MAXIM DS2482

19-4930; Rev 9; 1/12
Single-Channel 1-Wire Master
The DS2482-100 is an I2C-to-1-Wire® bridge device
that interfaces directly to standard (100kHz max) or fast
(400kHz max) I2C masters to perform bidirectional protocol conversion between the I 2 C master and any
downstream 1-Wire slave devices. Relative to any
attached 1-Wire slave device, the DS2482-100 is a
1-Wire master. Internal, factory-trimmed timers relieve
the system host processor from generating time-critical
1-Wire waveforms, supporting both standard and overdrive 1-Wire communication speeds. To optimize
1-Wire waveform generation, the DS2482-100 performs
slew-rate control on rising and falling 1-Wire edges and
provides additional programmable features to match
drive characteristics to the 1-Wire slave environment.
Programmable, strong pullup features support 1-Wire
power delivery to 1-Wire devices such as EEPROMs
and sensors. The DS2482-100 combines these features
with an output to control an external MOSFET for
enhanced strong pullup application. The I 2 C slave
address assignment is controlled by two binary
address inputs, resolving potential conflicts with other
I2C slave devices in the system.
Features
♦ I2C Host Interface Supports 100kHz and 400kHz
I2C Communication Speeds
♦ 1-Wire Master IO with Selectable Active or
Passive 1-Wire Pullup
♦ Provides Reset/Presence, 8-Bit, Single-Bit, and
3-Bit 1-Wire IO Sequences
♦ Standard and Overdrive 1-Wire Communication
Speeds
♦ Slew-Controlled 1-Wire Edges
♦ Strong 1-Wire Pullup Provided by an Internal LowImpedance Signal Path
♦ PCTLZ Output to Optionally Control an External
MOSFET for Stronger Pullup Requirements
♦ Two Address Inputs for I2C Address Assignment
♦ Operating Range: 2.9V to 5.5V, -40°C to +85°C
♦ 8-Pin (150 mils) SO and 9-Bump WLP Packages
Applications
Printers
Medical Instruments
Industrial Sensors
Cell Phones, PDAs
Ordering Information
PART
Pin Configurations appear at end of data sheet.
TEMP RANGE
PIN-PACKAGE
DS2482S-100+
-40°C to +85°C
8 SO (150 mils)
DS2482S-100+T&R
-40°C to +85°C
8 SO (150 mils)
DS2482X-100+T
-40°C to +85°C
9 WLP (2.5k pieces)
+Denotes a lead(Pb)-free/RoHS-compliant package.
T/T&R = Tape and reel.
Typical Operating Circuit
VCC
CURRENT-LIMITING
RESISTOR
REFER TO APPLICATION
NOTE 4206
RP*
(I2C PORT)
μC
SDA
SCL
PCTLZ
OPTIONAL
CIRCUITRY
DS2482-100
AD0
AD1
1-Wire LINE
IO
1-Wire
DEVICE
1-Wire
DEVICE
1-Wire
DEVICE
*RP = I2C PULLUP RESISTOR (SEE THE APPLICATIONS INFORMATION SECTION FOR RP SIZING).
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
DS2482-100
General Description
DS2482-100
Single-Channel 1-Wire Master
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground.........-0.5V to +6V
Maximum Current into Any Pin .........................................±20mA
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-55°C to +125°C
Lead Temperature (SO only; soldering, 10s)...................+300°C
Soldering Temperature (reflow)
SO, WLP.......................................................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = 2.9V to 5.5V, TA = -40°C to +85°C.)
PARAMETER
SYMBOL
Supply Voltage
VCC
Operating Current
ICC
1-Wire Input High (Notes 2, 3)
VIH1
1-Wire Input Low (Notes 2, 3)
VIL1
1-Wire Weak Pullup Resistor
RWPU
1-Wire Output Low
VOL1
Active Pullup On Time
(Notes 4, 5)
Strong Pullup Voltage Drop
tAPUOT
VSTRPU
CONDITIONS
MIN
TYP
MAX
3.3V
2.9
3.3
3.7
5V
4.5
5.0
5.5
(Note 1)
1.9
5V
3.4
0.9
5V
1.2
(Note 4)
PDSRC
Pullup Slew Rate (Note 6)
PUSRC
Power-On Reset Trip Point
VPOR
V
mA
V
3.3V
1000
At 4mA load
V
1675
0.4
V
Standard
2.3
2.5
2.7
Overdrive
0.4
0.5
0.6
VCC 3.2V, 1.5mA load
0.3
VCC 5.2V, 3mA load
0.5
Standard (3.3V ±10%)
Pulldown Slew Rate (Note 6)
0.75
3.3V
UNITS
1
4.2
Overdrive (3.3V ±10%)
5
22.1
Standard (5.0V ±10%)
2
6.5
Overdrive (5.0V ±10%)
10
40
Standard (3.3V ±10%)
0.8
4
Overdrive (3.3V ±10%)
2.7
20
Standard (5.0V ±10%)
1.3
6
Overdrive (5.0V ±10%)
3.4
μs
V
V/μs
V/μs
31
2.2
V
1-Wire TIMING (Note 5) (See Figures 4, 5, and 6)
Write-One/Read Low Time
tW1L
Read Sample Time
tMSR
1-Wire Time Slot
t SLOT
2
Standard
7.6
8
8.4
Overdrive
0.9
1
1.1
Standard
13.3
14
15
Overdrive
1.4
1.5
1.8
Standard
65.8
69.3
72.8
Overdrive
9.9
10.5
11.0
_______________________________________________________________________________________
μs
μs
μs
Single-Channel 1-Wire Master
(VCC = 2.9V to 5.5V, TA = -40°C to +85°C.)
PARAMETER
SYMBOL
CONDITIONS
Standard (3.3V to 0V)
Fall Time High-to-Low
(Notes 6, 7)
Write-Zero Low Time
tF1
tW0L
Write-Zero Recovery Time
tREC0
Reset Low Time
tRSTL
Presence-Detect Sample Time
tMSP
Sampling for Short and Interrupt
tSI
Reset High Time
tRSTH
MIN
TYP
MAX
0.54
3.0
Overdrive (3.3V to 0V)
0.10
0.59
Standard (5.0V to 0V)
0.55
2.2
Overdrive (5.0V to 0V)
0.09
0.44
Standard
60
64
68
Overdrive
7.1
7.5
7.9
Standard
5.0
5.3
5.6
Overdrive
2.8
3.0
3.2
Standard
570
600
630
Overdrive
68.4
72
75.6
Standard
66.5
70
73.5
Overdrive
7.1
7.5
7.9
Standard
7.6
8
8.4
Overdrive
0.7
0.75
0.8
Standard
554.8
584
613.2
Overdrive
70.3
74
77.7
UNITS
μs
μs
μs
μs
μs
μs
μs
CONTROL PIN (PCTLZ)
Output Low Voltage
VOLP
VCC = 2.9V, 1.2mA load current
Output High Voltage
VOHP
0.4mA load current
0.4
VCC 0.5V
V
V
I2C PINS (SCL, SDA, AD0, AD1) (Note 8) (See Figure 9)
VCC = 2.9V to 3.7V
-0.5
0.25 ×
VCC
VCC = 4.5V to 5.5V
-0.5
0.22 ×
VCC
VIH
0.7 ×
VCC
VCC +
0.5V
Hysteresis of Schmitt Trigger
Inputs
VHYS
0.05 ×
VCC
Low-Level Output Voltage at
3mA Sink Current
VOL
Output Fall Time from VIH(MIN) to
VIL(MAX) with a Bus Capacitance
from 10pF to 400pF
t OF
Pulse Width of Spikes That Are
Suppressed by the Input Filter
t SP
Input Current Each Input/Output
Pin with an Input Voltage
Between 0.1 x VCC(MAX) and
0.9 x VCC(MAX)
II
Low-Level Input Voltage
High-Level Input Voltage
VIL
60
SDA and SCL pins only
(Notes 9, 10)
-10
V
V
V
0.4
V
250
ns
50
ns
+10
μA
_______________________________________________________________________________________
3
DS2482-100
ELECTRICAL CHARACTERISTICS (continued)
DS2482-100
Single-Channel 1-Wire Master
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 2.9V to 5.5V, TA = -40°C to +85°C.)
