Rockwell Automation 1756-L6x_L7x ControlLogix System User Manual - Manual (Page 110)

110 Rockwell Automation Publication 1756-UM001O-EN-P - October 2014
Chapter 6 Serial Communication on 1756-L6x Controllers
DH-485 Protocol The controller can send and receive messages to and from other controllers on a
DH-485 network. The DH-485 connection supports remote programming and
monitoring via the Logix Designer application. However, excessive traffic over a
DH-485 connection can adversely affect overall controller performance and lead
to timeouts and decreased performance of the configuration.
You can also use a 1756-DH485 module to connect the ControlLogix chassis to a
DH-485 network with multiple controllers. For more information, see the
ControlLogix DH-485 Communication Module User Manual, publication
1756-UM532 .
The DH-485 protocol uses RS-485 half-duplex as its physical interface. RS-485
is a definition of electrical characteristics, not a protocol. You can configure the
RS-232 port of the ControlLogix controller to act as a DH-485 interface.
To connect the controller to the DH-485 network, you must use these
components:
• A 1761-NET-AIC converter (two controllers can be connected to one
converter)
• An RS-232 cable (catalog number 1756-CP3 or 1747-CP3) for each
controller to connect to the converter
IMPORTANT Use Logix5000 controllers on DH-485 networks only when you want to add
controllers to an existing DH-485 network.
For new applications with Logix5000 controllers, we recommend that you
use networks in the NetLinx open architecture.