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5.6.5
OB 26: Cycle Time
Exceeded Error (ZYK)
CPU 948 Programming Guide
C79000-G8576-C848-04
Causes of Error and Reactions of the CPU
When an addressing error occurs, the system program interrupts
further processing of the user program and calls organization block
OB 25. After running the program contained in OB 25, the program is
resumed at the next operation.
If OB 25 is not loaded, the CPU changes to the STOP mode with an
addressing error.
The STEP 5 IAE operation disables addressing error monitoring for
individual program parts or for the entire program. You can enable it
again using the RAE operation (see Section 3.5.4 and List of
Operations).
The cycle time is the time between the start of one OB 1 and the next.
It includes the entire duration of cyclic program processing including
interrupts, interrupt servicing and system program activities. The cycle
monitoring time set on the CPU can, for example, be exceeded by
incorrect programming (program loop).
Note
Hardware faults as the cause of cycle time errors are extremely
rare. Normally, the error is in the user program or the programs
and cycle monitoring time are incompatible.
When a cycle time exceeded error (ZYK) occurs, the system program
interrupts the user program and calls OB 26 if this is loaded. The
monitoring time is then restarted (triggered). If the monitoring time is
exceeded again, before OB 26 is completed, the CPU changes to the
stop mode.
If OB 26 is not loaded, the CPU changes to the STOP mode.
The cycle monitoring time is variable (10 to 2550 msec) and is
retriggerable (see above).
You can specify the cycle monitoring time individually by making an
entry in DX 0 (refer to Chapter 7) or by programming OB 31. The default
monitoring time is 200 ms.
In the cyclic program, the cycle monitoring time can be retriggered by
calling the special function OB 222.
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