Omron SYSMAC CJ1W-EIP21, Operation Manuals

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7 Tag Data Link Functions
7-10
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
Setting the Requested Packet Interval (RPI)
The RPI is the data I/O refresh cycle on the Ethernet line when performing tag data links. The RPI
can be set separately for each connection. You can set the EtherNet/IP Unit to between 0.5 and
10,000 ms (in 0.5-ms increments). The default setting is 50 ms. With EtherNet/IP, data is exchanged
on the communications line at the packet interval that is set for each connection, regardless of the
number of nodes.
Setting Multi-cast and Unicast Communications
You can select a multi-cast connection or unicast (point-to-point) connection as the connection type
in the tag data link connection settings. With a multi-cast connection, you can send an output tag set
in one packet to multiple nodes and make allocations to the input tag sets. A unicast connection sep-
arately sends one output tag set to each node, and so it sends the same number of packets as the
number of input tag sets. Therefore, multi-cast connections can decrease the communications load
if one output tag set is sent to multiple nodes. If multi-cast connections are used, however, use an
Ethernet switch that has multi-cast filtering, unless the tag set is received by all nodes in the net-
work. If an Ethernet switch without multi-cast filtering is used, the multi-cast packets are broadcast to
the entire network, and so packets are sent to nodes that do not require them, which will cause the
communications load on those nodes to increase. To use a multi-cast connection and send an out-
put tag set in one packet to multiple nodes, the following settings for the receiving node must be the
same as the settings of the sending node: the connection type (multi-cast), the connection I/O types,
packet internals (RPI), and timeout values.
Precautions for Correct Use Precautions for Correct Use
The performance of communications devices is limited to some extent by the limitations of each
product’s specifications. Consequently, there are limits to the packet interval (RPI) settings. Refer
to 12-2 Adjusting the Communications Load and set an appropriate packet interval (RPI).
Tag data links are automatically started when the data link parameters are downloaded from the Net-
work Configurator and the power supply to the NJ-series Controller is turned ON. Thereafter, you can
start and stop tag data links for the entire network or individual devices from the Network Configurator.
Starting and stopping tag data links for individual devices must be performed for the originator. Further-
more, you can use the device variables for the CJ-series Unit to start and stop the entire network. Refer
to 7-2-12 Starting and Stopping Tag Data Links for details.
You can include the Controller status as a member of a tag set in the data sent and received.
The Controller status consists of flags that show the operating status of the CPU Unit to which the Eth-
erNet/IP Unit is mounted. It includes operating information and error information. If the Controller status
is specified as an output (send) tag, the Controller status is added to the start of the tag set in the fol-
lowing format. (Select the Include Option for the Controller Status in the upper right of the Edit Tag Set
Dialog Box.)
To receive the Controller status, specify the Controller status for the In - Consume Tab Page in the dia-
log box used to edit the receive tag set. (Select the Include Option for the Controller Status in the upper
right of the Edit Tag Set Dialog Box.) When a tag data link is started, the contents of the Controller sta-
tus is stored in the device variables for the CJ-series Unit that are given below.
7-1-5 Starting and Stopping Tag Data Links
7-1-6 Controller Status
Controller Error Flag
Controller Operating Flag
0 0 0 0 0 0 0 0 0 0 0 0 0 0
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0