PARAMETER
Input Capacitance
SCL Clock Frequency
Hold Time (Repeated) START
Condition (After this period, the
first clock pulse is generated.)
SYMBOL
CI
CONDITIONS
MIN
TYP
(Note 9)
f SCL
0
tHD:STA
0.6
MAX
UNITS
10
pF
400
kHz
μs
Low Period of the SCL Clock
tLOW
1.3
μs
High Period of the SCL Clock
tHIGH
0.6
μs
Setup Time for a Repeated
START Condition
t SU:STA
0.6
μs
Data Hold Time
tHD:DAT
(Notes 11, 12)
Data Setup Time
t SU:DAT
(Note 13)
250
ns
Setup Time for STOP Condition
t SU:STO
0.6
μs
Bus Free Time Between a STOP
and START Condition
tBUF
1.3
μs
Capacitive Load for Each Bus
Line
CB
(Note 14)
400
pF
t OSCWUP
(Note 15)
100
μs
Oscillator Warmup Time
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
Note 15:
4
0.9
μs
Operating current with 1-Wire write-byte sequence followed by continuously reading the Status Register at 400kHz in overdrive.
With standard speed, the total capacitive load of the 1-Wire bus should not exceed 1nF. Otherwise, the passive pullup on
threshold VIL1 may not be reached in the available time. With overdrive speed, the capacitive load on the 1-Wire bus must
not exceed 300pF.
Active pullup guaranteed to turn on between VIL1(MAX) and VIH1(MIN).
Active or resistive pullup choice is configurable.
Except for tF1, all 1-Wire timing specifications and tAPUOT are derived from the same timing circuit. Therefore, if one of
these parameters is found to be off the typical value, it is safe to assume that all these parameters deviate from their typical value in the same direction and by the same degree.
These values apply at full load, i.e., 1nF at standard speed and 0.3nF at overdrive speed. For reduced load, the pulldown
slew rate is slightly faster.
Fall time high-to-low (tF1) is derived from PDSRC, referenced from 0.9 x VCC to 0.1 x VCC.
All I2C timing values are referred to VIH(MIN) and VIL(MAX) levels.
Applies to SDA, SCL, AD0 and AD1.
The input/output pins of the DS2482-100 do not obstruct the SDA and SCL lines if VCC is switched off.
The DS2482-100 provides a hold time of at least 300ns for the SDA signal (referred to the VIH(MIN) of the SCL signal) to
bridge the undefined region of the falling edge of SCL.
The maximum tHD:DAT need only be met if the device does not stretch the low period (tLOW) of the SCL signal.
A fast-mode I2C bus device can be used in a standard-mode I2C bus system, but the requirement tSU:DAT ≥ 250ns must
then be met. This is automatically the case if the device does not stretch the low period of the SCL signal. If such a device
does stretch the low period of the SCL signal, it must output the next data bit to the SDA line tR(MAX) + tSU:DAT = 1000 +
250 = 1250ns (according to the standard-mode I2C bus specification) before the SCL line is released.
CB—Total capacitance of one bus line in pF. If mixed with high-speed-mode devices, faster fall times according to I2CBus Specification Version 2.1 are allowed.
I2C communication should not take place for the max tOSCWUP time following a power-on reset.
_______________________________________________________________________________________
Single-Channel 1-Wire Master
PIN
SO
WLP
1
B3
NAME
VCC
FUNCTION
Power-Supply Input
2
C3
IO
3
C2
GND
Input/Output Driver for 1-Wire Line
Ground Reference
4
B1
SCL
I2C Serial Clock Input. Must be connected to VCC through a pullup resistor.
5
B2
SDA
I2C Serial Data Input/Output. Must be connected to VCC through a pullup resistor.
6
A1
PCTLZ
7
A2
AD1
8
A3
AD0
Active-Low Control Output for an External p-Channel MOSFET. Provides extra power to the 1-Wire
line, e.g., for use with 1-Wire devices that require a higher current temporarily to operate.
I2C Address Inputs. Must be connected to VCC or GND. These inputs determine the I2C slave
address of the device (see Figure 8).
CONFIGURATION
REGISTER
SDA
SCL
I2C
INTERFACE
CONTROLLER
T-TIME OSC
INPUT/OUTPUT
CONTROLLER
AD0
AD1
LINE
XCVR
IO
PCTLZ
STATUS
REGISTER
READ DATA
REGISTER
DS2482-100
Figure 1. Block Diagram
Detailed Description
The DS2482-100 is a self-timed 1-Wire master that supports advanced 1-Wire waveform features including
standard and overdrive speeds, active pullup, and
strong pullup for power delivery. The active pullup
affects rising edges on the 1-Wire side. The strong
pullup function uses the same pullup transistor as the
active pullup, but with a different control algorithm. In
addition, the strong pullup activates the PCTLZ pin,
controlling optional external circuitry to deliver additional power beyond the capabilities of the on-chip pullup
transistor. Once supplied with command and data, the
input/output controller of the DS2482-100 performs
time-critical 1-Wire communication functions such as
reset/presence-detect cycle, read-byte, write-byte, single-bit R/W, and triplet for ROM Search, without requiring interaction with the host processor. The host obtains
feedback (completion of a 1-Wire function, presence
pulse, 1-Wire short, search direction taken) through the
Status Register and data through the Read Data
Register. The DS2482-100 communicates with a host
processor through its I 2C bus interface in standard
mode or in fast mode. The logic state of two address pins
determines the I2C slave address of the DS2482-100,
allowing up to four devices operating on the same bus
segment without requiring a hub. See Figure 1 for a block
diagram.
