Omron CJ1W-EIP21 用户手册

In an Ethernet network using a switching hub, the network bandwidth is not
shared by all of the nodes; independent transmission paths are established
between individual nodes through the switching hub.

A dedicated communications buffer is established in the switching hub for
communications between the nodes and full-duplex communications (simulta-
neous 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 communications can be performed.

The switching hub functions shown in the following table determine the perfor-
mance of tag data links.

The following table shows the tag data link settings that can be made for indi-
vidual EtherNet/IP Units as well as the setting ranges.

When the tag data link settings exceed the capabilities of the switching hub
being used, increase the RPI value. Particularly when using a switching hub
that does not support multicast filtering, the settings must be made consider-
ing that multicast packets will be sent even to nodes without connection set-
tings. 

In addition, if the required tag data link performance cannot be achieved with
the switching hub’s capabilities, reevaluate the overall network configuration
and correct it by taking steps such as selecting a different switching hub 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.

If the Network Configurator is used to set the connection type in the connec-
tion settings to a multicast connection, multicast packets will be used. If the
connection type is set to a point-to-point connection, multicast packets will not
be used.

Buffer capacity

This is the amount of data that can be buffered when packets 
accumulate at the switching hub.

Multicast filtering

This function transfers multicast packets to specific nodes 
only.

QoS function

This function performs priority control on packet transfers.

Network bandwidth

Physical Ethernet baud rate

100 Mbps or 10 Mbps

Allowed tag data link 
communications band-
width

Maximum number of tag data 
link packets that can be pro-
cessed in 1 second (pps: pack-
ets per second)

CJ2M: 3,000 pps max.
Other CPU Units: 6,000 
pps max. 

Connection resources

Number of connections that can 
be established

CJ2M: 32 max.
Other CPU Units: 
256 max. 

Packet interval 
(RPI: Requested Packet 
Interval)

Refresh cycle for tag data

CJ2M: 1 to 1,000 ms
Other CPU Units: 
0.5 to 10,000 ms

(in 0.5 ms units)