Allen-Bradley ControlLogix 1756-DH485, User Manual, Page: 35 / 110

Publication 1756-UM532A-EN-P - May 2006
Use Data Highway 485 Network 3-3
Use DH-485 Messaging
DH-485 Messaging offers the following benefits:
•
You can send messages between devices on the same link.
•
You can send messages between devices on different links.
DH-485 messaging is divided into two types:
•
Local DH-485 Messaging - See page 3-3
•
Remote DH-485 Messaging - See page 3-5
Before you can design a control system to meet your application needs, be
aware of the difference between Local DH-485 Messaging and Remote
DH-485 Messaging.
Local DH-485 Messaging
Devices use local DH-485 messaging to communicate between devices on the
same physical link. A device that uses local DH-485 messaging must:
•
generate local DH-485 packets.
•
support local DH-485 protocol.
•
send and receive messages.
TIP
SLC 5/01 controller receives and replies, but does not
initiate.