Technical data

•• 9 TIME INTERRUPTS: the user program is processed at
fixed intervals specified by the
system.
•• CONTROLLER time-driven processing of a preset
INTERRUPT: number of closed loop controllers.
•• DELAY The user program is processed
INTERRUPT once after a preset delay
time has elapsed.
•• PROCESS process interrupt-driven user
INTERRUPT: program execution.
The processing levels differ from each other in the following aspects:
•• they are triggered by different events
•• the user interface for each program processing level is a different
organization block or function block.
You can program all basic processing levels at the same time in a
CPU 928B. The levels are called by the system program according to
the default priority (see Section 4.2).
4.5.1
Cyclic Program Execution
Most functions of a programmable controller involve cyclic program
execution
(CYCLE program processing level). This cycle is known
as a "free cycle", i.e. after reaching the end of the program, the next
cycle is executed immediately (see Fig. 4-6).
Triggering If the CPU completes the restart program without errors, it begins
cyclic program execution.
RUN Mode
CPU 928B Programming Guide
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