Siemens SIMATIC S5-100U, System Manual

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S5-100U Introduction to STEP 5
• Saving data
If a time-controlled OB uses scratchpad flags that are also used in the cyclic control program,
then these scratchpad flags must be saved in a data block during the processing of the time-
controlled OB.
Note
When processing OB13, you may not exceed the block nesting depth of 16 levels.
When processing with CPU 103 (6ES5 103-8MA03), you may not exceed the block
nesting depth of 32 levels.
• Reading out the interrupt PII
When OB13 is called, the signals of the input modules are read into the interrupt PII. The
interrupt PII can be scanned in OB13 by means of the L PY 0 to 127 or L PW 0 to 126 load
operations (load byte x or word x of the interrupt PII in ACCU 1). There is an interrupt input data
cycle prior to time-controlled program processing. The interrupt data cycle time lengthens the
response time of the cyclical program processing.
If other operands are entered, the CPU goes in the STOP mode (see section 5.2.1). This error
is indicated in ISTACK by the “NNN” error message.
• Writing to the interrupt PIQ
Data to the external I/Os can be written to the interrupt PIQ by means of transfer operations
T PY 0 to 127 or T PW 0 to 126. The “normal” PIQ is written to simultaneously. After OB13
has finished, the data that has been transferred to the interrupt PIQ is output to the peripheral
I/Os in an interrupt output data cycle (before “normal” program processing). The interrupt data
cycle time lengthens the response time of the cyclical program processing.
Note
The interrupt output data cycle is executed only if the interrupt PIQ has been written to.
7.4.5 Interrupt-Driven Program Processing, for CPU 103 Version 8MA02
and Higher
For CPU 103 version 8MA02 and higher, interrupt-driven program processing is initiated when a
signal from the process causes the CPU to interrupt the cyclic or time-controlled program
processing and execute a specific program. When this program has been scanned, the CPU returns
to the point of interruption in the cyclic or time-controlled program and resumes scanning at that
point. Chapter 10 contains detailed information about interrupt processing.
EWA 4NEB 812 6120-02b
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