
may issue a reset to terminate reading at any time if only part of the scratchpad data is needed.
COPY SCRATCHPAD [48h]
This command copies the contents of the scratchpad TH, TL and configuration registers (bytes 2, 3, and 4) to
EEPROM. If the device is being used in parasite power mode, within 10ꢀs (max) after this command is issued the
master must enable a strong pullup on the 1-Wire bus for at least 10ms as described in the POWERING THE
DS1825 section.
RECALL E2 [B8h]
This command recalls the alarm trigger values (TH and TL) and configuration data from EEPROM and places the
data in bytes 2, 3, and 4, respectively, in the scratchpad memory. The master device can issue read time slots
following the Recall E2 command and the DS1825 will indicate the status of the recall by transmitting 0 while the
recall is in progress and 1 when the recall is done. The recall operation happens automatically at power-up, so
valid data is available in the scratchpad as soon as power is applied to the device.
READ POWER SUPPLY [B4h]
The master device issues this command followed by a read time slot to determine if any DS1825s on the bus are
using parasite power. During the read time slot, parasite powered DS1825s will pull the bus low, and externally
powered DS1825s will let the bus remain high. Refer to the POWERING THE DS1825 section for usage
information for this command.
Table 5. DS1825 FUNCTION COMMAND SET
1-Wire Bus Activity
Command
Description
Protocol
Notes
After Command is Issued
TEMPERATURE CONVERSION COMMANDS
DS1825 transmits conversion status
Initiates temperature
conversion.
Convert T
44h
to master (not applicable for
parasite-powered DS1825s).
1
MEMORY COMMANDS
Reads the entire scratchpad
including the CRC byte.
Writes data into scratchpad
bytes 2, 3, and 4 (TH, TL, and
configuration registers).
Copies TH, TL, and
DS1825 transmits up to 9 data
bytes to master.
Read Scratchpad
Write Scratchpad
BEh
2
3
Master transmits 3 data bytes to
DS1825.
4Eh
configuration register data
from the scratchpad to
EEPROM.
Copy Scratchpad
Recall E2
48h
None
1
Recalls TH, TL, and
configuration register data
from EEPROM to the
scratchpad.
DS1825 transmits recall status to
master.
B8h
B4h
Read Power
Supply
Signals DS1825 power supply
DS1825 transmits supply status to
master.
mode to the master.
NOTES:
1. For parasite-powered DS1825s, the master must enable a strong pullup on the 1-Wire bus during temperature
conversions and copies from the scratchpad to EEPROM. No other bus activity may take place during this
time.
2. The master can interrupt the transmission of data at any time by issuing a reset.
3. All three bytes must be written before a reset is issued.
12 of 21
Figure 11. ROM COMMANDDSS18F25LPOroWgramCmHaAbleRRTesolution 1-Wire Digital Thermometer With 4-Bit ID
Initialization
Sequence
MASTER TX
RESET PULSE
DS1825 TX
PRESENCE
PULSE
MASTER TX ROM
COMMAND
CCh
33h
55h
F0h
ECh
N
N
N
N
N
SKIP ROM
COMMAND
READ ROM
COMMAND
MATCH ROM
COMMAND
SEARCH ROM
COMMAND
ALARM SEARCH
COMMAND
Y
Y
Y
Y
Y
MASTER TX
BIT 0
DS1825 TX BIT 0
DS1825 TX BIT 0
MASTER TX BIT 0
DS1825 TX BIT 0
DS1825 TX BIT 0
MASTER TX BIT 0
DS1825 TX
FAMILY CODE
1 BYTE
N
N
DEVICE(S)
WITH ALARM
FLAG SET?
N
BIT 0
BIT 0
MATCH?
MATCH?
DS1825 TX
SERIAL NUMBER
6 BYTES
Y
Y
Y
DS1825 TX BIT 1
DS1825 TX BIT 1
MASTER TX BIT 1
MASTER TX
BIT 1
DS1825 TX
CRC BYTE
N
N
BIT 1
BIT 1
MATCH?
MATCH?
Y
Y
DS1825 TX BIT 63
DS1825 TX BIT 63
MASTER TX BIT 63
MASTER TX
BIT 63
N
N
BIT 63
BIT 63
MATCH?
