User Manual

System overview
Data maintenance
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● Desigo CC: AMEV profile MOU-B
● Desigo PX: AMEV profile AS-B
Desigo room automation
BACnet is used to exchange information between PX automation stations and DXR2 and PXC3 room
automations stations and the management platform.
Desigo RX
The Desigo RXB room automation range communicates via KNX S-Mode (EIB).
Restrictions for LonWorks
A LonWorks network cannot be segmented with LonWorks routers, as the message length for BACnet is
228 bytes for performance reasons. Commercially available LonWorks routers do not have sufficiently large
buffers for this length. No other media (power lines, infrared, etc.) can be used either.
For performance reasons, we do not recommend the operation of LonWorks and BACnet devices on the
same LonTalk cable.
3.9 Data maintenance
A running Desigo system contains various categories of data, each with different requirements in terms of
consistency, period of useful life and visibility. The data is distributed throughout the system, with each
category having a unique origin. There is no central data maintenance in the Desigo system. The system
data is distributed on all devices throughout the network, but is primarily located in the automation
stations.
During the sales, planning, engineering and commissioning phases, project data is created. Part of the data
is loaded into the system, while another part is tool-specific and used, e.g., for documentation of the
project.
System data is:
● Process-data and parameter settings
● Archived data
● Configuration and description data
● Metadata
● D-MAP program
● Graphics and masks
● Libraries
● Offline trend object values
Process-data and parameter settings
Process data
Process data is data generated by the physical process in the building using a process control algorithm.
Process data represents the process variables, such as a temperature or a damper position.
Parameter settings
Parameter settings are function parameters, settings, setpoints, etc. which are defined for each plant or
project and which affect the way in which an application works. Parameter settings can be modified during
operation.
Process data and parameter settings can be accessed within the system via BACnet objects, e.g., Present
Value [PrVal] and Status [StaFlg], if the associated mapping is enabled in the engineering phase.
If process data is used by several automation stations, the data origin is the location where the physical
variable is measured (e.g., outdoor temperature) or generated (e.g., the control signal from a time
schedule). Copies are updated on an event-driven basis after a short delay.
Displaying process data and parameter settings
To display process data and parameter settings mapped to BACnet on clients, only one copy of the data
needed for current operation and monitoring is stored. The Desigo system does not store complete copies
of process data or parameter settings. The data (copy) required by a client is normally updated via the
BACnet protocol on an event-driven basis and with a short time delay.