6. Redundancy with NX3030 CPU
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PX2612 Buttons
This section describes the functions of the PX2612 buttons.
The STAND-BY button has the following functions:
ï‚· To request a switching from the Active state to the Stand-by state, useful when maintenance in
the Active CPU is needed. After the Active CPU is switched to Stand-by (and consequently the
Stand-by CPU is switched to Active), it’s possible to switched from Stand-by to Inactive using
the INACTIVE button, and then execute the programmed maintenance in the inactive state.
ï‚· To request a configuration which causes a switching from the Not-Configured to the Starting
state, typically after the failures that caused the transition to the Not-Configured state are
repaired. After the Starting state, normally the CPU is supposed to go to the Stand-by state (or
Active, if the other CPU isn’t in the Active state).
ï‚· To request a switching from the Inactive state to the Not-Configured state requesting a
configuration already. This occurs typically after the failures which caused the transition to the
Inactive state were corrected. After the Not-Configured state, the configuration must take it to the
Starting state. After the Starting state, normally the CPU is supposed to go to the Stand-by state
(or Active, if the other CPU isn’t in the Active state).
The INACTIVE button requests a switching from the Stand-by state to the Inactive state, which can
be useful to execute a programmed maintenance in the Stand-by CPU. After this maintenance, the
STAND-BY button may be used to make it go back to the Stand-by state, passing by the Not-
Configured and Starting state (see previous description of the STAND-BY button).
The TURN ON PLCx (x = B for PLCA, or x = A for PLCB) button is used to cause a reactivating in
the other CPU, in case the local CPU has switched off. As it is described in the Transition between
Redundancy States section, there are exceptional situations when a CPU switches off the other at
assuming the Active state, in order to avoid the possibility of both CPUs to assume the Active state
simultaneously.
ATTENTION:
For a button to be considered, it must be pressed for at least 1 second. Furthermore, during this
second, only this button must be pressed (the other 2 buttons must be released).
ATTENTION:
There are alternative ways to generate the same effects of the STAND-BY, INACTIVE and TURN
ON PLCx buttons. Commands generated by the local CPU or the remote CPU can be used, as
described, preliminary, in the Diagnostics, Commands and User Data Structure section. A more
detailed description of these commands can be found in the Redundancy Commands section.
PX2612 LEDs
The PX2612 LEDs are used to inform the redundancy state, as shown on the following Table 6-2:
Active (switching off the other CPU)
Active (recent and switching off the
other CPU)
Table 6-2. PX2612 LEDs
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General