_______________________________________________________________________________________
5
DS2482-100
Pin Description
DS2482-100
Single-Channel 1-Wire Master
Device Registers
The DS2482-100 has three registers that the I2C host
can read: Configuration, Status, and Read Data. These
registers are addressed by a read pointer. The position
of the read pointer, i.e., the register that the host reads
in a subsequent read access, is defined by the instruction the DS2482-100 executed last. To enable certain
1-Wire features, the host has read and write access to
the Configuration Register.
Configuration Register
The DS2482-100 supports three 1-Wire features that
are enabled or selected through the Configuration
Register. These features are:
• Active Pullup (APU)
• Strong Pullup (SPU)
• 1-Wire Speed (1WS)
These features can be selected in any combination.
While APU and 1WS maintain their state, SPU returns to
its inactive state as soon as the strong pullup has ended.
After a device reset (power-up cycle or initiated by the
Device Reset command), the Configuration Register
reads 00h. When writing to the Configuration Register,
the new data is accepted only if the upper nibble (bits 7
to 4) is the one’s complement of the lower nibble (bits 3
to 0). When read, the upper nibble is always 0h.
Active Pullup (APU)
The APU bit controls whether an active pullup (controlled slew-rate transistor) or a passive pullup (RWPU
resistor) is used to drive a 1-Wire line from low to high.
When APU = 0, active pullup is disabled (resistor
mode). Active pullup should always be selected unless
there is only a single slave on the 1-Wire line. The
active pullup does not apply to the rising edge of a
presence pulse or a recovery after a short on the
1-Wire line.
The circuit that controls rising edges (Figure 2) operates as follows: At t1, the pulldown (from DS2482-100
or 1-Wire slave) ends. From this point on, the 1-Wire
bus is pulled high through R WPU internal to the
DS2482-100. VCC and the capacitive load of the 1-Wire
line determine the slope. In case that active pullup is
disabled (APU = 0), the resistive pullup continues, as
represented by the solid line. With active pullup
enabled (APU = 1), and when at t2 the voltage has
reached a level between VIL1(MAX) and VIH1(MIN), the
DS2482-100 actively pulls the 1-Wire line high, applying
a controlled slew rate as represented by the dashed
line. The active pullup continues until tAPUOT is expired
at t3. From that time on the resistive pullup continues.
See the Strong Pullup (SPU) section for a way to keep
the pullup transistor conducting beyond t3.
Configuration Register Bit Assignment
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
1WS
SPU
1
APU
1WS
SPU
0
APU
VCC
APU = 1
APU = 0
VIH1(MIN)
VIL1(MAX)
0V
tAPUOT
1-Wire BUS IS DISCHARGED
t1
t2
t3
Figure 2. Rising Edge Pullup
6
_______________________________________________________________________________________
Single-Channel 1-Wire Master
long as the strong pullup is active, the PCTLZ output is low.
When the strong pullup ends, the SPU bit is automatically reset to 0. Using the strong pullup feature does
not change the state of the APU bit in the Configuration
Register. Note: Strong pullup also affects the 1-Wire
Reset command. If enabled, it can cause incorrect
reading of the presence pulse and may cause a violation of the device’s absolute maximum rating.
1-Wire Speed (1WS)
The 1WS bit determines the timing of any 1-Wire communication generated by the DS2482-100. All 1-Wire
slave devices support standard speed (1WS = 0),
where the transfer of a single bit (tSLOT in Figure 3) is
completed within 65µs. Many 1-Wire devices can also
communicate at a higher data rate, called overdrive
speed. To change from standard to overdrive speed, a
1-Wire device needs to receive an Overdrive-Skip ROM
or Overdrive-Match ROM command, as explained in
the 1-Wire device data sheets. The change in speed
occurs immediately after the 1-Wire device has
received the speed-changing command code. The
DS2482-100 must take part in this speed change to
stay synchronized. This is accomplished by writing to
the Configuration Register with the 1WS bit as 1 immediately after the 1-Wire Byte command that changes the
speed of a 1-Wire device. Writing to the Configuration
Register with the 1WS bit as 0, followed by a 1-Wire
Reset command, changes the DS2482-100 and any
1-Wire devices on the active 1-Wire line back to standard speed.
LAST BIT OF 1-Wire WRITE BYTE OR 1-Wire SINGLE BIT FUNCTION
VCC
WRITE-ONE CASE
WRITE-ZERO CASE
NEXT
TIME SLOT
OR 1-Wire
RESET
0V
tSLOT
PCTLZ
DS2482-100 RESISTIVE PULLUP
DS2482-100 PULLDOWN
DS2482-100 STRONG PULLUP
Figure 3. Low-Impedance Pullup Timing
_______________________________________________________________________________________
7
DS2482-100
Strong Pullup (SPU)
The SPU bit is used to activate the strong pullup function prior to a 1-Wire Write Byte or 1-Wire Single Bit
command. Strong pullup is commonly used with 1-Wire
EEPROM devices when copying scratchpad data to the
main memory or when performing an SHA-1 computation and with parasitically powered temperature sensors or A/D converters. The respective device data
sheets specify the location in the communications protocol after which the strong pullup should be applied.
The SPU bit must be set immediately prior to issuing
the command that puts the 1-Wire device into the state
where it needs the extra power. The strong pullup uses
the same internal pullup transistor as the active pullup
feature. For cases where the internal strong pullup has
insufficient strength, the PCTLZ pin can be used to control an external p-channel MOSFET to supply additional
power beyond the drive capability of the DS2482-100 to
the 1-Wire line. See the ΔV STRPU parameter in the
Electrical Characteristics to determine if the internal
strong pullup is sufficient given the current load on the
device.
If SPU is 1, the DS2482-100 treats the rising edge of the
time slot in which the strong pullup starts as if the active
pullup was activated. However, in contrast to the active
pullup, the strong pullup, i.e., the internal pullup transistor,
remains conducting, as shown in Figure 3, until one of
three events occurs: the DS2482-100 receives a command
that generates 1-Wire communication (the typical case);
the SPU bit in the Configuration Register is written to 0; or
the DS2482-100 receives the Device Reset command. As
DS2482-100
Single-Channel 1-Wire Master
Status Register Bit Assignment
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
DIR
TSB
SBR
RST
LL
SD
PPD
1WB
Status Register
The read-only Status Register is the general means for
the DS2482-100 to report bit-type data from the 1-Wire
side, 1-Wire busy status, and its own reset status to the
host processor. All 1-Wire communication commands
and the Device Reset command position the read
pointer at the Status Register for the host processor to
read with minimal protocol overhead. Status information
is updated during the execution of certain commands
only. Details are given in the description of the various
status bits that follow.
1-Wire Busy (1WB)
The 1WB bit reports to the host processor whether the
1-Wire line is busy. During 1-Wire communication 1WB
is 1; once the command is completed, 1WB returns to
its default 0. Details on when 1WB changes state and
for how long it remains at 1 are found in the Function
Commands section.
Presence-Pulse Detect (PPD)
The PPD bit is updated with every 1-Wire Reset command. If the DS2482-100 detects a presence pulse from
a 1-Wire device at tMSP during the presence-detect
cycle, the PPD bit is set to 1. This bit returns to its default
0 if there is no presence pulse or if the 1-Wire line is
shorted during a subsequent 1-Wire Reset command.
