Omron SYSMAC 3G8F7-CLK12-EV1, Руководство по эксплуатации

Страница: 147 / 188

127
Network Parameters Section 8-1
Polling Cycle The polling cycle is the period during which the polling node checks the status
of the nodes in the network. The polling node checks whether each node is
actually participating in the network, whether there are any new nodes partici-
pating, and so on, and notifies all the nodes of the results of the check.
Refresh Cycle Time The refresh cycle time is the time, during data link operation, from when the
contents of the data link areas are refreshed until the next time they are
refreshed. The refresh cycle time will vary depending on factors such as the
communications 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 Sup-
port Board is read by the Controller Link Support Software, therefore, the
value will always be 0.
8-1-3 Network Parameters
Network parameters are also used to control network operations. Network
parameters 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 net-
work always have the same network parameter settings. If nodes are con-
nected to the network halfway during network operation, the network
parameter settings will also be distributed to these nodes when they are con-
nected. The following three network parameters can be specified.
Maximum Node Address 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
operations. 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.
No. of Polled Nodes Per
Communications Cycle
This parameter specifies the number of nodes to be checked (polled) by the
polling 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 required to recognize that nodes have been removed from or added to
the network. Reducing the setting of this parameter shortens the communica-
tions cycle time but delays a network response when a node is disconnected
from or connected to the network.
No. of Event-frames per
Communications Cycle
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
error.
See
8-2 Communications Cycle Time
for the effects of network parameters on
communication cycle times.