DS2409P/T&R - Dallas Semiconductor

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FEATURES

§ Low impedance coupler to create large

common-ground, multi-level MicroLAN

networks

§ Keeps inactive branches pulled high to 5V

§ Simplifies network topology analysis by

logically decoupling devices on active

network segments

§ Conditional search for fast event signaling

§ Auxiliary 1-WireTM line to connect a memory

chip or to be used as digital input

§ Programmable, general purpose open drain

control output

§ Communicates at 16.3k bits per second

§ Unique, factory-lasered and tested 64-bit

registration number (8-bit family code + 48-

bit serial number + 8-bit CRC tester) assures

absolute traceability because no two parts are

alike

§ 8-bit family code specifies device

communication requirements to bus master

§ Built-in multidrop controller ensures

compatibility with other MicroLAN products

§ Operating temperature range from -40°C to

+85°C

§ Compact, low cost 6-pin TSOC surface mount

package

PIN ASSIGNMENT

PIN DESCRIPTION

Pin 1 GND

Pin 2 1-Wire in

Pin 3 Main 1-Wire out

Pin 4 Auxiliary 1-Wire out

Pin 5 Control Output

Pin 6 VDD

ORDERING INFORMATION

DS2409P 6-pin TSOC package

DESCRIPTION

The MicroLAN coupler is an essential component to build and control 1-Wire MicroLAN networks with

multi-level branching. In contrast to approaches that switch the ground line, the coupler maintains a

common ground level for the whole network and keeps the inactive segments powered. This simplifies

supplying central or local power for additional circuitry and prevents loss of status of parasitically

powered devices. It also avoids disrupting communication caused by the parasitic power supply of 1-Wire

devices after activating a branch. The coupler does not contain any user-programmable memory. To label

a branch one can connect any 1-Wire memory device to the auxiliary 1-Wire output of the coupler. Both

the main and the auxiliary 1-Wire output are supported by a “smart-on” command. This command

generates a reset/presence sequence on the selected output before the electronic switch closes the contact

to the 1-Wire bus. This way the bus master can apply a ROM function command (optionally followed by

a memory function) to the devices on the just activated segment with all other devices in the network

DS2409

MicroLAN Coupler

www.dalsemi.com

TOP VIEW

3.7 X 4.0 X 1.5 mm

SIDE VIEW

6-PIN TSOC PACKAGE

DS2409

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remaining deselected. This significantly speeds up the analysis of topology and population in a

continuously changing network. The coupler also supports the bus master in detecting arrivals on the

inactive segments of the network by responding to the conditional search command. The control output

can be used to optically signal the on/off state of a branch or, together with the auxiliary output, for

handshaking in dual-master applications. The network size can be maximized by using a DS2480 line

driver at the bus master’s serial interface. The DS2480 compensates for the rising ground level caused by

the non-zero on-resistance of couplers in multi-level networks.

OVERVIEW

The DS2409 Coupler provides a means to create large MicroLAN networks with additional control

capability provided by an open-drain N-channel MOSFET that can be remotely switched via

communication over the 1-Wire bus (Figure 1). An auxiliary output can be used to label the branch by

connecting a programmed 1-Wire memory chip or as digital input. The DS2409 contains a factory-lasered

registration number that includes a unique 48-bit serial number, an 8-bit CRC, and an 8-bit family code

(1FH). The 64-bit ROM portion of the DS2409 not only creates an absolutely unique electronic

identification for the device itself but also is a means to locate and address the device in order to exercise

its control functions.

The DS2409 uses the standard Dallas Semiconductor 1-Wire protocol for data transfers (Figure 2), with

all data being read and written least significant bit first. Communication to and from the DS2409 requires

a single bi-directional line that is typically a port pin of a microcontroller. The 1-Wire bus master

(microcontroller) must first issue one of five ROM function commands: 1)Read ROM, 2) Match ROM,

3) Search ROM, 4) Skip ROM, or 5) Conditional Search ROM. These commands operate on the 64-bit

lasered ROM portion of each device and can singulate a specific device if many are present on the 1-Wire

line as well as indicate to the bus how many and what type of each device is present. After a ROM

function command is successfully executed, the control functions of the device can be exercised via the 1-

Wire bus.

BLOCK DIAGRAM Figure 1

DS2409

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64-BIT LASERED ROM

Each DS2409 contains a unique ROM code that is 64 bits long. The first eight bits are a 1-Wire family

code. The next 48 bits are a unique serial number. The last eight bits are a CRC of the first 56 bits. (See

Figure 3.) The 1-Wire CRC of the lasered ROM is generated using the polynomial X8 + X5 + X4 + 1.

