FOE topologies - Daisy chain topology
A daisy chain topology allows the remote I/O connection to be extended and can be utilized several
times - if maximum flight delay times of data passing between the C300 controller and I/O are not
exceeded.
When Series C daisy chaining,
the electrical port requires no interface cable to be attached. This applies if:
l daisy chaining Series-C link traffic, and
l I/O is not present at the repeating location.
When PM I/O daisy-chaining,
an interface cable must always be connected to the electrical port. This is because the cable keys
the FOE for the PM mode of operation
A repeater function also extends the remote I/O similar to the daisy chain technique, but relies on
the optical ports of two FOE modules to provide the interconnection.
13.4.6 FOE topologies - Star topology
The figures below illustrate the STAR topology whereby remote FOE nodes are individually
connected to a central connection point (e.g. the C300). This topology has the advantage in that if
one cable or cable set fails, the rest of the remote nodes remain operational. For this reason STAR
is the most widely used configuration. The STAR is sometimes referred to as a chicken foot
topology.
13.4.7 Maximum flight delay times
The I/O link communication protocol imposes a constraint between the C300 controller and the
most distant I/O location, known as maximum flight delay time. This places a limit on the combined
number of FOEs, and cumulative fiber cable length permitted in any IOL path. Note that these
flight delay times constrain the distance regardless of the use of multi-mode versus single-mode
fiber. In another words, the maximum distance are stated below regardless of the use of multimode versus single-mode fiber. This constraint varies for:
Series C - maximum cable length is 10 km
PM I/O - maximum cable length is 8 km