Short Detected (SD)
The SD bit is updated with every 1-Wire Reset command. If the DS2482-100 detects a logic 0 on the
1-Wire line at tSI during the presence-detect cycle, the
SD bit is set to 1. This bit returns to its default 0 with a
subsequent 1-Wire Reset command provided that the
short has been removed. If SD is 1, PPD is 0. The
DS2482-100 cannot distinguish between a short and a
DS1994 or DS2404 signaling a 1-Wire interrupt. For this
reason, if a DS2404 or DS1994 is used in the application, the interrupt function must be disabled. The interrupt signaling is explained in the respective 1-Wire
device data sheets.
8
Logic Level (LL)
The LL bit reports the logic state of the active 1-Wire
line without initiating any 1-Wire communication. The
1-Wire line is sampled for this purpose every time the
Status Register is read. The sampling and updating of
the LL bit takes place when the host processor has
addressed the DS2482-100 in read mode (during the
acknowledge cycle), provided that the read pointer is
positioned at the Status Register.
Device Reset (RST)
If the RST bit is 1, the DS2482-100 has performed an
internal reset cycle, either caused by a power-on reset
or from executing the Device Reset command. The RST
bit is cleared automatically when the DS2482-100 executes a Write Configuration command to restore the
selection of the desired 1-Wire features.
Single Bit Result (SBR)
The SBR bit reports the logic state of the active 1-Wire line
sampled at tMSR of a 1-Wire Single Bit command or the
first bit of a 1-Wire Triplet command. The power-on default
of SBR is 0. If the 1-Wire Single Bit command sends a 0
bit, SBR should be 0. With a 1-Wire Triplet command,
SBR could be 0 as well as 1, depending on the response
of the 1-Wire devices connected. The same result applies
to a 1-Wire Single Bit command that sends a 1 bit.
Triplet Second Bit (TSB)
The TSB bit reports the logic state of the active 1-Wire
line sampled at t MSR of the second bit of a 1-Wire
Triplet command. The power-on default of TSB is 0.
This bit is updated only with a 1-Wire Triplet command
and has no function with other commands.
Branch Direction Taken (DIR)
Whenever a 1-Wire Triplet command is executed, this
bit reports to the host processor the search direction
that was chosen by the third bit of the triplet. The
power-on default of DIR is 0. This bit is updated only
with a 1-Wire Triplet command and has no function with
other commands. For additional information, see the
description of the 1-Wire Triplet command and
Application Note 187: 1-Wire Search Algorithm.
_______________________________________________________________________________________
Single-Channel 1-Wire Master
The DS2482-100 understands eight function commands that fall into four categories: device control, I2C
communication, 1-Wire setup, and 1-Wire communication. The feedback path to the host is controlled by a
read pointer, which is set automatically by each function command for the host to efficiently access relevant
information. The host processor sends these commands and applicable parameters as strings of one or
two bytes using the I 2C interface. The I 2C protocol
requires that each byte be acknowledged by the
receiving party to confirm acceptance or not be
acknowledged to indicate an error condition (invalid
code or parameter) or to end the communication. See
the I2C Interface section for details of the I2C protocol
including acknowledge.
The function commands are as follows:
1) Device Reset
2) Set Read Pointer
3) Write Configuration
4) 1-Wire Reset
DS2482-100
Function Commands
5) 1-Wire Single Bit
6) 1-Wire Write Byte
7) 1-Wire Read Byte
8) 1-Wire Triplet
Table 1. Valid Pointer Codes
REGISTER SELECTION
CODE
Status Register
F0h
Read Data Register
E1h
Configuration Register
C3h
Device Reset
Command Code
F0h
Command Parameter
None
Description
Performs a global reset of device state machine logic. Terminates any ongoing 1-Wire
communication.
Typical Use
Device initialization after power-up; reinitialization (reset) as desired.
Restriction
None (can be executed at any time).
Error Response
None
Command Duration
Maximum 525ns. Counted from falling SCL edge of the command code acknowledge bit.
1-Wire Activity
Ends maximum 262.5ns after the falling SCL edge of the command code acknowledge bit.
Read Pointer Position
Status Register (for busy polling).
Status Bits Affected
RST set to 1; 1WB, PPD, SD, SBR, TSB, DIR set to 0.
Configuration Bits Affected
1WS, APU, SPU set to 0.
Set Read Pointer
Command Code
E1h
Command Parameter
Pointer Code (see Table 1)
Description
Sets the read pointer to the specified register. Overwrites the read pointer position of any 1-Wire
communication command in progress.
Typical Use
To prepare reading the result from a 1-Wire Read Byte command; random read access of
registers.
Restriction
None (can be executed at any time).
Error Response
If the pointer code is not valid, the pointer code is not acknowledged and the command is
ignored.
Command Duration
None. The read pointer is updated on the rising SCL edge of the pointer code acknowledge bit.
1-Wire Activity
Not affected.
Read Pointer Position
As specified by the pointer code.
Status Bits Affected
None
Configuration Bits Affected
None
_______________________________________________________________________________________
9
DS2482-100
Single-Channel 1-Wire Master
Write Configuration
Command Code
D2h
Command Parameter
Configuration Byte
Description
Writes a new configuration byte. The new settings take effect immediately. Note: When writing to
the Configuration Register, the new data is accepted only if the upper nibble (bits 7 to 4) is the
one’s complement of the lower nibble (bits 3 to 0). When read, the upper nibble is always 0h.
Typical Use
Defining the features for subsequent 1-Wire communication.
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command.
Error Response
Command code and parameter are not acknowledged if 1WB = 1 at the time the command code
is received and the command is ignored.
Command Duration
None. The Configuration Register is updated on the rising SCL edge of the configuration-byte
acknowledge bit.
1-Wire Activity
None
Read Pointer Position
Configuration Register (to verify write).
Status Bits Affected
RST set to 0.
Configuration Bits Affected
1WS, SPU, APU updated.
1-Wire Reset
Command Code
B4h
Command Parameter
None
Description
Generates a 1-Wire reset/presence-detect cycle (Figure 4) at the 1-Wire line. The state of the
1-Wire line is sampled at t SI and tMSP and the result is reported to the host processor through the
Status Register, bits PPD and SD.
Typical Use
To initiate or end any 1-Wire communication sequence.
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command. Strong
pullup (see the SPU bit) should not be used in conjunction with the 1-Wire Reset command. If SPU
is enabled, the PPD bit may not be valid and may cause a violation of the device’s absolute
maximum rating.
Error Response
Command code is not acknowledged if 1WB = 1 at the time the command code is received and
the command is ignored.
Command Duration
tRSTL + tRSTH + maximum 262.5ns, counted from the falling SCL edge of the command code
acknowledge bit.
1-Wire Activity
Begins maximum 262.5ns after the falling SCL edge of the command code acknowledge bit.
Read Pointer Position
Status Register (for busy polling).
