Siemens CPU 948 Programming Manual page 17

Simatic s5 s5-155u
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User program
Tasks
CPU 948 Programming Guide
C79000-G8576-C848-04
The user program contains all the functions required for processing a
specific control task. In general terms, these functions can be
assigned to the interface provided by the system program for the
various types of processing, as follows:
Type of processing
Cold and warm restart
Cyclic processing
Time-controlled
processing
Interrupt-driven processing Special, fast reactions to certain process
Error reaction
The Programs in a CPU
Task
To provide the conditions under which
the other processing functions can start
from a defined status following a cold or
warm restart of the control system (e.g.
assigning specific values to signals).
Constantly repeated signal processing
(e.g. logic operations on binary signals,
reading in and analyzing analog values,
specifying binary signals for output,
outputting analog values).
Special, time-dependent processing with
the following time conditions:
- faster than the average cycle,
- at a time interval greater than the
average cycle time,
- at a specified point in time.
signals.
Handling problems within the normal
sequence of the program.
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