Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide - Manual (Page 18)

18 Rockwell Automation Publication CNET-IN001C-EN-P - October 2011
Chapter 1 Get Started with the ControlNet Network Fiber Media System
Ring Topology
A ring topology provides redundancy by providing two data paths in a single ring.
A ring can sustain two faults before that data connection is lost. You should
consider a ring when your devices (Controller and I/O) are single port (A only)
and media redundancy is required. Only the 1786-RPFRL and 1786-RPFRXL
repeater modules support ring topologies.
In a ring topology on the ControlNet network, you can use:
• Up to 5 repeaters by using one 1786-RPA/A repeater adapter.
• The 1786-RPA/B repeater adapter allows for a maximum of 20
1786-RPFRL (long distance) or 1786-RPFRL/X (extra long-distance)
ring repeaters.
Figure 4 - Ring Topology
If a ring is broken, the configuration then becomes a linear bus and the number of
repeaters in SERIES depends on where the ring is broken. You will have as many
repeaters as in the original ring.
See page 29 to determine different topology constraints.
Up to 20 1786-RPFR(X)L
repeaters on a fiber ring.
Fi
be
r
Fib
er
Fiber
Fibe
r
Fiber
Fib
er
Fi
be
r
Node(s)
Node(s)
Node(s) Node(s)
Node(s)
Node(s)
Node(s)
RPA +
RPFRXL
RPA +
RPFRXL
RPA +
RPFRXL
RPA +
RPFRXL
RPA +
RPFRXL
RPA +
RPFRXL
RPA +
RPFRXL
Coax
Coax
Coax
Coax
Coax
Coax
Coax
Coax Network
Coax Network