Datalogic DS8100A, Reference Manual

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DS8100A REFERENCE MANUAL
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3.2.3 RS485 Half-Duplex Interface
NOTE
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.
CBX100/500 Function
RTX+ RS485 Receive/Transmit Data +
RTX- RS485 Receive/Transmit Data -
SGND Signal Ground
SGND RTX485-
USER INTERFACE
SGND RTX+
RTX-
SCANNER
Figure 20 - 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 21 shows a multidrop configuration with DS8100A scanners connected to a
Multiplexer.
CAUTION
This is an example of multidrop wiring. Consult the multiplexer manual for
complete wiring instructions.