Additional information about the Dallas Semiconductor 1-Wire Cyclic Redundancy Check is available in

the Book of DS19xx iButton Standards. The 64-bit ROM and ROM Function Control section allow the

DS2409 to operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section “1-Wire Bus

System”. The functions required to exercise the control functions of the DS2409 are not accessible until

the ROM function protocol has been satisfied. This protocol is described in the ROM functions flow

chart (Figure 7). The 1-Wire bus master must first provide one of the five ROM function commands.

After a ROM function sequence has been successfully executed, the bus master may then provide any one

of the function commands specific to the DS2409 (Figure 5).

HIERARCHICAL STRUCTURE FOR 1-WIRE PROTOCOL Figure 2

64-BIT LASERED ROM Figure 3

MSB LSB

8-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code (1FH)

MSB LSB MSB LSB MSB LSB

DS2409

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1-WIRE CRC GENERATOR Figure 4

CONTROL FUNCTION COMMANDS

The “Control Function Flow Chart” (Figure 5) describes the protocols necessary for controlling the main

and auxiliary output as well as the control output of the DS2409. The 1-Wire Function Control section

and the Coupler Function Control section combine to interpret the commands issued by the bus master

and create the correct control signals within the device. Depending on the complexity of function to be

exercised, the 1-byte command code may require one or two more bytes being sent by the bus master.

Switching one branch on implies that the other branch is automatically switched off. At power-on, both

branches are switched off. Each command flow includes at least one byte of feedback information for the

bus master to check if the command was understood and executed.

STATUS READ/WRITE [5Ah]

This command should be sent to the device after powering up unless the default settings are adequate for

the application. Following the command code, the bus master has to send the status control byte. The bus

master will then read the status info byte from the device. The confirmation byte is identical to the status

info byte. Tables 1 and 2 show the bit assignments in both bytes.

At power-on the device will be in the auto-control mode and the control output will be assigned to the

main output. The control output can be assigned to the auxiliary output by setting bit 6 of the status

control byte to a 1. For manual operation of the control output one has to select manual mode (bit 5 = 1).

The value of bit 7 of the status control byte will then determine the status of the control output. A 1 for bit

7 will make the transistor conducting, a 0 will turn it off (non-conducting). To change the status of the

device, both bits 3 and 4 of the status control byte have to be 0. Otherwise the settings will remain

unchanged. In any case, the status info byte will reflect the currently valid settings including the changes

that might have been made with the status control byte.

The status info byte allows the bus master to verify the actual status of each output (STAT,

active/inactive, on/off) and the static level at the main and auxiliary output (LEVL, 1 for normal, 0 in case

of a short). If a 1-Wire output is inactive and a low-going edge is encountered during this time, the

DS2409 will set the event flag (EVNT) the status info byte. Each output has its own event flag. The event

flags are cleared with the All Lines Off command. Bit 7 of the status info byte tells if the device is auto-

control mode or manual mode. Depending on the value of this bit, the information in bit 6 (CNTR.

STAT) either reports the association of the control output to a particular output (auto-control mode) or the

status of the transistor at the control output.

DS2409

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STATUS CONTROL BYTE Table 1

76543210

DATA

XCNTR.

SEL. MODE R/WR/WX X X

0-2 X don’t care

3-4 R/WWrite control: both bits must be 0 to change the status.

5MODE control output mode selection: 0 = auto-control mode (default), 1 = manual mode

6CNTR.

SEL. control output association (auto-control mode): 0 = main (default), 1 = auxiliary

7DATA

XValue to be written to control output (manual mode only): don’t care otherwise

STATUS INFO BYTE Table 2

76543210

MODE CNTR.

STAT EVNT

AUX. EVNT

MAIN AUX.

LEVL AUX.

STAT MAIN

LEVL MAIN

STAT

0MAIN

STAT status of main output: 0 = active (connected to bus master), 1 = inactive

1MAIN

LEVL voltage sensed at main output: 0 = low, 1 = high (see note)

2AUX.

STAT status of auxiliary output: 0 = active (connected to bus master), 1 = inactive

3AUX.

LEVL voltage sensed at auxiliary output: 0 = low, 1 = high (see note)

4EVNT

MAIN event flag for main output: 0 = no event, 1 = negative edge sensed since inactive

5EVNT

AUX. event flag for aux. Output: 0 = no event, 1 = negative edge sensed since inactive

6CNTR.