Status Bits Affected
1WB (set to 1 for tRSTL + tRSTH), PPD is updated at tRSTL + tMSP, SD is updated at tRSTL + t SI .
Configuration Bits Affected
1WS, APU, SPU apply.
10
______________________________________________________________________________________
Single-Channel 1-Wire Master
Command Code
87h
Command Parameter
Bit Byte
Description
Generates a single 1-Wire time slot with a bit value “V” as specified by the bit byte at the 1-Wire
line (see Table 2). A V value of 0b generates a write-zero time slot (Figure 5); a V value of 1b
generates a write-one time slot, which also functions as a read-data time slot (Figure 6). In either
case, the logic level at the 1-Wire line is tested at tMSR and SBR is updated.
Typical Use
To perform single-bit writes or reads at the 1-Wire line when single bit communication is
necessary (the exception).
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command.
Error Response
Command code and bit byte are not acknowledged if 1WB = 1 at the time the command code is
received and the command is ignored.
Command Duration
t SLOT + maximum 262.5ns, counted from the falling SCL edge of the first bit (MSB) of the bit byte.
1-Wire Activity
Begins maximum 262.5ns after the falling SCL edge of the MSB of the bit byte.
Read Pointer Position
Status Register (for busy polling and data reading).
Status Bits Affected
1WB (set to 1 for t SLOT), SBR is updated at tMSR , DIR (may change its state).
1WS, APU, SPU apply.
Configuration Bits Affected
Table 2. Bit Allocation in the Bit Byte
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
V
x
x
x
x
x
x
x
x = Don’t care.
RESET PULSE
PRESENCE/SHORT DETECT
tMSP
tSI
VCC
PRESENCE PULSE
APU CONTROLLED
EDGE
VIH1
VIL1
RESISTIVE PULLUP
0V
tF1
tRSTL
PULLUP
tRSTH
DS2482-100 PULLDOWN
1-Wire SLAVE PULLDOWN
Figure 4. 1-Wire Reset/Presence-Detect Cycle
______________________________________________________________________________________
11
DS2482-100
1-Wire Single Bit
DS2482-100
Single-Channel 1-Wire Master
tWOL
tMSR
VCC
VIH1
VIL1
0V
tF1
tREC0
tSLOT
PULLUP (SEE FIGURE 2)
DS2482-100 PULLDOWN
Figure 5. Write-Zero Time Slot
tMSR
tW1L
VCC
VIH1
VIL1
0V
tF1
tSLOT
PULLUP (SEE FIGURE 2)
DS2482-100 PULLDOWN
1-Wire SLAVE PULLDOWN
NOTE: DEPENDING ON ITS INTERNAL STATE, A 1-Wire SLAVE DEVICE TRANSMITS DATA TO ITS MASTER (e.g. THE DS2482-100). WHEN RESPONDING WITH A 0,
A 1-Wire SLAVE STARTS PULLING THE LINE LOW DURING tW1L. ITS INTERNAL TIMING GENERATOR DETERMINES WHEN THIS PULLDOWN ENDS AND THE VOLTAGE
STARTS RISING AGAIN. WHEN RESPONDING WITH A 1, A 1-Wire SLAVE DOES NOT HOLD THE LINE LOW AT ALL, AND THE VOLTAGE STARTS RISING AS SOON AS tW1L
IS OVER. 1-Wire DEVICE DATA SHEETS USE THE TERM tRL INSTEAD OF tW1L TO DESCRIBE A READ-DATA TIME SLOT. TECHNICALLY, tRL AND tW1L HAVE IDENTICAL
SPECIFICATIONS AND CANNOT BE DISTINGUISHED FROM EACH OTHER.
Figure 6. Write-One and Read-Data Time Slot
12
______________________________________________________________________________________
Single-Channel 1-Wire Master
Command Code
A5h
Command Parameter
Data Byte
Description
Writes a single data byte to the 1-Wire line.
Typical Use
To write commands or data to the 1-Wire line. Equivalent to executing eight 1-Wire Single Bit
commands, but faster due to less I2C traffic.
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command.
Error Response
Command code and data byte are not acknowledged if 1WB = 1 at the time the command code is
received and the command is ignored.
Command Duration
8 x t SLOT + maximum 262.5ns, counted from falling edge of the last bit (LSB) of the data byte.
1-Wire Activity
Begins maximum 262.5ns after falling SCL edge of the LSB of the data byte (i.e., before the data
byte acknowledge). Note: The bit order on the I2C bus and the 1-Wire line is different (1-Wire: LSB
first; I2C: MSB first). Therefore, 1-Wire activity cannot begin before the DS2482-100 has received
the full data byte.
Read Pointer Position
Status Register (for busy polling).
Status Bits Affected
1WB (set to 1 for 8 x t SLOT).
1WS, SPU, APU apply.
Configuration Bits Affected
1-Wire Read Byte
Command Code
96h
Command Parameter
None
Description
Generates eight read-data time slots on the 1-Wire line and stores result in the Read Data
Register.
Typical Use
To read data from the 1-Wire line. Equivalent to executing eight 1-Wire Single Bit commands with
V = 1 (write-one time slot), but faster due to less I2C traffic.
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command.
Error Response
Command code is not acknowledged if 1WB = 1 at the time the command code is received and
the command is ignored.
Command Duration
8 x t SLOT + maximum 262.5ns, counted from the falling SCL edge of the command code
acknowledge bit.
1-Wire Activity
Begins maximum 262.5ns after the falling SCL edge of the command code acknowledge bit.
Read Pointer Position
Status Register (for busy polling). Note: To read the data byte received from the 1-Wire line, issue
the Set Read Pointer command and select the Read Data Register. Then access the DS2482-100
in read mode.
Status Bits Affected
1WB (set to 1 for 8 x t SLOT).
Configuration Bits Affected
1WS, APU apply.
______________________________________________________________________________________
13
DS2482-100
1-Wire Write Byte
DS2482-100
Single-Channel 1-Wire Master
1-Wire Triplet
Command Code
78h
Command Parameter
Direction Byte
Description
Generates three time slots: two read time slots and one write time slot at the 1-Wire line. The type
of write time slot depends on the result of the read time slots and the direction byte. The direction
byte determines the type of write time slot if both read time slots are 0 (a typical case). In this
case, the DS2482-100 generates a write-one time slot if V = 1 and a write-zero time slot if V = 0.
See Table 3.
If the read time slots are 0 and 1, they are followed by a write-zero time slot.
If the read time slots are 1 and 0, they are followed by a write-one time slot.
If the read time slots are both 1 (error case), the subsequent write time slot is a write-one.
Typical Use
To perform a 1-Wire Search ROM sequence; a full sequence requires this command to be
executed 64 times to identify and address one device.
Restriction
1-Wire activity must have ended before the DS2482-100 can process this command.
Error Response
Command code and direction byte is not acknowledged if 1WB = 1 at the time the command
code is received and the command is ignored.
Command Duration
3 x t SLOT + maximum 262.5ns, counted from the falling SCL edge of the first bit (MSB) of the
direction byte.
