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S5-115U Manual
2.5.3
RUN Mode
After the CPU operating system has run the RESTART program, it starts cyclic program scanning
(OB1).
The input signals at the input modules are scanned cyclically and mapped to the PII; the interpro-
cessor communication input flags (see Section 12.1.1) are updated. The control program processes
this information together with the current flag, timer and counter data. The control program
comprises a succession of individual statements. The processor fetches these statements one by
one from program memory and executes them. The results are written to the process output
image (PIQ).
It is possible to react quickly to signal changes even during cyclic program scanning by:
•
Programming organization blocks to service interrupts
•
Using operations with direct I/O access (e.g. LPW, TPW)
•
Multiple programming of direct I/O scans in the control program.
2.5.4 Restart Characteristics and Cyclic Operation
The following figures give an overview of the restart characteristics of the CPUs and of cyclic
operation. They also show how the restart characteristics depend on the state of the backup
battery and they indicate the conditions for changing the operating mode.
EWA 4NEB 811 6130-02b
Technical Description
2-17
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