Rockwell Automation 1756-DHRIO_DHRIOXT ControlLogix Data Highway Plus-Remote I/O Communication Interface Module - Manual (Page 103)

Rockwell Automation Publication 1756-UM514C-EN-P - June 2014 103
Using the 1756-DHRIO and 1756-DHRIOXT Modules in Remote I/O Applications Chapter 9
Trunk Line/Drop Line Considerations
When using a trunk line/drop line configuration, use 1770-SC station
connectors and follow these cable-length guidelines:
• The trunk line-cable length depends on the communication rate of the
link.
• The drop-cable length uses a maximum of 30.4 m (100 cable-ft.).
For daisy chain configurations, use the following table to determine the total
cable length you can use.
For proper operation, terminate the ends of a remote I/O network by using the
external resistors shipped with the 1756-DHRIO and 1756-DHRIOXT
modules. Selecting a 150W or a 82W terminator determines how many devices
you can connect on one remote I/O network.
A remote I/O network using this
communication rate: Cannot exceed this cable length:
57.6 kbps 3,048m (10,000 ft)
115.2 kbps 1,524m (5,000 ft)
230.4 kbps 762m (2,500 ft)
If your remote I/O network: Use this resistor
rating: The maximum
number of physical
devices you can
connect on the
network: The maximum
number of racks you
can scan on the
network:
does not contain any of the devices
listed in the row below, regardless of
communication rate 82
Ω
32 32
contains any of the following:
• 1771-AS
• 1771-ASB/A
• 1771-ASB/B
• 1771-DCM
• 1771-AF 150
Ω
16 16
operates at 57.6kbps or 115.2kbps, and
the network does not support more than
16 physical devices