Rockwell Automation 5720 DriveLogix System - Manual (Page 164)

Publication 20D-UM002C-EN-P - November 2003
7-18 Communicating with Devices on a ControlNet Link
The producer and consumer must be configured correctly for the specified
data to be shared. A produced tag in the producer must be specified exactly the
same as a consumed tag in the consumer.
If any produced/consumed tag between a producer and consumer is not
specified correctly, none of the produced/consumed tags for that producer
and consumer will be transferred. However, other consumers can still access
their shared tags, as long as their tags are specified correctly. One consumer
failing to access shared data does not affect other consumers accessing the
same data.
Maximum number of produced and consumed tags
The maximum number of produced/consumed tags that you can configure
depends on the connection limits of the communication device that transfers
the produced/consumed data.
Each produced tag uses one connection for the tag and the first configured
consumer of the tag. Each consumer thereafter uses an additional connection.
Size limit of a produced or consumed tag
A produced or consumed tag can be as large as 488 bytes, but it must also fit
within the bandwidth of the ControlNet network:
• As the number of connections over a ControlNet network increases,
several connections, including produced or consumed tags, may need to
share a network update.
• Since a ControlNet network can only pass 500 bytes in one update, the
data of each connection must be less than 488 bytes to fit into the
update.
If a produced or consumed tag is too large for your ControlNet network, make
one or more of the following adjustments:
• Reduce the Network Update Time (NUT). At a faster NUT, less
connections have to share an update slot.
• Increase the Requested Packet Interval (RPI) of all connections. At a
higher RPI, connections can take turns sending data during an update
slot.