Manual 26166V1 MicroNet Simplex & MicroNet Plus
Woodward 16
Figure 2-5. Redundant Inputs
This process can be expanded for triplicated inputs. With triplicated inputs, redundant inputs are available if
an input fails. It is also possible to determine which input is not valid when using triplicated inputs.
2.1.6—Redundant Outputs
Redundancy can be added to the outputs as well. Additional external relays can be used to prevent a
faulted output from affecting the external device. For discrete outputs, this would require four relays for each
output. For the actuator outputs, a dual coil actuator can be used. The dual coils will allow one coil to
operate the actuator in the event of a failure.
The value of redundancy is dependent on the ability of the application to detect the failure. For analog and
actuator outputs, current and/or voltage read back is provided. For discrete outputs, fault detection requires
sensing the relay contact state.
2.2—MicroNet Plus Redundant Operation
To use the MicroNet Plus for redundant operation, a CPU must be in the first VME slot (slot A1) and a CPU
must be in the last VME slot (slot A14). In the GAP application select the MICRONET14 or MICRONET8
chassis type and place a MicroNet Plus compatible CPU module in both A1 and A14 / A8 slots.
Start-up
Load and start the application on each CPU using AppManager.
If the CPUs are started within 20 seconds of each other they will boot in the “Redundant” mode.
If the CPUs are not started within 20 seconds of each other the first CPU started will become the
master and the second CPU will have to re-sync to the running CPU.
If the applications are not the same and both CPUs are started together, CPU1 (located in slot A1) will
be the SYSCON and the backup CPU will be failed.
Normal Operation (Redundant)
Normally the CPUs will be powered up together and will start running the application within the 20
second window.
The first CPU to start running the application will remove the WATCHDOG (as indicated by the red
LED on the CPU) and become the SYSCON (as indicated by the green LED on the CPU).
When the second CPU starts running the application the SYSCON control will go to CPU1 (located in
slot A1).
Both CPUs will establish communication and CPU2 will temporarily become SYSCON (as indicated by
the green LED on the CPU) to do a diagnostic test to ensure it can drive the VME bus.
This diagnostic test will switch the SYSCON between both CPU1 and CPU2 three times before
proceeding.
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