Siemens SIMATIC S5-100U, System Manual

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S5-100U Interrupt Processing
10 Interrupt Processing, for CPU 103 Version
8MA02 and Higher
Interrupt-driven program processing starts when a signal from the CPU causes the programmable
controller to interrupt cyclic or time-controlled program scanning in order to process a specific
program. Once this program has been scanned, the CPU returns to the point of interruption in the
cyclic or time-controlled program and resumes processing at that point.
Prerequisites for Interrupt-Driven Program Processing
Interrupt-driven program processing is possible only if the following conditions are met:
• The bus unit with interrupt capability is directly adjacent to the CPU (slots 0 and 1).
• Four-channel digital input modules or comparator modules must be mounted on the bus unit to
transfer process interrupts.
- You may plug other modules in, but these modules will have no interrupt handling capability.
• The programmable controller is in the Power ON state and in the RUN operating mode.
• Interrupt processing is not disabled by an IA operation in your program. See section 8.2.8.
• OB2 has been programmed.
Figure 10-1. Possible Configuration of the Programmable Controller with Bus Units
Having Interrupt Capability
°
°
°
°
°
°
°
°
8
DI
°
°
°
°
4
DI
°
°
°
°
Slot 0 1 2 3
°
°
°
°
°
°
°
°
8
DI
4
DI
CPU
Bus unit with interrupt capability (but
acts only like a “normal” bus unit)
Interrupts are handled
only by this module
Bus unit with interrupt capability
10.1 Interrupt Processing with OB2, for CPU 103 Version 8MA02 and
Higher
For interrupt-driven processing, OB2 must have been programmed. OB2 is called up by a process
interrupt and interrupts in turn the cyclic or time-controlled program scanning. Other blocks can be
called from OB2. After the interrupt-driven program has been processed, the CPU resumes cyclic
or time-controlled program scanning.
EWA 4NEB 812 6120-02b
10-1