124 Rockwell Automation Publication 1756-UM001M-EN-P - February 2012
Chapter 7 Manage Controller Communication (connections)
The system-shared tags are explained in this table.
For two controllers to share produced or consumed tags, both must be attached
to the same network. You cannot bridge produced and consumed tags over two
networks.
Produced and consumed tags use connections of both the controller and the
communication modules being used. For a ControlNet network, produced and
consumed tags use scheduled connections.
Connection Requirements of a Produced or Consumed Tag
Produced and consumed tags each require connections. As you increase the
number of controllers that can consume a produced tag, you also reduce the
number of connections the controller has available for other operations, like
communication and I/O.
Each produced or consumed tag uses the number of connections listed in this
table. Adding status information to a produced/consumed tag does not impact
the number of connections used.
Table 31 - Produced and Consumed Tag Definitions
Tag Definition
Produced tag A tag that a controller makes available for use by other controllers. Multiple controllers
can simultaneously consume (receive) the data. A produced tag sends its data to one or
more consumed tags (consumers) without using logic.
Consumed tag A tag that receives the data of a produced tag. The data type of the consumed tag must
match the data type (including any array dimensions) of the produced tag. The RPI of
the consumed tag determines the period at which the data updates.
If a consumed-tag connection fails, all of the other tags being consumed
from that remote controller stop receiving new data.
Table 32 - Produced and Consumed Tag Connections
This Type of Tag Uses This Many Connections Of This Module
Produced tag number_of_configuredconsumers + 1 Controller
Consumed tag 1
Produced or consumed tag 1 Communication
Calculations of Connections for Produced or Consumed Tags
• A ControlLogix controller producing 4 tags for 1 controller uses 8 connections:
– Each tag uses 2 connections (1 consumer + 1 = 2).
– 2 connections per tag x 4 tags = 8 connections.
• Consuming 4 tags from a controller uses 4 connections (1 connection per tag x 4 tags
=4connections).
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