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S5-115U Manual
•
OB6 cannot itself be interrupted.
•
OB6 can interrupt the cyclic or time-controlled program but not a running interrupt program
(OB2 to 5)! If the clock prompt expires while an interrupt OB is being processed, the OB6 call is
delayed as a result.
•
The OB6 call can also be delayed in the following circumstances:
-
If integral FBs are used
-
If the integral clock has been initialized
-
If PG/OP functions are pending
-
If SINEC L1 is connected
-
If a computer link or ASCII driver have been activated
or
-
If time-controlled OBs have been programmed.
Table 9-1 in Chapter 9 (Interrupt Processing) contains the time by which the OB6 call is
delayed.
7.4.5
Handling Programming Errors and PLC Malfunctions
It is possible to determine the response of the CPU to errors and malfunctions using error response
OBs.
The operation which triggers the timeout, substitution or transfer errors can be replaced by
calling the relevant error response OB. Appropriate responses to errors can be programmed in
these OBs. If only "BE" is programmed there, no response follows, i.e. the PLC does not go to
STOP. If no relevant OB exists, the CPU jumps to the STOP mode.
OB19
Response when an unloaded block is called
In OB19, you can program the response of the CPU when an unloaded block is called.
Example:
The CPU is to go to STOP when an unloaded block is called:
OB19 STL
:STP
:BE
If OB19 has not been programmed, the control program continues execution (no re-
sponse) immediately after the jump statement (the destination of the jump does not
exist!)
OB23
Response to timeout in the case of direct I/O access
The following operations can result in timeout: L PB; LPW; T PB; T PW; LIR; TIR; TNB.
The timeout (QVZ) error occurs if a module fails to acknowledge within 160 µs of being
accessed. The cause may be a program error, a defect in the module or the removal of
the module during the RUN mode. The operating system stores the absolute module
address at which the QVZ occurred in system data word 103 (EACE
OB23 does not exist, the CPU goes to STOP with QVZ.
EWA 4NEB 811 6130-02b
Explanation
STOP statement
Introduction to STEP 5
) and calls OB23. If
H
7-23
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