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DS2409P-TU0026R

MicroLAN Coupler

Maxim Integrated 

DS2409

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

1

TX

Reset

Reset pulse (480–960 µs)

2

RX

Presence

Presence pulse

3

TX

ECh

Issue “conditional search ROM” command

4

RX/RX/TX

for each of the 64 ROM bits Identify and access one of the qualifying devices

5

TX

33h

Issue Smart-On Auxiliary command

6

TX

FFh

Send reset stimulus

7

RX

<data byte>*

Get reset response byte with presence info

8

RX

33h

Get confirmation byte

9

TX

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.

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