Rockwell Automation 1756-L6x_L7x ControlLogix System User Manual - Manual (Page 121)

Rockwell Automation Publication 1756-UM001O-EN-P - October 2014 121
Manage Controller Communication Chapter 7
Each produced or consumed tag uses the number of connections that are listed in
Table 27 . Adding status information to a produced/consumed tag does not affect
the number of connections used.
.
The number of available connections limits the number of tags that can be
produced or consumed. If the controller uses its connections for I/O and
communication devices, no connections are left for produced and consumed tags.
For more information about produced/consumed tags, see the Logix5000
Controllers Produced and Consumed Tags Programming Manual, publication
1756-PM011 .
Send and Receive Messages Messages transfer data to other devices, such as other controllers or operator
interfaces. The MSG instruction is a ladder logic output instruction that
asynchronously reads or writes a block of data to or from another module over
Table 27 - 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
EXAMPLE 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 = 4 connections).
Table 28 - ControlLogix Modules and Available Connections
Module Type Cat. No. Available Connections
Controller 1756-L7x 500
1756-L6x 250
EtherNet/IP • 1756-EN2F
• 1756-EN2T
• 1756-EN2TXT
• 1756-EN2TR 256
• 1756-ENBT
• 1756-EWEB 128
ControlNet • 1756-CN2
• 1756-CN2R
• 1756-CN2RXT 128
• 1756-CNB
• 1756-CNBR 64