Processing Produced And Consumed Tags - Allen-Bradley ControlLogix User Manual

See the chapters on scheduled communications for examples of creating
produced/consumed tags and send/receive scheduled messages.

Processing Produced and Consumed Tags

In the producer/consumer model, the consumer is the connection originator
(it opens the connection). When several consumers are trying to open the
connection to the same tag, the connection will be opened to transfer data at
the rate of the consumer with the smallest API (see Actual Packet Interval
on page 1-8).
The producer and consumer must be configured correctly for the specified
data to be shared. To produce for several consumers, the producer must be
configured for this using the RSLogix5000 software for the Logix5550
controller. For the PLC-5C send and receive scheduled messages are
configured using the Map Editing Tool in RSNetWorx for ControlNet.
For ControlLogix controllers, a consumed tag in the consumer must be
specified exactly the same as a produced tag in the producer. In the
following example, consumer_2 does not have the correct tags.
producer
Produced tag names
A
B
C
D
When consumer_2 tries to obtain the shared tags, the connections fail. Even
though three of the tags are specified correctly (B, C, and D), the
connections fail for all the consumed tags because one was incorrect (E).
The other consumers (consumer_1 and consumer_3) can still obtain the
shared tags from the network, as long as their tags are specified correctly.
One consumer failing to obtain shared data does not affect other consumers
accessing the same data.
ControlNet Communication Basics
Consumed tag names
consumer_1
A
B
D
Consumed tag names
consumer_2
E
B
C
D
Consumed tag names
consumer_3
B
C
D
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1756-6.5.3 - December 1999