System and operating states of the CPU 410
7.3 Self-test
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC
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RAM/PIQ comparison error
If the self-test detects a RAM/PIQ comparison error, the fault-tolerant system exits redundant
operating state and the standby CPU switches to ERROR SEARCH operating state (default
setting). The cause of the error is written to the diagnostics buffer.
The response to a recurring RAM/PIQ comparison error depends on whether the error recurs
in the first self-test cycle after troubleshooting or not until later.
Table 7- 4
Response to a recurring comparison error
Comparison error recurs ...
Reaction
in the first self-test cycle after troubleshooting
Fault-tolerant system switches to stand-alone
operation.
Standby CPU switches to ERROR SEARCH and
then remains in STOP.
after two or more self-test cycles after trouble-
shooting
Fault-tolerant system switches to stand-alone
operation.
Standby CPU switches to ERROR SEARCH.
Checksum errors
When a checksum error occurs for the first time since the last POWER ON without battery
backup, the system reacts as follows:
Table 7- 5
Reaction to checksum errors
Time of detection
System response
During the startup test after
POWER ON
The faulty CPU switches to DEFECTIVE state.
Fault-tolerant system remains in stand-alone operation.
In the cyclic self-test
(STOP or solo operation)
The error is corrected. The CPU remains in STOP operating state or
in solo operation.
In the cyclic self-test
(redundant system state)
The error is corrected. The faulty CPU switches to ERROR-SEARCH
operating state.
Fault-tolerant system switches to stand-alone operation.
In the
ERROR-SEARCH operating
state
The faulty CPU switches to DEFECTIVE state.
The cause of the error is written to the diagnostics buffer.
In an F-system, the F-program is already signaled at the first occurrence of a checksum error
in STOP operating state or in stand-alone operation that the self-test has detected an error.