Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide - Manual (Page 28)

28 Rockwell Automation Publication CNET-IN001C-EN-P - October 2011
Chapter 2 Topology and Signal Considerations
Figure 9 - Basic Fiber Media Topology
This configuration is equivalent to the use of a coax repeater. Fiber cable can
provide communication over longer distances than coax media.
Redundant Media Use redundant media when you need module and media redundancy. With
redundant media, the channel-to-channel skew travel time difference must be
less than 1.6
μ
s.
To keep skew time to a minimum, configure the cable paths on channels A and B
in a similar manner as shown in
Figure 10 on page 29 .
Media redundancy can be achieved via a ring topology or linear bus topology.
The 1786-RPFRL/B and 1786-RPFRXL/B fiber repeaters can provide media
redundancy in a ring or linear bus topology, but not both. A redundant linear bus
topology can be obtained by using the 1786-RPFS, 1786-RPFM, and
1786-RPCD repeater modules. The planning phase should consider the
advantages and disadvantages of using a ring or redundant linear bus topology.
Tap
Coax Segment 1
Fiber Repeater
Module
30688-M
Fiber Repeater
Module
Repeater Adapter
Repeater Adapter
Coax Segment 2
Terminator
Fiber Cable
TIP If you use a ring topology to provide media redundancy, you can connect
to only one channel (A or B) of redundant port modules. ControlNet does
not support mixed (linear and ring) redundancy in the same network.
When using linear bus redundancy all ControlNet modules must have
redundant ports (A and B) and must be connected throughout
the network.