MATCH?
Y
Y
MASTER TX
FUNCTION
COMMAND
(FIGURE 12)
13 of 21
Figure 12. DS1825 FUNCTDIOS1N82C5 POroMgrMamAmNabDleSReFsoLluOtioWn 1-CWHireADRigTital Thermometer With 4-Bit ID
44h
CONVERT
TEMPERATURE
?
48h
COPY
MASTER TX
FUNCTION
COMMAND
N
N
SCRATCHPAD
?
Y
Y
Y
Y
N
N
PARASITE
POWER
?
PARASITE
POWER
?
MASTER ENABLES
DS1825 BEGINS
STRONG PULL-UP ON DQ
MASTER ENABLES
CONVERSION
STRONG PULLUP ON DQ
DATA COPIED FROM
SCRATCHPAD TO EEPROM
DS1825 CONVERTS
TEMPERATURE
N
COPY IN
PROGRESS
?
DEVICE
CONVERTING
TEMPERATURE
?
N
MASTER DISABLES
STRONG PULLUP
Y
MASTER DISABLES
STRONG PULLUP
Y
MASTER
RX “0s”
MASTER
MASTER
MASTER
R
X “1s”
R
X “0s”
RX “1s”
B4h
READ
BEh
4Eh
N
B8h
RECALL E2
?
N
N
N
N
READ
WRITE
POWER SUPPLY
?
SCRATCHPAD
?
SCRATCHPAD
?
Y
Y
Y
Y
MASTER TX TH BYTE
TO SCRATCHPAD
MASTER RX DATA BYTE
FROM SCRATCHPAD
Y
PARASITE
POWERED
?
MASTER BEGINS DATA
RECALL FROM E2 PROM
MASTER TX TL BYTE
TO SCRATCHPAD
Y
MASTER
X “1s”
MASTER
RX “0s”
MASTER
TX RESET
?
R
MASTER TX CONFIG. BYTE
TO SCRATCHPAD
DEVICE
N
N
BUSY RECALLING
DATA
?
N
Y
HAVE 8 BYTES
BEEN READ
?
MASTER
RX “0s”
MASTER
RX “1s”
Y
MASTER RX SCRATCHPAD
CRC BYTE
RETURN TO INITIALIZATION
SEQUENCE (FIGURE 11) FOR
NEXT TRANSACTION
14 of 21
SUGGESTED PROCEDURDES1F8O25RPrBogUraImLmDaIbNleGReCsoRlutOionS1S-W-RireEDFigEitaRl TEhNermCoEmeTteAr BWiLthE4-Bit ID
This procedure uses the Search ROM command to find all DS1825s on the one-wire bus (16 maximum) and then
reads each configuration register to match the ROMIDs to the hard-wired addresses.
Figure 13
Search all
ROMIDs on bus &
BUILDING
store ROMIDs
CROSSREFERENCE
(F0h command)
TABLE USING
ROMIDS AND 4-BIT
ADDRESSES
Y
Increment Counter
N>Nmax?
N
DONE
N = N + 1
Nmax is the number
of ROMIDs found
Master Tx
Next ROMID
Crossreference Table
ROMID
AD3-AD0
ROMID(0)
ROMID(1)
ROMID(2)
ROMID(3)
0000
0001
0010
0011
Recall EEPROM
(use AD3-AD0
from Config
Register)
Match ROMID to
Address and Add
to Crossreference
Table
ROMID(12)
ROMID(13)
ROMID(14)
ROMID(15)
1100
1101
1110
1111
Note: Temperature sensors are addressed by
ROMID, not by binary address
15 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
1-Wire SIGNALING
The DS1825 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.
INITIALIZATION PROCEDURE: RESET AND PRESENCE PULSES
All communication with the DS1825 begins with an initialization sequence that consists of a reset pulse from the
master followed by a presence pulse from the DS1825. This is illustrated in Figure 13. When the DS1825 sends the
presence pulse in response to the reset, it is indicating to the master that it is on the bus and ready to operate.
