Rockwell Automation 1756-DH485 ControlLogix DH-485 Communication Module User Manual - Manual (Page 37)

Publication 1756-UM532A-EN-P - May 2006
Use Data Highway 485 Network 3-5
Limitations of Local DH-485 Messaging
When using Local DH-485 Messaging, you must remember:
• the DH-485 message contains only a node ID for a node on the
DH-485 network.
• a local DH-485 message sent to the node ID of a port on the
1756-DH485 module is forwarded to a single user-configured controller
slot.
• messages on one DH-485 network cannot be routed to other networks.
Logix controllers message via a NetLinx network through a ControlLogix
gateway to DH-485 network to all MicroLogix and SLC 5/03 (and above)
controllers on DH-485 network. RSLinx Classic on DH-485 network can
browse through ControlLogix gateway to any device on NetLinx network.
Remote DH-485 Messaging
Devices use remote DH-485 messaging to communicate between devices on
physically separate networks. A device that uses remote DH-485 messaging
must be able to:
• generate Remote Data Highway 485 network packets.
• support Remote Data Highway 485 network protocol.
• send and receive messages.
Remote DH-485 messaging should be used when:
• The message originating device or the message target device is one of
the supported devices.
Refer to table Types of Communication on the 1756-DH485 Module
on page 3-2.
• There is a DH-485 network link in the message’s path from originator to
target.
• The originating and the target devices are on separate networks
communicating through a ControlLogix gateway.
IMPORTANT
Logix controllers on NetLinx network will not be able to
message through ControlLogix gateway to DH-485
network to fixed SLC 500, SLC 5/01, or SLC 5/02
controllers on DH-485 network.