RS-485 Data Highway, Connections and MFU Setup
Publication PUB091-003-00_0119
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In the ROMpak, there are moveable links, LK1 & LK2, next to SK23. These should connect pins 1 and
2 for termination, or remain at pins 2 and 3 for no termination:
SK 23
SK18
1
1
LK1
LK2
VDR4 VDR5
CH 1
CH 2
Fig 15: Termination for RS-485 highway in ROMpak actuators. The links are shown in
the non-terminated position.
4.5 Inter-connecting the Highway and Setting up the MFU
The three MFU variations (Single, Dual and single repeater) allow for various different highway
connections. The ‘single channel version’ can be used for simple highways, and where there is an
analogue transmitter connected it will also return the value from the transmitter signal. The ‘dual
channel version’ is used for redundant highway applications where the highway integrity is important
and the ‘single highway with repeater version’ can be used for either ring topology connections or
applications where distances are extended.
In those cases where the single highway with repeater is applied in a ring connection, the
communications can travel either way around the ring. In this mode the number of devices that can be
interconnected will depend on the speed of operation of the highway as each unit introduces a small
propagation delay.
Note:
When using the single highway with internal repeater the termination should always be
fitted on both sides of the repeater since there are no other devices on the highway
