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RUN Mode
Delayed interrupt
Resolution
User interface
OB 6
Interruptions
Special features
4 - 34
With the delayed interrupt of the CPU 948, small time intervals with a
resolution of 1 ms can be set. Once the selected time has elapsed, the
system program calls OB 6 once.
The delayed interrupt is generated by calling the special function
organization block OB 153 (refer to Section 6.14). As soon as the
delay time assigned with OB 153 has elapsed, the system program
interrupts the current program execution and calls OB 6 (program
execution level TIMED INTERRUPTS). Following this, program
execution is resumed at the point at which it was interrupted.
The use of the delayed interrupt is, however, only possible when
"process interrupts via IB 0 = off" is set in the data block DX 0.
OB 6 is called as the user interface for a delayed interrupt. In OB 6, you
write a STEP 5 program to be executed in this situation. If OB 6 is not
loaded, program execution is not interrupted.
With the default setting, the TIMED INTERRUPTS level has the
highest priority of the basic levels (can be modified by changing the
parameter assignment in DX 0).
In timed-controlled program execution, the servicing of the delayed
interrupt has highest priority.
Owing to the distribution of priorities, the processing of the delayed
interrupt cannot be interrupted by any other user program.
• • A delayed interrupt is only processed in the RUN mode. Delayed
interrupts owing in the STOP mode, during power down or
START-UP are discarded.
• • A generated delayed alarm (= OB 153 call was processed) is not
retained in the transition to the STOP mode and during POWER
OFF.
CPU 948 Programming Guide
C79000-G8576-C848-04
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