Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide - Manual (Page 24)

24 Rockwell Automation Publication CNET-IN001C-EN-P - October 2011
Chapter 1 Get Started with the ControlNet Network Fiber Media System
Install Repeaters in a Ring
Use this configuration to achieve an increased level of protection (in case of
cable failure) over a long distance (not available when you use traditional
copper media). To achieve this increased level of protection, a fiber ring network
transmits messages in the two directions of the ring (clockwise and
counter-clockwise).
In Figure 8 , the path from node 1 to node 4 in a counter-clockwise direction is
through 2 fiber repeaters (A, D). In a clockwise direction, the path from node 1 to
node 4 is though 4 fiber repeaters (A, B, C, D). We refer to the longer path as the
worst-case delay path.
Figure 8 - Fiber Repeaters in a Ring
The 1786-RPFRXL/B and 1786-RPFRL/B fiber repeaters automatically detect
which message arrives first and disregards the other at each fiber repeater
location. In the above example, the 1786-RPFRXL fiber repeater for node 4
would automatically detect the packet that arrives on a channel first, and
disregard the second packet.
Node 1
Node 2
Node 3
Node 4
31237-M
1794-ACNR15 1786-RPA 1786-RPFRXL
1786-RPA
1786-RPA
1786-RPA
1786-RPFRXL
1786-RPFRXL
1786-RPFRXL
1794-ACNR15
1794-ACNR15
Repeater A
Repeater B
Repeater C
Repeater D
Fiber Cable 1
Fiber Cable 2
Coax Segment 1
Coax Segment 2
Coax Segment 3
Coax Segment 4
Fiber Cable 3
Fiber Cable 4