Understanding The Producer/Consumer Model - Allen-Bradley ControlLogix User Manual

1-4 ControlNet Communication Basics
Understanding the
Producer/Consumer Model
ControlLogix Description
Tag Type
(1) Tags that the controller produced for other
Produced
nodes to consume.
(1) Tags whose values are produced by
Consumed
another controller.
PLC-5C Description
Message Type
Send Scheduled Scheduled data that the PLC-5C produces
for other nodes to consume.
Receive Scheduled data produced by another
Scheduled controller.
(1)
Produced and consumed tags must be controller-scoped tags of DINT or REAL data type, or in an array or structure.
1756-6.5.3 - December 1999
With the RSLogix5000 programming software the path is configured using
the Communication tab in the Message Configuration window. See page
3-5 for an example.
In traditional I/O systems, controllers poll input modules to obtain their
input status. Digital input modules in the ControlLogix system are not
polled by a controller. Instead, the modules produce ("multicast") their data
either upon a change of state or periodically. The frequency of update
depends upon the options chosen during configuration and where on the
network the input module resides. The input module, therefore, is a
producer of input data and the controller is a consumer of the data.
The controller can also produce data for other controllers to consume. The
produced and consumed data is accessible by multiple controllers over the
ControlBus backplane and over the ControlNet network. This data
exchange conforms to the producer/consumer model.
This manual provides examples of the producer/consumer model as it
applies to ControlLogix and PLC-5C controllers.
Note that PLC-5 terminology differs slightly from that used by
ControlLogix. A PLC-5C "send scheduled message" is functionally
equivalent to a ControlLogix "produced tag." A PLC5 "receive scheduled
message" is functionally equivalent to a ControlLogix "consumed tag."
Important:
Specify Using RSLogix5000 Software
Enabled for producing
Number of consumers allowed
Name of controller that owns the tag the local controller wants
to consume
Tag name or instance that the local controller wants to
consume
Data type of the tag to consume
Update interval of how often the local controller consumes the
tag data
Specify Using the Map Editing Tool (MET)
in RSNetWorx for ControlNet
Message number
Message Size
Node number sending the message onto ControlNet
Slot number of the controller that owns the tag the PLC-5C
wants to receive
Tag name or instance that the PLC-5C wants to receive
Requested Packet Interval
Message Size