Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide - Manual (Page 39)

Rockwell Automation Publication CNET-IN001C-EN-P - October 2011 39
Topology and Signal Considerations Chapter 2
Maximum Propagation Delay Through a Network
Figure 13 is an example of a maximum propagation delay through a network.
Figure 13 -
.
Calculating the Delays
The example has the following maximum delay path from node 1 to node 2,
end to end.
Delay Path 1: From controller to repeater adapter
Delay 1: 750 m coax cable x 4.17 ns/m = 3127 ns
Delay Path 2: 1786-RPCD module
Delay 2: Coax repeater; 901 ns (1786-RPA/B module) + 100 ns
(1786-RPCD module) =
1001 ns
Delay Path 3: 1000 m of coax cable
Delay 3: 1000 m coax cable x 4.17 ns/m = 4170 ns
Delay Path 4: Fiber repeater; 1786-RPA/B module and 1786-RPFM module
Delay 4: Fiber repeater; 901 ns (1786-RPA/B module) + 153 ns
(1786-RPFM module) = 1054 ns
31417-M
Delay 2 Delay 4 Delay 6 Delay 8
Delay 3
Delay 1
Delay 5 Delay 7
Channel A
Node 1
Node 3 Node 2
750 m
1000 m
3000 m 100 m
Delay 9
20 m 20 m
IMPORTANT Cable delays through taps are minimal and can be ignored.