Publication 1756-UM514B-EN-P - February 2003
2-10 Using the Data Highway Plus Network
Remote DH+ Messaging
Devices use remote DH+ messaging to communicate between devices
on physically separate networks. A device that uses remote DH+
messaging must be able to:
· generate Remote DH+ packets.
· support Remote DH+ protocol.
· send and receive messages.
Remote DH+ messaging should be used when:
· the message originating device or the message target device is
one of the devices listed in
Table 2.3 on page 2-4.
· there is a DH+ link in the message’s path from originator to
target.
· the message originating device and the message target device
are on separate networks or the message target is in a
ControlLogix chassis and there is more than one ControlLogix
controller target in the chassis.
Figure 2.3 shows an example of remote DH+ messaging between PLC
processor A and PLC processor B. In this example, the following
information must be included in the remote DH+ message routing
message instruction:
· local DH+ node = 020
· destination link ID = 2
· remote DH+ node = 030
Figure 2.3
ControlLogix chassis
1756-DHRIO module
PLC-5/25 processor A - node:010
Link ID 1
PLC-5 processor B - node: 030
41363
Link ID 2
Channel A - node: 020
Channel B - node: 025
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