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SECTION 10
Communications Performance and Communications Load
This section describes the communications performance in an EtherNet/IP network, and shows how to estimate the I/O
response times and transmission delays.
10-1 Communications System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
10-1-1 Tag Data Link Communications Method . . . . . . . . . . . . . . . . . . . . . 262
10-1-2 Calculating the Number of Connections. . . . . . . . . . . . . . . . . . . . . . 264
10-1-3 Network Transmission Delay Time . . . . . . . . . . . . . . . . . . . . . . . . . 265
10-2 Adjusting the Communications Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
10-2-1 Checking Bandwidth Usage for Tag Data Links . . . . . . . . . . . . . . . 269
10-2-2 Tag Data Link Bandwidth Usage and RPI . . . . . . . . . . . . . . . . . . . . 270
10-2-3 Adjusting Device Bandwidth Usage. . . . . . . . . . . . . . . . . . . . . . . . . 271
10-2-4 Changing the RPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
10-2-5 RPI Setting Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
10-3 I/O Response Time in Tag Data Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
10-3-1 Timing of Data Transmissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
10-3-2 EtherNet/IP Unit or CJ2H Built-in Port Data Processing Time . . . . 283
10-3-3 Effect on the CPU Unit’s Cycle Time. . . . . . . . . . . . . . . . . . . . . . . . 284
10-3-4 Tag Data Link I/O Response Time Calculation Example. . . . . . . . . 285
10-4 Tag Data Link Performance for CJ2M Built-in EtherNet/IP Ports. . . . . . . . . 291
10-4-1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
10-4-2 Tag Data Link I/O Response Time . . . . . . . . . . . . . . . . . . . . . . . . . . 292
10-5 Message Service Transmission Delay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
10-5-1 Maximum Transmission Delays (Excluding Delays in the Network) 294