Allen-Bradley controllogix 1756-L55M12, Руководство пользователя

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Publication 1756-UM001G-EN-P - January 2007
Communicate over Networks 27
ControlNet Network Overview
Connections Over a ControlNet Network
You indirectly determine the number of connections the controller
uses by configuring 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
ControlNet Network
Distributed I/O
1756-CNB Module
(as an adapter) with
1756 I/O Modules
1794-ACN15 Adapter
with 1794 I/O Modules
Workstation
CompactLogix Controller
FlexLogix Controller with
1788-CNC Card
1734-ACNR Adapter with
1734 I/O Modules
PanelView Terminal
PLC-5/40C Controller
PowerFlex 700S AC
Drive with DriveLogix
Connection Definition
Scheduled
(unique to a
ControlNet
network)
A scheduled connection is unique to ControlNet communication. A scheduled connection lets you send and receive data
repeatedly at a predetermined interval, which is the requested packet interval (RPI). For example, a connection to an I/O
module is a scheduled connection because you repeatedly receive data from the module at a specified interval. Other
scheduled connections include connections to:
•
communication devices.
•
produced/consumed tags.
On a ControlNet network, you must use RSNetWorx for ControlNet software to enable all 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 a MSG instruction. Unscheduled messaging lets you send and receive data when you need to.
Unscheduled connections use the remainder of network bandwidth after scheduled connections are allocated.