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Maintenance
204
840 USE 106 00 January 2003
Forcing a
Switchover
Through
Software
You can force a switchover using the RDE or, if you have programmed a CHS
instruction in ladder logic, a Zoom screen. The instructions are the same; however,
in the RDE you are working with the command and status registers, while in the
Zoom screen you are working with the command and status pages.
Step Action
1 Addressing the Primary controller: Check the status register or page to be sure
one unit is designated A and the other is B. Be sure that both the Primary and
the Standby controllers are in run mode and that the function keyswitch override
has been enabled.
2 In the command register or on the command page, take the Primary controller
offline.
3 If you are operating on a Modbus Plus network, the programming panel is
automatically communicating with the Primary controller. If you are operating via
the Modbus or Modbus Port directly connected to the original primary controller,
you must reconnect the programming cable to the new Primary controller and
then log in again, due to the port address swap.
Result: The status should now show that the original Primary controller is offline
and that the Standby is now functioning as the Primary unit. Refer to
Command
Register, p. 76
.
4 Check the LED displays on the Hot Standby modules to confirm that the
switchover has taken place. The Primary indicator on the original Primary unit
should be extinguished, while the Primary indicator on the original Standby unit
should be a steady green.
5 In the command register or on the command page, return the original Primary
unit to RUN mode. The status register or page and the LED display on the front
panel of the Hot Standby module should now show that unit in Standby mode.