1-Wire Activity
Begins maximum 262.5ns after the falling SCL edge of the MSB of the direction byte.
Read Pointer Position
Status Register (for busy polling).
Status Bits Affected
1WB (set to 1 for 3 x t SLOT), SBR is updated at the first tMSR, TSB and DIR are updated at the
second tMSR (i.e., at t SLOT + tMSR).
Configuration Bits Affected
1WS, APU apply.
Table 3. Bit Allocation in the Direction Byte
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
V
x
x
x
x
x
x
x
x = Don’t care.
14
______________________________________________________________________________________
Single-Channel 1-Wire Master
MSB
LSB
MSB
DS2482-100
MSB FIRST
LSB
SDA
SLAVE
ADDRESS
SCL
1–7
IDLE
START
CONDITION
R/W
8
ACK
9
DATA
1–7
ACK
8
DATA
9
ACK/
NACK
1–7
8
9
REPEATED IF MORE BYTES
ARE TRANSFERRED
STOP CONDITION
REPEATED START
Figure 7. I2C Protocol Overview
I2C Interface
transmitted first. After each byte follows an acknowledge
bit to allow synchronization between master and slave.
General Characteristics
The I2C bus uses a data line (SDA) plus a clock signal
(SCL) for communication. Both SDA and SCL are bidirectional lines, connected to a positive supply voltage
through a pullup resistor. When there is no communication, both lines are high. The output stages of devices
connected to the bus must have an open drain or open
collector to perform the wired-AND function. Data on
the I 2 C bus can be transferred at rates of up to
100kbps in standard mode and up to 400kbps in fast
mode. The DS2482-100 works in both modes.
A device that sends data on the bus is defined as a
transmitter, and a device receiving data is defined as a
receiver. The device that controls the communication is
called a master. The devices that are controlled by the
master are slaves. To be individually accessed, each
device must have a slave address that does not conflict
with other devices on the bus.
Data transfers can be initiated only when the bus is not
busy. The master generates the serial clock (SCL), controls the bus access, generates the START and STOP
conditions, and determines the number of data bytes
transferred between START and STOP (Figure 7). Data
is transferred in bytes with the most significant bit being
Slave Address
The slave address to which the DS2482-100 responds
is shown in Figure 8. The logic state at the address pins
AD0 and AD1 determines the value of the address bits
A0 and A1. The address pins allow the device to
respond to one of four possible slave addresses. The
slave address is part of the slave address/control byte.
The last bit of the slave address/control byte (R/W)
defines the data direction. When set to 0, subsequent
data flows from master to slave (write access); when
set to 1, data flows from slave to master (read access).
7-BIT SLAVE ADDRESS
A6
A5
A4
A3
A2
A1
A0
0
0
1
1
0
AD1
AD0
MSB
AD1, AD0
PIN STATES
R/W
DETERMINES
READ OR WRITE
Figure 8. DS2482-100 Slave Address
______________________________________________________________________________________
15
DS2482-100
Single-Channel 1-Wire Master
SDA
tBUF
tF
tSP
tHD:STA
tLOW
SCL
tHIGH
tHD:STA
tHD:DAT
STOP
tSU:STA
tR
SPIKE
SUPPRESSION
tSU:STO
tSU:DAT
START
REPEATED
START
NOTE: TIMING IS REFERENCED TO VIL(MAX) AND VIH(MIN).
Figure 9. I2C Timing Diagram
I2C Definitions
The following terminology is commonly used to
describe I2C data transfers. The timing references are
defined in Figure 9.
Bus Idle or Not Busy: Both SDA and SCL are inactive and in their logic-high states.
START Condition: To initiate communication with a
slave, the master must generate a START condition.
A START condition is defined as a change in state of
SDA from high to low while SCL remains high.
STOP Condition: To end communication with a
slave, the master must generate a STOP condition. A
STOP condition is defined as a change in state of
SDA from low to high while SCL remains high.
Repeated START Condition: Repeated STARTs are
commonly used for read accesses to select a specific data source or address to read from. The master can use a repeated START condition at the end
of a data transfer to immediately initiate a new data
transfer following the current one. A repeated START
condition is generated the same way as a normal
START condition, but without leaving the bus idle
after a STOP condition.
Data Valid: With the exception of the START and
STOP condition, transitions of SDA can occur only
during the low state of SCL. The data on SDA must
remain valid and unchanged during the entire high
pulse of SCL plus the required setup and hold time
(tHD:DAT after the falling edge of SCL and tSU:DAT
16
before the rising edge of SCL; see Figure 9). There
is one clock pulse per bit of data. Data is shifted into
the receiving device during the rising edge of SCL.
When finished with writing, the master must release
the SDA line for a sufficient amount of setup time
(minimum tSU:DAT + tR in Figure 9) before the next
rising edge of SCL to start reading. The slave shifts
out each data bit on SDA at the falling edge of the
previous SCL pulse and the data bit is valid at the
rising edge of the current SCL pulse. The master
generates all SCL clock pulses, including those
needed to read from a slave.
Acknowledge: Typically a receiving device, when
addressed, is obliged to generate an acknowledge
after the receipt of each byte. The master must generate a clock pulse that is associated with this
acknowledge bit. A device that acknowledges must
pull SDA low during the acknowledge clock pulse in
such a way that SDA is stable low during the high
period of the acknowledge-related clock pulse plus
the required setup and hold time (tHD:DAT after the
falling edge of SCL and tSU:DAT before the rising
edge of SCL).
Not Acknowledged by Slave: A slave device may
be unable to receive or transmit data, for example,
because it is busy performing some real-time function. In this case, the slave device does not acknowledge its slave address and leaves the SDA line high.
A slave device that is ready to communicate
acknowledges at least its slave address. However,
______________________________________________________________________________________
Single-Channel 1-Wire Master
Writing to the DS2482-100
To write to the DS2482-100, the master must access
the device in write mode, i.e., the slave address must
be sent with the direction bit set to 0. The next byte to
be sent is a command code, which, depending on the
command, may be followed by a command parameter.
The DS2482-100 acknowledges valid command codes
and expected/valid command parameters. Additional
bytes or invalid command parameters are never
acknowledged.
Reading from the DS2482-100
To read from the DS2482-100, the master must access
the device in read mode, i.e., the slave address must
be sent with the direction bit set to 1. The read pointer
determines the register that the master reads from. The
master can continue reading the same register over
and over again, without having to readdress the device,
e.g., to watch the 1WB changing from 1 to 0. To read
from a different register, the master must issue the Set
Read Pointer command and then access the DS2482100 again in read mode.
I2C Communication Examples
See Tables 4 and 5 for the I2C communication legend
and data direction codes.
