Install repeaters in a ring – Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide User Manual

Page 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).

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-RPFRXL

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