During the initialization sequence the bus master transmits (TX) the reset pulse by pulling the 1-Wire bus low for a
minimum of 480ꢀs. The bus master then releases the bus and goes into receive mode (RX). When the bus is
released, the 5k pullup resistor pulls the 1-Wire bus high. When the DS1825 detects this rising edge, it waits 15–
60ꢀs and then transmits a presence pulse by pulling the 1-Wire bus low for 60–240ꢀs.
Figure 14. INITIALIZATION TIMING
MASTER TX RESET PULSE
MASTER RX
480 ꢀs minimum
480 ꢀs minimum
DS1825 TX
presence pulse
DS1825
60-240 ꢀs
waits 15-60 ꢀs
VPU
1-WIRE BUS
GND
LINE TYPE LEGEND
Bus master pulling low
DS1825 pulling low
Resistor pullup
READ/WRITE TIME SLOTS
The bus master writes data to the DS1825 during write time slots and reads data from the DS1825 during read time
slots. One bit of data is transmitted over the 1-Wire bus per time slot.
WRITE TIME SLOTS
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 DS1825 and a Write 0 time slot to write a logic 0 to the DS1825. All write time slots
must be a minimum of 60ꢀs in duration with a minimum of a 1ꢀs recovery time between individual write slots. Both
types of write time slots are initiated by the master pulling the 1-Wire bus low (see Figure 14).
To generate a Write 1 time slot, after pulling the 1-Wire bus low, the bus master must release the 1-Wire bus within
15ꢀs. When the bus is released, the 5k pullup resistor will pull the bus high. To generate a Write 0 time slot, after
pulling the 1-Wire bus low, the bus master must continue to hold the bus low for the duration of the time slot (at
least 60ꢀs).
The DS1825 samples the 1-Wire bus during a window that lasts from 15ꢀs to 60ꢀs after the master initiates the
write time slot. If the bus is high during the sampling window, a 1 is written to the DS1825. If the line is low, a 0 is
written to the DS1825.
16 of 21
Figure 15. READ/WRITE TDIMS1E82S5 LPrOogTramTmIMabIlNe RGesDoluIAtioGn 1R-WAirMe Digital Thermometer With 4-Bit ID
START
START
OF SLOT
OF SLOT
MASTER WRITE “0” SLOT
MASTER WRITE “1” SLOT
1 ꢀs < TREC < A
60 ꢀs < TX “0” < 120 ꢀs
> 1 ꢀs
VPU
1-WIRE BUS
GND
DS1825 Samples
DS1825 Samples
MIN
TYP
MAX
MIN
TYP
MAX
15 ꢀs
15 ꢀs
15 ꢀs
15 ꢀs
30 ꢀs
30 ꢀs
MASTER READ “0” SLOT
MASTER READ “1” SLOT
1 ꢀs < TREC < A
VPU
1-WIRE BUS
GND
> 1 ꢀs
Master samples
Master samples
> 1 ꢀs
15 ꢀs
45 ꢀs
15 ꢀs
LINE TYPE LEGEND
Bus master pulling low
DS1825 pulling low
Resistor pullup
READ TIME SLOTS
The DS1825 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 DS1825 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 DS1825 FUNCTION COMMAND section.
All read time slots must be a minimum of 60ꢀs in duration with a minimum of a 1ꢀs recovery time between slots. A
read time slot is initiated by the master device pulling the 1-Wire bus low for a minimum of 1ꢀs and then releasing
the bus (see Figure 14). After the master initiates the read time slot, the DS1825 will begin transmitting a 1 or 0 on
bus. The DS1825 transmits a 1 by leaving the bus high and transmits a 0 by pulling the bus low. When transmitting
a 0, the DS1825 will release the bus by the end of the time slot, and the bus will be pulled back to its high idle state
by the pullup resister. Output data from the DS1825 is valid for 15ꢀs after the falling edge that initiated the read
time slot. Therefore, the master must release the bus and then sample the bus state within 15ꢀs from the start of
the slot.
Figure 15 illustrates that the sum of TINIT, TRC, and TSAMPLE must be less than 15ꢀs for a read time slot. Figure 16
shows that system timing margin is maximized by keeping TINIT and TRC as short as possible and by locating the
master sample time during read time slots towards the end of the 15ꢀs period.
