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Communications System Section 10-1
10-1 Communications System
10-1-1 Tag Data Link Communications Method
Packet Interval (RPI)
Settings
In EtherNet/IP tag data links, the data transmission period is set for each con-
nection as the packet interval (RPI). The target device will send data (i.e., out-
put tags) once each packet interval (RPI), regardless of the number of nodes.
Also, the heartbeat frame is sent from the originator to the target for each con-
nection. The target uses the heartbeat to check to see if errors have occurred
in the connection with the originator. The data transmission period of the
heartbeat frame depends on the packet interval (RPI) settings.
■ Heartbeat Frame Transmission Period
• Packet interval < 100 ms
The heartbeat frame transmission period is 100 ms.
• Packet interval ≥ 100 ms
The heartbeat frame transmission period is the same as the RPI.
Example
In this example, 2 tag data link connections are set for node 2 (the originator)
and node 1 (the target).
The packet interval (RPI) for output data 1 is set to 10 ms.
The packet interval (RPI) for output data 2 is set to 15 ms.
In this case, output data 1 is sent from node 1 to node 2 every 10 ms, and out-
put data 2 is sent from node 1 to node 2 every 15 ms, as shown in the follow-
ing diagram. Also, data is sent from node 2 (the originator) to node 1 (the
target) with a heartbeat of 100 ms for connection 1 and a heartbeat of 100 ms
for connection 2.
10 ms
10 ms
15 ms
Originator
Target
Connection 1 heartbeat
Connection 2 heartbeat
100-ms interval
100-ms interval
Node 1
Node 2
Output data 1
Output data 2
Output data 1
Output data 2
Output data 1