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L-Gate User’s Manual
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For certain applications however, it is necessary that the L-Gate acts as a BACnet client. This
functionality can be configured by activating a “client mapping”. Client mappings can be of
the type “Poll”, “COV”, “Write”, or “Auto”. This specifies how the BACnet client accesses
other BACnet objects on the BACnet network. The “Auto” method determines the best way
(poll, COV, or write) to talk with other server objects. Poll is used for objects that need to
read data from other BACnet objects in a periodic manner. COV is used to subscribe for COV
at other BACnet objects in order to get updates in an event-driven fashion. Write is used to
send updates to other BACnet objects.
When generating matching counter parts to NVs, there are two types of NVs to be considered:
Simple NVs that hold only one value (scalar or enumeration), and structured NVs, that consist
of a number of fields. For simple NVs only one BACnet object per NV is generated. For
structured NVs, one BACnet object is generated for each structure member.
Which type of BACnet object is created depends on the type of the simple NV or of the
structure member. For scalar types analog objects are created. The scaling factors are applied
to the NV to get the resulting scalar value for the Present_Value property. Other properties of
analog objects are derived from the SNVT, including the engineering units, min and max
present value. Multi-state objects are created for NV enumeration types. The EIA-709 state
IDs are sorted and renumbered to start at ‘1’ in BACnet, i.e., a ‘-1’ of MOTOR_NUL in EIA709 maps to a ‘1’ of MOTOR_NUL in BACnet. Optionally, binary objects are created for
enumerated NVs with three states, excluding the ‘-1’ state.
6.1.2 Connections
A connection in the L-Gate specifies which data points exchange values with each other. The
L-Gate supports both “1:n” and “m:1” connections. The single data point is referred to as the
“hub” data point, whereas the other data points are the “target” data points. Only data points
of the same technology can be configured on a single side of the connection.
This means, the following connections are possible:
♦ 1 EIA-709 point maps to n BACnet points,
♦ m EIA-709 points map to one BACnet point,
♦ 1 BACnet point maps to n EIA-709 points,
♦ m BACnet points map to 1 EIA-709 point.
The most common connection will be the 1:1 connection. This is the type of connection that
will be auto-generated by the L-Gate configuration software.
Version 1.0T
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