Allen-Bradley GuardLogix 5570, User Manual

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Rockwell Automation Publication 1756-UM022D-EN-P - May 2017 71
Communicate over Networks Chapter 4
The ControlNet communication modules provide the following:
• Support for messaging, produced/consumed safety and standard tags,
and distributed I/O
• They support the use of coax and fiber repeaters for isolation and
increased distance.
Producing and Consuming Data via a ControlNet Network
The GuardLogix controller supports the ability to produce (send) and
consume (receive) tags over ControlNet networks. The total number of tags
that can be produced or consumed is limited by the number of available
connections in the GuardLogix controller.
Connections over the ControlNet Network
The number of connections the controller uses is determined by how you
configure the controller to communicate with other devices in the system.
Connections are allocations of resources that provide more reliable
communication between devices compared to unconnected messages.
ControlNet connections can be scheduled or unscheduled.
The 1756-CNB and 1756-CNBR communication modules support 64 CIP
connections over a ControlNet network. However, we recommend that you
configure no more than 48 connections to maintain optimal performance.
The 1756-CN2 module supports 128 CIP connections over the ControlNet
network.
Table 21 - ControlNet Connections
Connection Type Description
Scheduled
(unique to the ControlNet network) A scheduled connection is unique to ControlNet communication. A scheduled connection lets you send and receive data repeatedly at a
predetermined interval that is the requested packet interval (RPI). For example, a connection to an I/O device is a scheduled connection
because you repeatedly receive data from the module at a specified interval. Other scheduled connections include connections to the
following:
• Communication devices
• Produced/consumed tags
On a ControlNet network, you must use RSNetWorx for ControlNet software to enable scheduled connections and establish a network
update time (NUT). Scheduling a connection reserves network bandwidth to specifically handle the connection.
Unscheduled An unscheduled connection is a message transfer between controllers that is triggered by the requested packet interval (RPI) or the
program (such as an MSG instruction). Unscheduled messaging lets you send and receive data when needed.
Unscheduled connections use the remainder of network bandwidth after scheduled connections are allocated.
Safety produced/consumed connections are unscheduled.