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18 - External units
18 External units
18�1 Introduction
An external unit is a unit that is able to communicate with
a WMPro. The WMPro is always the master in a master/
slave setup. A WMPro can communicate with an external
unit in one of three ways: GFBI, WMShare and AeACom.
18�1�1 GFBI
A WMPro can use this interface to communicate with units
connected to the RS485 port. A script language denition
tells the WMPro how to interact with the unit. Type deni-
tions must be based on a master/slave protocol, with the
WMPro taking the role of master and exercising unidirec-
tional control. The response times must also be known in
advance.
Protocols meeting all these requirements include Mod-
bus and a number of proprietary protocols like GENIbus
(Grundfoss), FCbus (Danfoss), etc. You can use GFBI to connect expansion modules for more I/O op-
tions, frequency converters, pump control systems and other PLCs.
There are other protocols that do not use RS485 even though they meet the above requirements. M-
Bus (Meter Bus) falls into this category. If you use a level converter to change RS485 signal to M-Bus
levels, you can use GFBI to connect devices such as electricity, water and other meters to a WMPro.
To use a WMPro in a system running LonWorks or Probus, or another protocol that is not supported
in GFBI, there is a workaround involving Anybus modules from HMS.
External units are units of various kinds that a WMPro is able to share information with as the
master. Examples include expansion units to increase the number of available inputs and out-
puts, a PLC or other subsystem, meters, etc. The WMPro uses RS485 to communicate with exter-
nal units.
An external unit could also be another WMPro, supplying measurements over the network. This
section explains how to connect dierent types of external unit and how to change the settings.
External units
Support for external units was
introduced with rmware release
2.0. Older devices must be upgrad-
ed before the functionality de-
scribed in this section is available.
GFBI
GFBI is short for General Field Bus
Interface. It is a script language
used to describe how to commu-
nicate with many dierent types of
units with dierent protocols.
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