Table 4. I2C Communication—Legend
SYMBOL
S
DESCRIPTION
START Condition
AD, 0
Select DS2482-100 for Write Access
AD, 1
Select DS2482-100 for Read Access
Sr
Repeated START Condition
P
STOP Condition
A
Acknowledged
A\
(Idle)
<byte>
DRST
SRP
WCFG
Not Acknowledged
Bus Not Busy
Transfer of One Byte
Command “Device Reset”, F0h
Command “Set Read Pointer”, E1h
Command “Write Configuration”, D2h
1WRS
Command “1-Wire Reset”, B4h
1WSB
Command “1-Wire Single Bit”, 87h
1WWB
Command “1-Wire Write Byte”, A5h
1WRB
Command “1-Wire Read Byte”, 96h
1WT
Command “1-Wire Triplet”, 78h
Table 5. Data Direction Codes
Master-to-Slave
Slave-to-Master
______________________________________________________________________________________
17
DS2482-100
some time later the slave may refuse to accept data,
possibly because of an invalid command code or
parameter. In this case, the slave device does not
acknowledge any of the bytes that it refuses and
leaves SDA high. In either case, after a slave has
failed to acknowledge, the master first should generate a repeated START condition or a STOP condition
followed by a START condition to begin a new data
transfer.
Not Acknowledged by Master: At some time when
receiving data, the master must signal an end of
data to the slave device. To achieve this, the master
does not acknowledge the last byte that it has
received from the slave. In response, the slave
releases SDA, allowing the master to generate the
STOP condition.
DS2482-100
Single-Channel 1-Wire Master
I2C Communication Examples (continued)
Device Reset (After Power-Up)
S
AD,0
A
DRST
A
Sr
AD,1
A
<byte>
A\
P
Activities that are underlined denote an optional read access to verify the success of the command.
Set Read Pointer (To Read from Another Register)
Case A: Valid Read Pointer Code
S
AD,0
A
SRP
A
C3h
A
P
C3h is the valid read pointer code for the Configuration Register.
Case B: Invalid Read Pointer Code
S
AD,0
A
SRP
A
E5h
A\
P
E5h is an invalid read pointer code.
Write Configuration (Before Starting 1-Wire Activity)
Case A: 1-Wire Idle (1WB = 0)
S
AD,0
A
WCFG
A
<byte>
A
Sr
AD,1
A
<byte>
A\
P
Activities that are underlined denote an optional read access to verify the success of the command.
Case B: 1-Wire Busy (1WB = 1)
S
AD,0
A
WCFG
A\
P
The master should stop and restart as soon as the DS2482-100 does not acknowledge the command code.
1-Wire Reset (To Begin or End 1-Wire Communication)
Case A: 1-Wire Idle (1WB = 0), No Busy Polling to Read the Result
S
AD,0
A
1WRS
A
P
(Idle)
S
AD,1
A
<byte>
A\
P
In the first cycle, the master sends the command. Then the master waits (Idle) for the 1-Wire reset to complete. In
the second cycle, the DS2482-100 is accessed to read the result of the 1-Wire reset from the Status Register.
Case B: 1-Wire Idle (1WB = 0), Busy Polling Until the 1-Wire Command is Completed, then Read the Result
S
AD,0
A
1WRS
A
Sr
AD,1
A
<byte>
A
<byte>
A\
P
REPEAT UNTIL THE 1WB BIT HAS CHANGED TO 0.
Case C: 1-Wire Busy (1WB = 1)
S
AD,0
A
1WRS
A\
P
The master should stop and restart as soon as the DS2482-100 does not acknowledge the command code.
18
______________________________________________________________________________________
Single-Channel 1-Wire Master
1-Wire Single Bit (To Generate a Single Time Slot on the 1-Wire Line)
Case A: 1-Wire Idle (1WB = 0), No Busy Polling
S
AD,0
A
1WSB
A
<byte>
A
P
(Idle)
S
AD,1
A
<byte>
A\
P
The idle time is needed for the 1-Wire function to complete. Then access the device in read mode to get the
result from the 1-Wire Single Bit command.
Case B: 1-Wire Idle (1WB = 0), Busy Polling Until the 1-Wire Command is Completed
S
AD,0
A
1WSB
A
<byte>
A
Sr
REPEAT UNTIL THE 1WB BIT
HAS CHANGED TO 0.
AD,1
A
<byte>
A
<byte>
A\
P
When 1WB has changed from 1 to 0, the Status Register holds the valid result of the 1-Wire Single Bit command.
Case C: 1-Wire Busy (1WB = 1)
S
AD,0
A
1WSB
A\
P
The master should stop and restart as soon as the DS2482-100 does not acknowledge the command code.
1-Wire Write Byte (To Send a Command Code to the 1-Wire Line)
Case A: 1-Wire Idle (1WB = 0), No Busy Polling
S
AD,0
A
1WWB
A
33h
A
P
(Idle)
33h is the valid 1-Wire ROM function command for Read ROM. The idle time is needed for the 1-Wire function to
complete. There is no data read back from the 1-Wire line with this command.
Case B: 1-Wire Idle (1WB = 0), Busy Polling Until the 1-Wire Command is Completed.
S
AD,0
A
1WWB
A
33h
A
Sr
REPEAT UNTIL THE 1WB BIT
HAS CHANGED TO 0.
AD,1
A
<byte>
A
<byte>
A\
P
When 1WB has changed from 1 to 0, the 1-Wire Write Byte command is completed.
Case C: 1-Wire Busy (1WB = 1)
S
AD,0
A
1WWB
A\
P
The master should stop and restart as soon as the DS2482-100 does not acknowledge the command code.
______________________________________________________________________________________
19
DS2482-100
I2C Communication Examples (continued)
DS2482-100
Single-Channel 1-Wire Master
I2C Communication Examples (continued)
1-Wire Read Byte (To Read a Byte from the 1-Wire Line)
Case A: 1-Wire Idle (1WB = 0), No Busy Polling, Set Read Pointer After Idle Time
S
AD,0
A
1WRB
A
P
(Idle)
S
AD,0
A
SRP
A
E1h
A
Sr
AD,1
A
<byte>
A\
P
The idle time is needed for the 1-Wire function to complete. Then set the read pointer to the Read Data Register
(code E1h) and access the device again to read the data byte that was obtained from the 1-Wire line.
Case B: 1-Wire Idle (1WB = 0), No Busy Polling, Set Read Pointer Before Idle Time
S
AD,0
A
1WRB
A
Sr
AD,0
A
SRP
A
E1h
A
(Idle)
S
AD,1
A
<byte>
A\
P
P
The read pointer is set to the Read Data Register (code E1h) while the 1-Wire Read Byte command is still in
progress. Then, after the 1-Wire function is completed, the device is accessed to read the data byte that was
obtained from the 1-Wire line.
Case C: 1-Wire Idle (1WB = 0), Busy Polling Until the 1-Wire Command is Completed
S
AD,0
A
Sr
1WRB
AD,0
A
A
REPEAT UNTIL THE 1WB BIT
HAS CHANGED TO 0.
Sr
AD,1
A
<byte>
A
<byte>
A\
SRP
A
E1h
A
Sr
AD,1
A
<byte>
A\
P
Poll the Status Register until the 1WB bit has changed from 1 to 0. Then set the read pointer to the Read Data
Register (code E1h) and access the device again to read the data byte that was obtained from the 1-Wire line.
