User Manual

System overview
Data maintenance
3
CM110664en_07 25 | 353
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.
All process data and parameter settings, even those that are not mapped to
BACnet objects (engineering setting), can be monitored and operated in Xworks
Plus (XWP). BACnet clients only see what is available via BACnet.
If several clients modify the same process data, the last change is accepted.
Volatile and non-volatile process data and parameter settings
The majority of the process data is volatile data, which is recalculated when the
automation stations are restarted. However, certain process data is retained
even after an automation station restart, e.g., self-adaptive control parameters,
run-time totalizers, etc., which are specifically identified as such in a function
block. Even in the event of a program change, this non-volatile process data
remains in memory and can be read back with XWP.