STAT if auto-control mode: control output association, 0 = main, 1 = auxiliary

if manual mode: 0 = output transistor off, 1 = output transistor on

7MODE control output mode: 0 = auto-control mode, 1 = manual mode

Note: Data is valid only if the output is decoupled from the 1-Wire input.

ALL LINES OFF [66h]

This command is used to deactivate the currently active 1-Wire output and to clear both event flags or to

end a discharge cycle initiated by the Discharge Lines command. Before issuing this command, one

should read the status and check the event flags of both, the main and the auxiliary output. Otherwise one

might inadvertently clear the event flag without having taken appropriate action. If the DS2409 is in auto-

control mode, the transistor at the control output will be switched off (non-conducting). At power-on, the

device will automatically perform the All Lines Off command. In contrast to a power-on cycle, the All

Lines Off command does not clear the Mode and Control Select bits.

DS2409

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DISCHARGE LINES [99h]

There may be situations where one has to force a power-on reset for parasitically powered 1-Wire devices

connected to the main or auxiliary output of the DS2409. For this purpose the Discharge Lines command

has been implemented. This command first deactivates the output lines and then turns on the pulldown

transistors of both, the main and the auxiliary outputs. This state will be maintained until the bus master

accesses the coupler again and issues a different control function command. The duration of the

discharge time should be 100 ms minimum and is controlled solely by the bus master.

Although any of the other control function commands will end the discharge cycle, it is recommended to

use the All Lines Off or Status Read/Write command to do so. This will allow the discharged lines to

fully recharge and prevent a sudden voltage droop on the active part of the network in case of a Direct-On

Main command. This precaution is not necessary with the Smart-On command.

DIRECT-ON MAIN [A5h]

The Direct-on Main command is typically used to activate the main 1-Wire output to subsequently issue a

reset pulse and access a device residing on the segment of the MicroLAN connected to the Main output of

the DS2409. If this command is received, the DS2409 will automatically set the auxiliary output to

inactive. Depending on the currently valid device status settings, the transistor at the control output may

change state (see Status Read/Write command).

SMART-ON MAIN [CCh]

When analyzing huge MicroLAN networks for changes in population it may be useful to limit the number

of devices participating in a Search ROM command. The smaller the number of participants, the faster

the responding devices are identified. The DS2409 supports the bus master in this process with the Smart-

On Main command. As a preparation for the subsequent steps, the first action of the Smart-On Main

command is deactivating the main output.

Compared to the Direct-On Main command, the Smart-On Main requires the bus master to follow the

function command with 16 more time slots. The first 8 time slots (reset stimulus) are translated by the

DS2409 as a reset low time on the Main 1-Wire output. Now the bus master reads the reset response byte.

This generates the reset high time where devices connected to the Main 1-Wire output may assert their

presence pulse. If a presence pulse was found, several of the most significant bits of the reset response

byte will be zeros. After these 16 time slots are completed the Main 1-Wire output will be activated (=

through-connected to the 1-Wire input of the DS2409). Now only the devices on the newly activated

segment of the MicroLAN are ready to receive a ROM function command optionally followed by a

memory function command. All other devices in the network will remain silent until the next reset pulse

is issued.

As with the Direct-On command, the Smart-On Main command will automatically set the auxiliary

output to inactive. Depending on the currently valid device status settings, the transistor at the control

output may change state (see Status Read/Write command). If the Smart-On Main command is terminated

by a 1-Wire reset pulse while receiving the reset stimulus, the DS2409 will immediately turn off the

pulldown transistor and let the output line go high.

SMART-ON AUXILIARY [33h]

This command works essentially the same way as the Smart-On Main command, but it affects the

auxiliary 1-Wire output. After the reset response byte is received by the bus master, the auxiliary output is

activated and the main output becomes inactive. Depending on the currently valid device status settings,

the transistor at the control output may change state (see Status Read/Write command).

DS2409

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FUNCTION COMMAND FLOW CHART Figure 5

DS2409

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FUNCTION COMMAND FLOW CHART Figure 5 cont’d

DS2409

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HARDWARE CONFIGURATION Figure 6

1-WIRE BUS SYSTEM

The 1-Wire bus is a system which has a single bus master and one or more slaves. In all instances the

DS2409 behaves as a slave. The discussion of this bus system is broken down into three topics: hardware

configuration, transaction sequence, and 1-Wire signaling (signal types and timing). A 1-Wire protocol

defines bus transactions in terms of the bus state during specified time slots that are initiated on the

falling edge of sync pulses from the bus master. For a more detailed protocol description, refer to Chapter

4 of the Book of DS19xx iButton Standards.