Case D: 1-Wire Busy (1WB = 1)
S
AD,0
A
1WRB
A\
P
The master should stop and restart as soon as the DS2482-100 does not acknowledge the command code.
20
______________________________________________________________________________________
Single-Channel 1-Wire Master
1-Wire Triplet (To Perform a Search ROM Function on the 1-Wire Line)
Case A: 1-Wire Idle (1WB = 0), No Busy Polling
S
AD,0
A
1WT
A
<byte>
A
P
(Idle)
S
AD,1
A
<byte>
A\
P
The idle time is needed for the 1-Wire function to complete. Then access the device in read mode to get the
result from the 1-Wire Triplet command.
Case B: 1-Wire Idle (1WB = 0), Busy Polling Until the 1-Wire Command is Completed
S
AD,0
A
1WT
A
<byte>
A
Sr
REPEAT UNTIL THE 1WB BIT
HAS CHANGED TO 0.
AD,1
A
<byte>
A
<byte>
A\
P
When 1WB has changed from 1 to 0, the Status Register holds the valid result of the 1-Wire Triplet command.
Case C: 1-Wire Busy (1WB = 1)
S
AD,0
A
1WT
A\
P
The master should stop and restart as soon as the DS2482-100 does not acknowledge the command code.
Applications Information
SDA and SCL Pullup Resistors
SDA is an open-drain output on the DS2482-100 that
requires a pullup resistor to realize high-logic levels.
Because the DS2482-100 uses SCL only as input (no
clock stretching), the master can drive SCL either
through an open-drain/-collector output with a pullup
resistor or a push-pull output.
Pullup Resistor RP Sizing
According to the I2C specification, a slave device must
be able to sink at least 3mA at a VOL of 0.4V. This DC
condition determines the minimum value of the pullup
resistor as:
RP(MIN) = (VCC - 0.4V)/3mA
With an operating voltage of 5.5V, the minimum value
for the pullup resistor is 1.7kΩ. The “MINIMUM RP” line
in Figure 11 shows how the minimum pullup resistor
changes with the operating voltage.
For I2C systems, the rise time and fall time are measured from 30% to 70% of the pullup voltage. The maximum bus capacitance, CB, is 400pF. The maximum rise
time must not exceed 1000ns at standard speed and
300ns at fast speed. Assuming maximum rise time, the
maximum resistor value at any given capacitance CB is
calculated as:
RPMAXS = 1000ns/[CB x ln(7/3)] (standard speed)
RPMAXF = 300ns/[CB x ln(7/3)] (fast speed)
For a bus capacitance of 400pF, the maximum pullup
resistor values are 2.95kΩ at standard speed and 885Ω
at fast speed. A value between 1.7kΩ and 2.95kΩ
meets all requirements at standard speed.
Because an 885Ω pullup resistor, as would be required
to meet the rise time specification at fast speed and
400pF bus capacitance, is lower than RP(MIN) at 5.5V, a
different approach is necessary. The “MAX LOAD AT
MIN RP FAST MODE” line in Figure 11 is generated by
first calculating the minimum pullup resistor at any
given operating voltage (“MINIMUM RP” line) and then
calculating the respective bus capacitance that yields a
300ns rise time.
Only for pullup voltages of 3V and lower can the maximum
permissible bus capacitance of 400pF be maintained. A
______________________________________________________________________________________
21
DS2482-100
I2C Communication Examples (continued)
reduced bus capacitance of 300pF is acceptable for
pullup voltages of 4V and lower. For fast speed operation
at any pullup voltage, the bus capacitance must not
exceed 200pF. The corresponding pullup resistor value
at the voltage is indicated by the “MINIMUM RP” line.
VCC
CURRENT-LIMITING
RESISTOR
REFER TO APPLICATION
NOTE 4206
RP*
SDA
SCL
(I2C PORT)
μC
PCTLZ
DS2482-100
AD0
AD1
1-Wire LINE
IO
1-Wire DEVICE #1
(WITH SPECIAL POWER
REQUIREMENTS)
VCC
SDA
SCL
PCTLZ
DS2482-100
VCC
AD0
AD1
1-Wire LINE
IO
1-Wire
DEVICE #2
*RP = I2C PULLUP RESISTOR (SEE THE APPLICATIONS INFORMATION SECTION FOR RP SIZING).
2000
500
1600
400
1200
300
MINIMUM RP
800
200
MAX LOAD AT MIN RP FAST MODE
400
100
0
0
1
2
3
4
5
PULLUP VOLTAGE (V)
Figure 11. I2C Fast Mode Pullup Resistor Selection Chart
22
______________________________________________________________________________________
LOAD (pF)
Figure 10. Application Schematic
MINIMUM RP (Ω)
DS2482-100
Single-Channel 1-Wire Master
Single-Channel 1-Wire Master
TOP VIEW
(BUMP SIDE DOWN)
TOP MARK
DS2482-100
1
TOP VIEW
2
DS2482-100
3
1
+
+
A
VCC
1
8 AD0
IO
2
7 AD1
AD1
AD0
2 4 8 2 1
B
DS2482-100
3
6 PCTLZ
SCL
4
5 SDA
3
A
PCTLZ
GND
2
+
B
SCL
SDA
VCC
# # # x x
C
C
GND
SO (150 mils)
y y w w r r
IO
WLP
WLP
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains
to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
LAND PATTERN NO.
8 SO (150 mils)
S8+4
21-0041
90-0096
9 WLP
W92A1+1
21-0067
Refer to
Application Note 1891
______________________________________________________________________________________
23
DS2482-100
Pin Configurations
DS2482-100
Single-Channel 1-Wire Master
Revision History
REVISION
NUMBER
REVISION
DATE
1
080604
2
110204
DESCRIPTION
Initial release
—
I2C trademark note deleted; upper I2C slave address bits changed from 01100b to
00110b.
3
040507
Added the lead(Pb)-free ordering information.
4
091007
Added the UCSP (WLP) package and Package Information section.
5
6
061208
7/08
7
8/08
8
11/09
9
1/12
PAGES
CHANGED
1, 14
1
1, 21
Updated the Features bullets.
1
Updated the VIL1 and RWPU values in the Electrical Characteristics table.
2
Minor corrections to Figure 1; updated the Detailed Description section to clarify
information about the active pullup and strong pullup.
5
Replaced the Strong Pullup (SPU) section description and replaced Figure 4.
7
Removed timing inaccuracies in Figure 8.
14
Created newer template-style data sheet.
All
Replaced Figure 8.
16
Deleted the 1-Wire line termination resistor and references to it in the Typical
Operating Circuit and in Figure 11.
Corrected the recommendation for using active pullup (APU); removed the
references to presence-pulse masking.
Updated the soldering information in the Absolute Maximum Ratings section;
added a note to the Strong Pullup (SPU) section description; updated the 1-Wire
Reset command description (sections Restriction and Configuration Bits
Affected); added the land pattern to the Package Information section.
1, 23
1–7, 9–12, 15,
16, 21, 22, 24
2, 7, 10, 23
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
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