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DS2409

MicroLAN Coupler

Dallas Semiconductor -> Maxim Integrated 

DS2409

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

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