6. Redundancy with NX3030 CPU
289
Failure in Connected MODBUS Server
The time to detect the fault in a remote MODBUS Server depends on the time-out settings configured
on each MODBUS Client. When a fault is detected in all Servers, the bAllDevicesCommFailure
diagnostic (see Modbus Diagnostics used at Redundancy section used in) changes its state to TRUE.
When this happens, the switchover will happen 3 seconds after this transition.
OPC Communication Use with Redundant Projects
The OPC protocol can be configured to communicate with redundant clusters over SCADA systems.
When this option is selected in the creation of a redundant project, the Symbol Configuration object
is added to the project. In this object are set system variables that will be sent to the SCADA system.
This communication option is enabled in the CPU of the Ethernet ports NX3030. For further
information related to the configuration of an OPC communication with redundant projects, refer to
the Configuration with the PLC on the OPC Server with Connection Redundancy section of this
Manual.
Redundant CPU States
In a redundant system, a CPU (PLCA or PLCB) may assume the following states:
Active
Stand-by
Inactive
Not-Configured
Starting
ATTENTION:
Frequently this manual will use the designation “Non-Active” for each state different from Active, in
other words, to design any one from the other 4 states (Stand-by, Inactive, Not-Configured and
Starting). An Active CPU is the one that is in Active state and a Non-Active CPU is the one that
isn’t in Active state.
In the following sections these five states are briefly described. Further details regarding the
redundant CPU states are described in the Transition between Redundancy States section, when the
state machine and the transition causes are also described.
Not-Configured State
This is the initial redundancy state. The CPU is found in this redundancy state:
By convention, while the CPU is OFF
Before starting the MainTask
Before the Starting state is switched
In case there’s a restart through a command as reset warm, reset cold or reset origin
In case the MainTask is being executed in the Not-Configured state, the following tasks are executed:
The PROFIBUS masters are disabled
The cyclic synchronization services are executed (see Cyclic Synchronization Services through
NETA and NETB section), if the condition for its execution are true
The sporadic synchronization services can also be executed (see Sporadic Synchronization
Services through NETA and NETB section)
The CPU will be blocked in the Not-Configured state if the other CPU is in Active state, and this
CPU project is different from the Active CPU project (except if the project automatic
synchronization is disabled – see Project Synchronization Disabling). In case this situation doesn’t
occur, a transition from the Not-Configured state for the Starting state happens as soon as a
configuration request arrives.
To Next Page
Loading...
General