Rockwell Automation 1794-L34 FlexLogix Controller System User Manual - Manual (Page 115)

Publication 1794-UM001G-EN-P - January 2007
FlexLogix Back-Up on DeviceNet 115
Using Indicators to
Check Status The 1788-DNBO card’s status indicators provide useful information
(e.g. determining which controller is primary) about back-up scanner
status. Table lists the indicators to monitor when checking back-up
status.
Development and
Debugging Tips When you implement the FlexLogix Back-Up on DeviceNet solution,
we recommend you consider the following development and
debugging tips:
• Develop and debug the entire application with only the primary
controller and scanner present. When the application is totally
verified, then download the program and exact same scanlist to
the secondary controller, without the primary controller present.
Verify that the secondary is also functioning properly, and then
both primary and secondary can be added to the network at the
same time.
• No configuration parameters are entered from RSNetworx for
DeviceNet or RSLogix5000 to enable Back-up. All configuration
occurs in the user program. Almost your entire application (e.g.
except for a few ladder rungs) can be developed without
knowledge that the application will have a back-up controller
and scanner.
• Local I/O still works when this solution is used but the Local I/O
is not backed up.
• Switchover time depends on the user configurable heartbeat.
After two heartbeats are lost between primary and secondary the
switchover occurs. This time can be as little as 50ms with a
heartbeat of 16ms.
If this indicator exhibits this behavior this condition exists:
Module status (MS) Flashing red A secondary controller was not
found (or other minor fault
detected)
Back-up status (BS)
(1)
(1) The BS status indicator may not be labelled on current 1788-DNBO communication cards.
Solid green This scanner is the primary
controller.
Flashing green This scanner is a qualified
secondary controller.
Off This scanner is not configured for
back-up mode.