Siemens SIMATIC FM 351 - Error Evaluation in the User Program

Diagnostics
11-5
FM 351 Positioning Module
C79000-G7076-C351-02
11.5 Error Evaluation in the User Program
In your user program, you can plan specific reactions to errors. The following data
are available for this purpose:
• The return values (RET_VAL) of the linked standard FCs:
This value is refreshed each time the block is called.
RET_VAL = –1 is a group indicator for a synchronous error in a job or in the
communication of the module.
• Each job has an error bit (_ERR) as a group indicator for an error in the job or
in one of its predecessors in a chain of jobs:
The error bit is set for a write job and for the subsequent jobs if a data error was
indicated by the module or if a communication error occurred.
In read jobs, the error bit is set for the job affected if a communication error
occurred.
The error bits are set again by FC ABS_CTRL after a job has been executed.
They should be reset however by the user program to allow error evaluation.
• The return signal DATA_ERR is a group indicator for an error detected by the
module in a write job. The signal is updated with the next write job.
• The return signal OT_ERR (operator error) is used as a group indicator for an
error detected by the module when a travel operation is started. The error must
be acknowledged after it has been eliminated by setting OT_ERR_A=1.
• The return signal DIAG is set when the content of the diagnostic buffer
changes. This signal can come later than the signals DATA_ERR and
OT_ERR.
• The communication error JOB_ERR contains an error code for a
communication problem between the FC and module (refer to the list of
JOB_ERR messages in Appendix C.4). The value is updated after a job has
been executed and stored by FC ABS_CTRL in the channel DB and by FC
ABS_DIAG in the diagnostic DB.
• FC ABS_DIAG for reading out the diagnostic buffer of the module. Here, you
can find out the causes of errors for synchronous and asynchronous events.
• Diagnostic interrupts for fast reaction to events in the diagnostic interrupt OB
(OB82).
Figure 11-3 shows a possible program structure with which you can react to the
return signals “Data Error” (DATA_ERR), “Operator Error” (OT_ERR) and the error
bits of the jobs (_ERR).