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Network Parameters
8-1-3 Network Parameters
Maximum Node Address
No. of Polled Nodes Per
Communications Cycle
No. of Event-frames per
Communications Cycle
8-1-4 Specifying Network Parameters
The refresh cycle time will vary depending on factors such as the communica-
tions cycle time, the number of data link words, and so on.
The refresh cycle time value can be displayed by the Controller Link Support
Software's data link status monitoring function. There is no refresh cycle time for
the Support Board, because the data link areas are constantly refreshed by the
data link data that is received. When the refresh cycle time for the Support Board
is read by the Controller Link Support Software, therefore, the value will always
be 0.
Network parameters are also used to control network operations. Network pa-
rameters are read from the polling node and distributed to all other nodes when
the Controller Link Network is started. In this way, all nodes on the network al-
ways have the same network parameter settings. If nodes are connected to the
network halfway during network operation, the network parameter settings will
also be distributed to these nodes when they are connected. The following three
network parameters can be specified.
This parameter specifies the maximum node address of nodes to be checked by
the polling node. The default is 32 for Wired Networks and 62 for Optical Ring
Networks Reducing the setting of this parameter reduces the number of nodes
checked by the polling node and can thus avoids unnecessary check opera-
tions. However, if the network contains nodes with node addresses greater than
the setting of the parameter, these nodes will not be connected to the network.
This parameter specifies the number of nodes to be checked (polled) by the pol-
ling node during each polling cycle. The default is 4. Setting this parameter to a
high value increases the communications cycle time, but reduces the time re-
quired to recognize that nodes have been removed from or added to the net-
work. Reducing the setting of this parameter shortens the communications cycle
time but delays a network response when a node is disconnected from or con-
nected to the network.
This parameter specifies the maximum number of event frames (communica-
tions other than data links, such as message service transmissions) that can be
transferred during a communications cycle. Specify a value in units of 128 bytes.
The default is 35 (128 35 = 4,480 bytes).
Increasing the setting of this parameter increases the communications cycle
time but allows for more event communications such as the message service.
Too small a parameter value restricts event communications, resulting in an er-
ror.
See 8-2 Communications Cycle Time for the effects of network parameters on
communication cycle times.
The network parameters can be specified from the Controller Link Support Soft-
ware. This section describes only the allowable setting range for each network
parameter. Refer to the Controller Link Support Software Operation Manual
(W308) for setting procedures.
The following table shows the setting range and default for network parameters.
Network parameter
Maximum node address
Number of polled nodes per communications cycle
No. of event-frames per communications cycle
Section
8-1
Setting
Default
range
value
2 to 62
62 (See
note 1.)
1 to 61 (See
4
note 2.)
16 to 238
35
115
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