Hardware Configuration

The 1-Wire bus has only a single line by definition; it is important that each device on the bus be able to

drive it at the appropriate time. To facilitate this, each device attached to the 1-Wire bus must have open

drain or 3-state outputs. The 1-Wire input of the DS2409 is open drain with an internal circuit equivalent

to that shown in Figure 6. A multidrop bus consists of a 1-Wire bus with multiple slaves attached. The 1-

Wire bus has a maximum data rate of 16.3k bits per second and requires a pullup resistor of

approximately 1.5k? or a DS2480 driver for MicroLAN applications.

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. If this does not occur and the bus is left low

for more than 120 µs, one or more of the devices on the bus may be reset. The DS2409 may perform a

power-on reset cycle and deactivate both 1-Wire outputs if the 1-Wire input is low for minimum 8 ms. A

low time of 12 ms or more will always cause a power-on reset cycle.

Transaction Sequence

The protocol for accessing the DS2409 via the 1-Wire port is as follows:

• Initialization

• ROM Function Command

• Control Function Command

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 the DS2409 is on the bus and is ready to

operate. For more details, see the “1-Wire Signaling” section.

DS2409

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ROM FUNCTION COMMANDS

Once the bus master has detected a presence, it can issue one of the five ROM function commands. All

ROM function commands are eight bits long. A list of these commands follows (refer to flowchart in

Figure 7):

Read ROM [33h]

This command allows the bus master to read the DS2409s 8-bit family code, unique 48-bit serial number,

and 8-bit CRC. This command can only be used if there is a single DS2409 on the bus. If more than one

slave is present on the bus, a data collision will occur when all slaves try to transmit at the same time

(open drain will produce a wired-AND result). The resultant family code and 48-bit serial number will

usually result in a mismatch of the CRC.

Match ROM [55h]

The match ROM command, followed by a 64-bit ROM sequence, allows the bus master to address a

specific DS2409 on a multidrop bus. Only the DS2409 that exactly matches the 64-bit ROM sequence

will respond to the following memory function command. All slaves that do not match the 64-bit ROM

sequence will wait for a reset pulse. This command can be used with a single or multiple devices on the

bus.

Skip ROM [CCh]

This command can save time in a single drop bus system by allowing the bus master to access the control

functions without providing the 64-bit ROM code. If more than one slave is present on the bus and a read

command is issued following the Skip ROM command, data collision will occur on the bus as multiple

slaves transmit simultaneously (open drain pulldowns will produce a wired-AND result).

Search ROM [F0h]

When a system is initially brought up, the bus master might not know the number of devices on the 1-

Wire bus or their 64-bit ROM codes. The search ROM command allows the bus master to use a process

of elimination to identify the 64-bit ROM codes of all slave devices on the bus. The search ROM process

is the repetition of a simple 3-step routine: read a bit, read the complement of the bit, then write the

desired value of that bit. The bus master performs this simple, 3-step routine on each bit of the ROM.

After one complete pass, the bus master knows the contents of the ROM in one device. The remaining

number of devices and their ROM codes may be identified by additional passes. See Chapter 5 of the

Book of DS19xx iButton Standards for a comprehensive discussion of a search ROM, including an actual

example.

Conditional Search ROM [ECh]

This ROM command works exactly as the normal ROM Search, but it will identify only devices that

encounter certain conditions. The DS2409 will respond to this command only if the event flag for the

main output is set (see Status Read/Write command). The event flag is cleared with the All Lines Off

command.

DS2409

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ROM FUNCTIONS FLOW CHART Figure 7

DS2409

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1-WIRE SIGNALING

The DS2409 requires strict protocols to ensure data integrity. The protocol consists of four types of

signaling on one line: Reset Sequence with Reset Pulse and Presence Pulse, Write 0, Write 1 and Read

Data. All these signals except presence pulse are initiated by the bus master. The initialization sequence

required to begin any communication with the DS2409 is shown in Figure 8. A reset pulse followed by a

presence pulse indicates the DS2409 is ready to send or receive data given the correct ROM command

and control function command. The bus master transmits (TX) a reset pulse (tRSTL, minimum 480 µs).

