Manual VIPA System 300V Chapter 3 Hardware description
HB130E - CPU - Rev. 11/50 3-3
Operating structure of a CPU
A CPU supports the following modes of operation:
• cyclic operation
• timer processing
• alarm controlled operation
• priority based processing
Cyclic processing represents the major portion of all the processes that
are executed in the CPU. Identical sequences of operations are repeated in
a never ending cycle.
Where a process requires control signals at constant intervals you can
initiate certain operations based upon a timer, e.g. not critical monitoring
functions at one-second intervals.
If a process signal requires a quick response you would allocate this signal
to an alarm controlled procedure. An alarm can activate a procedure in
your program.
The above processes are handled by the CPU in accordance with their
priority. Since a timer or an alarm event requires a quick reaction, the
CPU will interrupt the cyclic processing when these high-priority events
occur to react to the event. Cyclic processing will resume, once the
reaction has been processed. This means that cyclic processing has the
lowest priority.
The program that is present in every CPU is divided as follows:
• System routine
• User application
The system routine organizes all those functions and procedures of the
CPU that are not related to a specific control application.
This consists of all the functions that are required for the processing of a
specific control application. The operating modules provide the interfaces
to the system routines.
General
Cyclic processing
Timer processing
Alarm controlled
processing
Priority based
processing
CPU 31x
Applications
System routine
User application
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