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5.1.5 Transfer cycle and monitoring
In cyclic data communication, the common memory is refreshed at virtually fixed intervals.
Message transmission is controlled to prevent a single message communication from causing the
time limit on the common memory refresh cycle to be exceeded.
Each node constantly monitors message communication frames flowing within the network
during the time interval between the reception of a token addressed to itself and the reception of
the next token addressed to itself. When no message communication frame flows within the
network during such one cycle, 120 percent of the duration of one such cycle is used as the
refresh cycle time limit.
Thanks to the above monitoring process, the refresh cycle time limit is dynamically determined
by the number of participating nodes within the network.
Example: When only cyclic data communication is maintained by five nodes (no message
communication is effected by any nodes)
Node
1
For the calculation procedure, see "5.3.7 FL-net module communication performance."
Token
Cyclic data
Node
2
The time interval between a reception by node
1 and the next reception by node 1 is measured
(measured refresh cycle time) while nodes 1 to
5 are engaged in cyclic data communication
only, and 120 percent of the measured value is
regarded as the refresh cycle time limit.
Figure 5-10 Typical Refresh Cycle Time Limit
FL-net
Node
Node
3
5-7
5 USER GUIDE
Node
4
5
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