Echelon Mini EVK - Manual (Page 73)

Feedback loops allow for tied control; the lamp can for example sense the
light level and provide the feedback signal based on real measurement
(rather than assumption).
Simple feedback loops contain a single source and a single destination. Creating
the feedback connection is straight-forward, as shown in Figure 4.5.
Figure 4.5 Simple Feedback Loops
With multiple sources or destinations, however, two distinct shapes of feedback
connections are possible: a daisy-chained feedback connection, and a star-shaped
feedback connection. These are shown in Figures 4.6 and 4.7
Figure 4.6 Daisy-chained Feedback Connection
Figure 4.7 Star-shaped Feedback Connection
The daisy-chained feedback loop is often considered inferior, mostly because the
loop breaks as a result of a single failure in the entire chain (subject to the
application, this might actually be desirable behaviour), and also due to the fact
that changes take time to propagate through the chain. For example, a large
number of lights will not change the state simultaneously, but one after the
other.
However, an outstanding advantage of the daisy-chain feedback loop is the
simple and elegant transport control provided. The initiator device (switch B, for
example) only needs to await exactly one feedback network variable update to
know the loop has been completed.
Mini EVK User’s Guide 67