The bus master then releases the line and goes into receive mode (RX). The 1-Wire bus is pulled to a high

state via the pullup resistor. After detecting the rising edge on the data line, the DS2409 waits (tPDH, 15-60

µs) and then transmits the presence pulse (tPDL, 60-240 µs).

INITIALIZATION PROCEDURE “RESET AND PRESENCE PULSES” Figure 8

*In order not to mask interrupt signaling by other devices on the 1-Wire bus, tRSTL + tR should always be

less than 960 µs.

**The slew rate of the Presence Pulse is actively limited by the DS2409 to 1V/µs typically to minimize

ringing. The slope of all other edges is controlled by the 1-Wire bus driver at the host.

READ/WRITE TIME SLOTS

The definitions of write and read time slots are illustrated in Figure 9. All time slots are initiated by the

master driving the data line low. The falling edge of the data line synchronizes the DS2409 to the master

by triggering a delay circuit in the DS2409. During write time slots, the delay circuit determines when the

DS2409 will sample the data line. For a read data time slot, if a “0” is to be transmitted, the delay circuit

determines how long the DS2409 will hold the data line low overriding the 1 generated by the master. If

the data bit is a “1”, the device will leave the read data time slot unchanged.

DS2409

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READ/WRITE TIMING DIAGRAM Figure 9

DS2409

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USAGE EXAMPLE

Configuration: A bus master controls a MicroLAN consisting of a trunk with many DS2409s that create

branches. Each of the DS2409s has a DS2430A connected to its auxiliary output to label its physical

location in the network (see Figure 10). iButton devices are constantly arriving at or departing from the

branches.

Task: Identify one branch where an iButton has arrived and get the branch’s physical location. Determine

the population on that particular branch.

STEP MASTER MODE DATA (LSB FIRST) COMMENTS

1TX Reset Reset pulse (480–960 µs)

2RX Presence Presence pulse

3TX ECh Issue “conditional search ROM” command

4RX/RX/TX for each of the 64 ROM bits Identify and access one of the qualifying devices

5TX 33h Issue Smart-On Auxiliary command

6TX FFh Send reset stimulus

7RX <data byte>* Get reset response byte with presence info

8RX 33h Get confirmation byte

9TX CCh Issue “skip ROM” command

10 TX F0h Issue “read memory” command

11 RX <32 data bytes> Get branch location information (DS2430A)

12 TX Reset Reset pulse

13 RX Presence Presence pulse

14 TX 55h Issue “Match ROM” command

15 TX <8 byte ROM ID> Access the previously identified coupler

16 TX CCh Issue Smart-On Main command

17 TX FFh Send reset stimulus

18 RX <data byte>* Get reset response byte with presence info

19 RX CCh Get confirmation byte

20 TX F0h Issue “search ROM” command

21 RX/RX/TX for each of the 64 ROM bits Identify one of the devices connected

22 TX Reset Reset pulse

23 RX Presence Presence pulse

24 TX 55h Issue “Match ROM” command

25 TX <8 byte ROM ID> Access the previously identified coupler

26 TX 66h Send all lines off command

27 RX 66h Get confirmation byte

28 TX Reset Reset pulse

29 RX Presence Presence pulse

repeat steps 12 to 21 for each of the remaining devices on the branch of the identified coupler

* 00h or 01h if presence pulse, FFh if no presence pulse

Note: The sequence of steps 12 to 21 logically decouples all other devices residing on the trunk from

responding to the search ROM command. The All Lines Off command is required to clear the event flag

that made the device respond to the conditional search command.

DS2409

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APPLICATION EXAMPLES

Figures 10 and 11 show two application examples of the DS2409 MicroLAN Coupler. A single trunk

with branches is the typical topology of an access control system with the iButtons being the electronic

keys required for admittance. The host computer runs a program that scans the devices on the trunk for

events (conditional search). When somebody touches the probe with an iButton, this will set the event

flag of the main line and the coupler will respond. The ID chip represents the DS2430A that labels the

access point. The 64-bit ROM ID of the arriving iButton is the key for the entrance. In a real access

control application, the LED will be replaced by a solenoid that opens the lock under software control

(manual mode). The same network topology could be used for an inventory control system with the

branches representing individual shelves of a rack. The iButtons would be electronic tags mounted on

objects sitting on the shelves. The LED would guide the warehouse worker in placing the objects onto the

right shelf.

