Adjusting The Communications Load - Omron CJ1W-EIP21 Operation Manuals

12 Communications Performance and Communications Load

12-2 Adjusting the Communications Load

In an Ethernet network using an Ethernet switch, the network bandwidth is not shared by all of the
nodes; independent transmission paths are established between individual nodes through the Ethernet
switch.
A dedicated communications buffer is established in the Ethernet switch for communications between
the nodes and full-duplex communications (simultaneous transmission and reception) are performed
asynchronously with other transmission paths. The communications load in other transmission paths
does not affect communications, so packet collisions do not occur and stable, high-speed communica-
tions can be performed.
The Ethernet switch functions shown in the following table determine the performance of tag data links.
Item
Buffer capacity
Multicast filtering
QoS function
The following table shows the setting ranges of the tag data link settings that can be made for an Ether-
Net/IP Unit.
Network bandwidth
Allowed tag data link communications
bandwidth
Connection resources
Packet interval (RPI: Requested
Packet Interval)
When the tag data link settings exceed the capabilities of the Ethernet switch being used, increase the
packet interval (RPI) value. Particularly when using an Ethernet switch that does not support multicast
filtering, the settings must be made considering that multicast packets will be sent even to nodes with-
out connection settings.
Additional Information
If the Network Configurator is used to set the connection type in the connection settings to a mul-
ticast connection, multicast packets will be used. If the connection type is set to a point-to-point
connection, multicast packets are not used.
In addition, if the required tag data link performance cannot be achieved with the Ethernet switch's
capabilities, re-evaluate the overall network configuration and correct it by taking steps such as select-
ing a different Ethernet switch or splitting the network.
The following sections show how to check the device bandwidth being used by the tag data links in the
designed network, and how to set the appropriate values.
12-6
This is the amount of data that can be buffered when packets accumulate at
the Ethernet switch.
This function transfers multicast packets to specific nodes only.
This function performs priority control on packet transfers.
Item
Physical Ethernet baud rate
Maximum number of tag data link
packets that can be processed in 1
second (pps: packets per second)
Number of connections that can be
established
Refresh period for tag data
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
Description
Description
100 Mbps or 10 Mbps
6,000 pps max.
256 max.
0.5 to 10,000 ms in 0.5-ms
increments
Settings