Diagnostic Interrupt, Module Failure Processing (Ob 82, Ob 86); Response To Nck Failure - Siemens SINUMERIK 828D Function Manual

P3: Basic PLC Program for SINUMERIK 840D sl
13.8 Structure and functions of the basic program
13.8.5

Diagnostic interrupt, module failure processing (OB 82, OB 86)

General
A module diagnosis or module failure on an I/O module triggers OB 82 / OB 86. These blocks are supplied by the
basic program. The basic program block FC5 is called in these OBs. This is wired by default to trigger a PLC stop
in the event of an error being detected.
A PLC Stop
• If the cause of the error is removed, a PLC stop will not be triggered.
• does not occur in case of the Profibus-MCPs specified as the FB 1 parameters.
The response can be changed by modifying the FC5 parameter setting.
PROFIBUS Diagnosis
The slaves of both the PROFIBUS connections MPI/DP or DP1 are registered by the basic program as group
message in the form of a ready signal in the interface signal
DB10 DBX92.0 (MPI/DP Bus Slaves OK) and
DB10 DBX92.1 (DP1 Bus Slaves OK)
The group message is derived from the LED status of the respective PROFIBUS (System state list SZL 0x174).
If an error or a failure of a slave is detected, the alarm 400551 or 400552 is also reported. The alarm is
automatically deleted when the error is removed. Detailed information about the error or the failure will be
displayed in the alarm messages as exact cause of error in a future HMI software version in the diagnostics. No
FC 125, FB 125 is necessary for this diagnostic display, because the information is called directly from the HMI
via the corresponding SZL functions of the PLC operating system via the communication channels to the PLC.
This saves the relatively large block in the PLC and reduces also the PLC cycle time. Since the FB 125 works
under interrupt disable during its processing, OBs with a higher priority can be executed more quickly.
Note
Till the HMI software version with the diagnostic display for the PROFIBUS becomes
available, it is recommended to use FC 125 for PROFIBUS diagnostics. This block has
relatively less cycle time and the slave states can be updated via the DB 10 interface signal
mentioned earlier by activating the FC 125 block.
13.8.6

Response to NCK failure

General
During cyclic operation, the PLC basic program continuously monitors NCK availability by polling the sign­of­life
character. If the NCK is no longer reacting, the NCK PLC interface is initialized, and the NCK CPU ready signal in
the area of the signals from NC (DB 10.DBX 104.7) is reset. Furthermore, the signals sent from the NCK to the
PLC and vice versa are set to an initial state.
The PLC itself remains active so that it can continue to control machine functions. However, it remains the
responsibility of the user program to set the machine to a safe state.
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions