Rockwell Automation 1756-DH485 ControlLogix DH-485 Communication Module User Manual - Manual (Page 46)

Publication 1756-UM532A-EN-P - May 2006
3-14 Use Data Highway 485 Network
Use the Common Industrial
Protocol (CIP) Messaging Common Industrial Protocol (CIP) is the communication mechanism on
ControlLogix chassis, ControlNet, and EtherNet/IP networks with the
Encapsulation Protocol (EPIC) protocol.
Like DH-485 messaging, CIP supports communication between devices on
the same link and physically separate links. However, CIP messaging uses a
different method to route messages than DH-485 messaging.
CIP uses a relative path concept for routing messaging. Because the message
itself, or the connection the message is sent on, contains all the information
required to route the message, CIP messages do not require any routing table
or link IDs.
Devices such as ControlLogix devices, devices that use the ControlNet
network, and devices that use CIP protocol support this new type of
communication.
IMPORTANT
Your 1756-DH485 module supports bridging CIP
messaging over a DH-485 link. However, your
1756-DH485 module does not support bridging CIP I/O
data from a ControlLogix controller to an 1756-I/O
module.