Westermo MA-67 - Manual (Page 7)

13 6067-2001
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The MA-67 like other Westermo products MA-42, MD-42, MD-63, LD-64, MA-44,
MD-44, MM-42, MA-49, MA-47, RA-48, RD-48 and LD-63 uses the RS-422/485
interfaces.
RS-422/485 were designed for multidrop applications. When a system is installed it
should form a bus structure. Star shaped networks should never be created, there are
other Westermo products designed to work in star net applications. To correctly install,
an RS-422/485 network should be terminated at the correct points.
The recommendation is to terminate the receiver on the first unit and the final bus unit.
See diagrams under the headline ”Line connection” for details of how this is done with
RS-485 (2 wire) and RS-422 (4 wire).
If any problems do occur on set up of the MA-67, the LEDs will be helpful.
- PWR: The unit has power.
- RD: Data received on the opto interface.
- TD: Data received on the RS-422/485 interface.