Rockwell Automation 1785-Lx0C15 ControlNet PLC-5 Programmable Controllers User Manual - Manual (Page 52)

1785-UM022C-EN-P - February 2008
2-14 Planning to Use Your ControlNet PLC-5 Processor
Understanding Multicast Inputs
This feature enables input devices to send the same data to multiple
processors simultaneously.
Advantages of multicast inputs include:
• Network optimization - reduces network usage since data is sent
only once simultaneously to all connections. This reduction may
allow more complex scheduled connection configurations or
improved unscheduled connection performance.
• Device synchronization - inputting data to all devices
simultaneously improves synchronization between devices
In the following example, the ControlNet PLC-5 processor at node 2
is sending outputs to the adapter at node 3. Nodes 1, 2, and 4 are all
receiving the same input packet from node 3. Nodes 1 and 4 are
considered listen-only and are producing heartbeats to keep their
connections to the adapter alive.
Understanding Multicast Outputs
This feature enables the PLC-5 to simultaneously send the same
output data to more that one target device. To use this feature, both
the PLC-5 and the target devices must support multicast outputs.
Advantages of multicast outputs include:
• Network optimization - reduces network usage since data is sent
only once simultaneously to all connections. This reduction may
allow more complex scheduled connection configurations or
improved unscheduled connection performance.
• Device synchronization - outputting data to all devices
simultaneously improves synchronization between devices
Heartbeat Connection Heartbeat Connection
Point-to-Point Outputs
ControlNet PLC-5
Processor
Node 1 ControlNet PLC-5
Processor
Node 2
ControlNet Adapter
Node 3
ControlNet PLC-5
Processor
Node 4
Multicast Inputs