Siemens SIMATIC S7 F, Руководство пользователя

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Fail-Safe Blocks
Fail-Safe Systems
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8.15 Error Handling
Safety-Relevant Errors
If safety-relevant errors are detected in fail-safe blocks, the system function SFC
F_CTRL is called. SFC F_CTRL records the event in the Diagnostic Buffer and
requests a switch to the reserve CPU if the error only occurred on the master CPU.
The shutdown logic should be configuration for partial or full shutdown to handle
features in non-redundant systems or common cause faults on redundant systems
(both CPUs encounter a fault at the same time).
Errors in the Event of Value Range Violations
REAL data type values of Underflow (very small real numbers) and Overflow are
not considered a range violation for REAL data values. They are simply
considered very small and very large values and will be accepted, used and
generated by the fail-safe blocks without incident. If a fail-safe block generates an
invalid REAL number, the system function SFC 65097 (WRSYMSG) is called to
record the event in the Diagnostic Buffer. Once generated, invalid REAL numbers
will be accepted and used by subsequent fail-safe blocks without incident.
Remedy: check the values using, for example, F_LIM_R.
Error Information in Diagnostic Buffer
In the event of an error, error information is written into the Diagnostic Buffer. By
reading the Diagnostic Buffer you can find out:
•
The data block number of the fail-safe block that triggered the error.
•
An error code and thus the cause of the error.
The error codes and their causes are described for each of the fail-safe blocks.
Error Information at the Output RETVAL
Return values of the system functions (RET_VAL) are indicated at the output
RETVAL for the blocks for F communication between CPUs. The return values are
error codes that give you additional assistance in finding the error.
See Also
Error Information at the Outputs of the Driver Blocks
Error Information at the Output RETVAL