Allen-Bradley ControlNet PLC-5, Руководство пользователя

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B-4 Backup States
Primary Backup State
When a PLC-5 ControlNet backup system is in Run mode, and is
actively controlling all of the system outputs, it is in the Primary
backup state. The Primary LED is green, either blinking or solid; the
Secondary LED is off. The PLC-5 processor can go out of Primary
backup state if either the PLC-5 system is switched out of Run mode
or the partner PLC-5 becomes the Primary.
If there is a valid partner PLC-5 ControlNet backup system, and the
systems are connected on the ControlNet channel, the Qualified LED
is on. If the Qualified LED is solid yellow, the partner PLC-5 is not a
qualified secondary system, however the two systems are properly
configured to communicate with each other. If the Qualified LED is
solid green, the partner PLC-5 is a qualified secondary and could take
control of the system outputs if necessary. If the Qualified LED is off,
then there is no partner PLC-5 system communicating with this
PLC-5 system on the ControlNet channel.
When the PLC-5 is in the Primary backup state, you can no longer
force the backup system to be in the Invalid backup state through
configuration changes. All configuration changes are checked for
validity before being accepted.
Note: If a newly-entered configuration parameter is invalid, the
backup system uses the previous configuration values.
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.)