Siemens SIMATIC S7-400H - Checksum Errors; RAM;PAA Comparison Error; Response to a Recurring Comparison Error; Response to Checksum Errors

System and Operating Modes of the S7-400H
5-12
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
RAM/PAA comparison error
If the self-test detects a RAM/PIQ comparison error, the fault-tolerant system quits
redundant mode and the standby CPU goes into TROUBLESHOOTING mode
(default configuration). The cause of the error is entered in the diagnostics buffer.
The response to a recurring RAM/PIQ comparison error depends on whether the
error occurs in the subsequent self-test cycle or not until later.
Table 5-5 Response to a recurring comparison error
Comparison Error Occurs Again ...
Reaction
In the first self-test cycle subsequent to error
search
The standby CPU goes into
TROUBLESHOOTING mode and then into
STOP mode.
The fault-tolerant system goes into single
mode.
After two or more self-test cycles
subsequent to error search
Standby CPU goes into
TROUBLESHOOTING.
The fault-tolerant system goes into single
mode.
Checksum errors
If a checksum error occurs for the first time since the last unbuffered POWER ON,
the system responds as follows:
Table 5-6 Response to checksum errors
Detection Time
System Response
During the power-up test after
POWER ON
Faulty CPU goes into DEFECTIVE mode.
The fault-tolerant system goes into single mode.
In the cyclic self-test
(STOP or single mode)
The error is corrected. The CPU remains in STOP or in
single mode.
In the cyclic self-test
(redundant system mode)
The error is corrected. Faulty CPU goes into
TROUBLESHOOTING mode.
The fault-tolerant system goes into single mode.
In TROUBLESHOOTING mode Faulty CPU goes into DEFECTIVE mode.
The fault-tolerant system goes into single mode.
The cause of the error is entered in the diagnostics buffer.
If a checksum error reoccurs within 7 days, the faulty CPU goes into DEFECTIVE
mode and the fault-tolerant system goes into single mode.
In an F system, the F program is informed that the self-test has detected an error
the first time a checksum error occurs in STOP or single mode. The reaction of the
F program to this is described in the manual Automation Systems S7-400F and
S7-400FH.