Publication 1756-UM514B-EN-P - February 2003
Using the Data Highway Plus Network 2-7
Local DH+ Messaging
Devices use local DH+ messaging to communicate between devices
on the same physical link. A device that uses local DH+
messaging
must:
· generate local DH+ packets.
· support local DH+ protocol.
· send and receive messages.
A local DH+ message sent on a DH+ network has only enough
address information to get the message to a target node on the same
DH+ network.
The example in Figure 2.2 shows a PLC-5 sending a message to port A
on the 1756-DHRIO module. Because the controller slot for port A is
configured to “0”, the message is forwarded to the ControlLogix
controller in slot
0.
Figure 2.2
1756- DHRIO
PLC-5 processor B
node number: 025
Channel A
node number: 010
controller slot=0
ControlLogix controller
41458
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