Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 85)

Publication 1785-UM024B-EN-P - January 2003
Backup States B-5
Lonely Primary Backup State
The Primary LED is solid green if there is at least one good scheduled
connection on the ControlNet channel. If there are no good scheduled
connections on the ControlNet channel the Primary LED blinks green.
This is referred to as the Lonely Primary backup state. Since there are
no valid scheduled connections on the ControlNet channel, this PLC-5
is not controlling the system outputs on the ControlNet channel.
A system could go into Lonely Primary backup state, for example,
when the ControlNet cable is disconnected.
When in Lonely Primary backup state, the PLC-5 waits 10 seconds
after the first connection is established before actively controlling the
system outputs on the ControlNet channel. This is so that if an existing
partner PLC-5 is controlling the system outputs on the ControlNet
channel, the PLC-5 system in Lonely Primary backup state does not
take control of the system outputs from the partner. If, during the
10-second wait, the PLC-5 in Lonely Primary backup state establishes
communication with the partner PLC-5 and notices that the other
PLC-5 is a primary, the PLC-5 in the Lonely Primary backup state
major faults. (Refer to chapter 4 for description of specific major fault
codes.)
Secondary Backup State
When a PLC-5 ControlNet backup system is in Run mode, and is not
actively controlling the system outputs, it is in the Secondary backup
state. The Secondary LED is solid yellow, the Primary LED is off, and
the Qualified LED is solid green. The PLC-5 can go out of Secondary
backup state if either the PLC-5 system goes out of Run mode, or the
partner PLC-5 system is no longer the primary. If the partner PLC-5 is
no longer the primary, the PLC-5 in the Secondary backup state
becomes the primary and assumes control of the system outputs.
When the PLC-5 is in the Secondary backup state, you cannot make
any backup configuration changes to that PLC-5 system. All backup
configuration changes must be made to the primary system and those
changes are immediately passed on to the secondary system.