<8. Detailed Description>
8.1.2 Checking Operation Specification of Analog/Digital
Output
Compare the operation specification of each module with the requirement
specification to ensure that there is no problem.
SEE ALSO
For details of operation specification of analog/digital output, see:
Section A1.6, “I/O Modules” of IM “STARDOM FCN/FCJ Guide”
Check the requirement specification regarding output fallback upon CPU failure and
reverse output, and perform setup accordingly using Resource Configurator.
● Checking Output Fallback Operation
- Detection of CPU failure
The CPU module and I/O modules of the FCN-500 or FCN-RTU perform
diagnostic communication at the time of each task for Input and/or Output. When
an error is generated in the CPU module of the FCN-500 or FCN-RTU, this
diagnostic communication cannot proceed. If an I/O module operating normally
detects an interruption in diagnostic communication exceeding the designated
line access loss time, it assumes a CPU failure.
Line access loss time: 4 seconds (system-defined and not user-configurable)
SEE ALSO
For details on the specification of the output fallback operation, see Section C3.2, “Operation When an
I/O Module Malfunctions” of IM “STARDOM FCN/FCJ Guide.”
As CPU failure detection is implemented through diagnostic communication, a false
CPU failure may be detected by an I/O module under the following
circumstances even though the CPU is running normally:
- Long execution time of control task
If the scan cycle is set to 4 seconds or longer, or if control processing
exceeds 4 seconds for whatever reason, the output module will detect a CPU
failure.
- E2 bus failure
If an extension unit is used and a failure occurs in the E2 bus cable or E2 bus
interface module, I/O beyond the point of failure will detect a CPU failure.
- Power supply failure of extension unit (using E2 bus)
In a system that uses extension unit, if the power supply module of extension
unit "n" fails, the E2 bus interface module of extension unit "n" stops running,
I/O on extension unit "n" and downstraem unit will detect a CPU failure.
- SB bus failure
If an extension unit is used and a failure occurs in the SB bus cable or SB
bus repeat module, I/O beyond the point of failure will detect a CPU failure.
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