MVI56E-FLN ♦ ControlLogix Platform
Reference
FA Control Network Ethernet Communication Module
User Manual
ProSoft Technology, Inc.
Page 93 of 155
Cyclic Transmission
Cyclic transmission is used to exchange data between nodes. The data is shared
by each node through the Common Memory (shared memory) function.
Basic functions:
Cyclic transmission implements Common Memory interface.
Each node transmits its entire memory content while it holds the token.
Nodes having no cyclic data are acceptable.
With cyclic communications, the Common Memory is refreshed on a fixed cycle
time. Message communications are controlled so that the Common Memory
refresh time does not exceed the allowable refresh cycle time.
Each node constantly monitors the message communications frames that travel
through the network from the time it receives one local-node-directed token until
it receives the next local-node-directed token. When no message
communications frame travels through the network in a single cycle, 120% of the
cycle time value becomes the allowable refresh cycle time. In this way the
allowable refresh cycle time is actively determined according to the number of
nodes in the network.
