3.2.3 RS485 Half-Duplex Interface
This interface is provided for backward compatibility. We recommend using
the more efficient Lonworks network for Master/Slave or Multiplexer layouts.
The RS485 half-duplex (3 wires + shield) interface is used for polled communication
protocols.
It can be used for Multidrop connections with a Datalogic Multiplexer, (see par. "Multiplexer"
in Appendix A) exploiting a proprietary protocol based on polled mode called MUX32
protocol, where a master device polls slave devices to collect data. The overall maximum
cable length should not exceed 1200 m (3940 ft).
If the shield is tied to ground at the Host, then leave it floating at the CBX. If it is floating at
the Host then tie it to Shield at the CBX.
RS485 Receive/Transmit Data +
RS485 Receive/Transmit Data -
Figure 29 - RS485 Half-duplex Connections
This interface is forced by software when the protocol selected is MUX32 protocol.
In a Multiplexer layout, the Multidrop address must also be set via serial channel by the
Genius™ utility or by the Host Programming Mode.
Figure 30 shows a multidrop configuration with DS6400 scanners connected to a Multiplexer.
This is an example of multidrop wiring. Consult the multiplexer manual for
complete wiring instructions.
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