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- Isn’t Fieldbus too slow, 31.25 kbit/s compared to several Mbit/s
for DCS?
In
Fieldbus there are typically only 12 device per segment (on a pair of
wires) whereas on a DCS all the device of the entire plant are indirectly
connected to a single bus which therefore must be faster.
In order to transfer all link and supervisory data fast enough to get
tight closed loop control and fast MMI (Man-Machine Interface, such as
an operator console) screen update, Fieldbus implements a number features
for communication optimisation.
•
Automatic distributed alarm detection and notification
• Distributed Trending
• Parameter view object groups
• Scheduling
• Update event notification
Thanks
to the mechanisms for passing of configuration, alarm and trend data this
so-called background traffic has been reduced to a minimum leaving more
time for operational traffic and again improving control performance.
After configuration, the system resolves tags and parameter names into
a format, which minimises communication.
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