The dual-master system realizes a master to master communication path via the 1-Wire bus. The DS1996

Memory iButton serves as a temporary storage for the data packets to be exchanged. When idle, both

main outputs as well as the auxiliary outputs are inactive. To access the Memory iButton, the host A first

switches on the control output, thereby pulling the auxiliary line of the coupler at the B side low. This

tells host B that it is not allowed to activate the main output of coupler B. Now host A activates the main

output of coupler A and writes data to the Memory iButton. After the writing is complete, host A

deactivates the main output of coupler A and switches off the control output. Host B meanwhile has been

polling the logic level at the auxiliary line of coupler B and realizes that host A has finished the access.

Now host B follows the same procedure and accesses the memory to read the data, etc. The memory

iButton may be replaced by a MicroLAN network. The Silicon Label stores information telling the hosts

that these particular couplers access the same network and that the control and auxiliary outputs are cross-

coupled for handshaking.

MicroLAN TRUNK WITH BRANCHES Figure 10

DS2409

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DUAL MASTER SYSTEM Figure 11

DS2409

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ABSOLUTE MAXIMUM RATINGS*

Voltage on Data to Ground -0.5V to +7.0V

Operating Temperature -40°C to +85°C

Storage Temperature -55°C to +125°C

Soldering Temperature 260°C for 10 seconds

* This is a stress rating only and functional operation of the device at these or any other conditions above

those indicated in the operation sections of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods of time may affect reliability.

DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C, VDD = 5V ±10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Logic 1 (1-Wire In) VIH1 2.2 VDD V 1

Logic 0 (1-Wire In) VIL1 -0.3 +0.8 V 1

Output Logic Low @ 4 mA (1-Wire In) VOL1 0.4 V 1

Output Logic High (1-Wire In) VOH1 VPUP V 1, 3

Input Load Current (1-Wire In) IL1 5 µA 4

Logic 1 (Main Out) VIHM 2.2 V 1

Logic 0 (Main Out) VILM -0.3 +0.8 V 1

Output Sink Current @ 0.4V (Main Out) ISM 10 mA 1, 8

Logic 1 (Aux. Out) VIHA 2.2 V 1

Logic 0 (Aux. Out) VILA -0.3 +0.8 V 1

Output Sink Current @ 0.4V (Aux. Out) ISA 10 mA 1

Output Leakage (Control Output) ILOC 1 µA

Current @ 0.4V (Control Output) IOLC 10 mA

Operating Current IDD 50 µA 2

Quiescent Current IDDQ 25 µA 2

CAPACITANCE (tA = 25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Capacitance 1-Wire In CIN1 50 pF

Capacitance Main Out CINM 50 pF

Capacitance Aux. Out CINA 50 pF

RESISTANCES (-40°C to +85°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

1-Wire In to Main ON Res. ZMON 10 20 ?

1-Wire In to Aux. ON Res. ZAON 15 30 ?

Main and Aux. Pullup Res. RPU 1.5 k?

DS2409

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AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C, VDD = 5V ±10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Time Slot tSLOT 60 120 µs

Write 1 Low Time tLOW1 1 15 µs

Write 0 Low Time tLOW0 60 120 µs

Read Low Time tLOWR 1 15 µs

Read Data Valid tRDV exactly 15 µs

Release Time tRELEASE 0 15 45 µs

Read Data Setup tSU 1 µs 6

Recovery Time tREC 1 µs

Reset Time High tRSTH 480 µs 5

Reset Time Low tRSTL 480 960 µs 7

Presence Detect High tPDH 15 60 µs

Presence Detect Low tPDL 60 240 µs

NOTES:

1. All voltages are referenced to ground.

2. Measured with outputs open.

3. VPUP = external pullup voltage.

4. Input load is to ground.

5. An additional reset or communication sequence cannot begin until the reset high time has expired.

6. Read data setup time refers to the time the bus master must pull the I/O line low to read a bit. Data is

guaranteed to be valid within 1 µs of this falling edge.

7. The reset low time (tRSTL) should be restricted to a maximum of 960 µs, to allow interrupt signaling,

otherwise, it could mask or conceal interrupt pulses. The DS2409 may perform a power-on reset cycle

and deactivate both 1-Wire outputs if the 1-Wire input is low for minimum 8 ms. A low time of 12 ms

or more will always cause a power-on reset cycle.

8. The main output has a slew rate controlled output. The indicated current is a DC value. The sink

current typically reaches 80% of its DC value 1 µs after turning on the transistor.