17 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
Figure 16. DETAILED MASTER READ 1 TIMING
VPU
VIH of Master
1-WIRE BUS
GND
Master samples
TINT > 1 ꢀs
TRC
15 ꢀs
Figure 17. RECOMMENDED MASTER READ 1 TIMING
VPU
VIH of Master
1-WIRE BUS
GND
Master samples
TINT
= TRC =
small small
15 ꢀs
LINE TYPE LEGEND
Bus master pulling low
Resistor pullup
DS1825 OPERATION EXAMPLE
In this example there are multiple DS1825s on the bus and they are using parasite power. The bus master initiates
a temperature conversion in a specific DS1825 and then reads its scratchpad and recalculates the CRC to verify
the data.
MASTER MODE
DATA (LSB FIRST)
Reset
COMMENTS
TX
RX
Master issues reset pulse.
Presence
DS1825s respond with presence pulse.
Master issues Search ROM command and builds
Crossreference Table
TX
F0h
TX
RX
TX
TX
TX
Reset
Presence
55h
Master issues reset pulse.
DS1825s respond with presence pulse.
Master issues Match ROM command for desired address
Master sends DS1825 ROM code.
64-bit ROM code
44h
Master issues Convert T command.
DQ line held high by
strong pullup
Reset
Master applies strong pullup to DQ for the duration of the
conversion (tconv).
TX
TX
RX
TX
TX
TX
Master issues reset pulse.
Presence
55h
DS1825s respond with presence pulse.
Master issues Match ROM command.
Master sends DS1825 ROM code.
64-bit ROM code
BEh
Master issues Read Scratchpad command.
Master reads entire scratchpad including CRC. The master
then recalculates the CRC of the first eight data bytes from the
scratchpad and compares the calculated CRC with the read
CRC (byte 9). If they match, the master continues; if not, the
read operation is repeated.
RX
9 data bytes
18 of 21
Figure 18. TYPICAL PERFDOSR18M25APNroCgraEmCmaUblRe VReEsolution 1-Wire Digital Thermometer With 4-Bit ID
1
+3σ
0
-3σ
-1
-10
0
10
20
30
40
50
60
70
80
Temperature, Degrees Centigrade
Figure 19. TIMING DIAGRAMS
19 of 21
DS1825 Programmable Resolution 1-Wire Digital Thermometer With 4-Bit ID
Figure 20. ADDRESS PROGRAMMING DIAGRAM, VDD POWERED
Location 0
1-Wire Bus
DQ
AD0
AD1
AD2
AD3
ADO = GND
AD1 = GND
AD2 = GND
AD3 = GND
VDD
VDD
GND
VDD
Location 1
DQ
AD0
AD1
AD2
AD3
ADO = VDD
AD1 = GND
AD2 = GND
AD3 = GND
VDD
GND
VDD
Location 2
DQ
AD0
AD1
AD2
AD3
ADO = GND
AD1 = VDD
AD2 = GND
AD3 = GND
VDD
GND
VDD
Location 15
DQ
AD0
AD1
AD2
AD3
ADO = VDD
AD1 = VDD
AD2 = VDD
AD3 = VDD
VDD
GND
Note: AD0-AD3 cannot float, each pin must be tied to either VDD or GND.
20 of 21
Figure 21. ADDRESS PRODGSR18A25MPMrogIrNamGmDabIleARGeRsoAlutMion,1P-WAirRe ADigSitIaTl TEhePrmOomWeEterRWEitDh 4-Bit ID
Location 0
1-Wire Bus
DQ
AD0
AD1
AD2
AD3
ADO = GND
AD1 = GND
AD2 = GND
AD3 = GND
VDD
GND
Location 1
DQ
AD0
AD1
AD2
AD3
ADO = VDD
AD1 = GND
AD2 = GND
AD3 = GND
VDD
GND
Location 2
DQ
AD0
AD1
AD2
AD3
ADO = GND
AD1 = VDD
AD2 = GND
AD3 = GND
VDD
GND
Location 15
DQ
AD0
AD1
AD2
AD3
ADO = VDD
AD1 = VDD
AD2 = VDD
AD3 = VDD
VDD
GND
Note: AD0-AD3 cannot float, each pin must be tied to either VDD or GND.
21 of 21
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