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4.4
RUN Mode
Execution of the user program The user program in OB 1 is executed cyclically and additional
Timers, counters, process
image
BASP
IPC flags
CYCLE
PROCESS INTERRUPTS/
INTERRUPTS
TIMED INTERRUPTS
CPU 948 Programming Guide
C79000-G8576-C848-04
When the CPU has executed a START-UP (and only then) it changes
to the RUN mode. This mode is characterized by the following
features:
interrupt-driven program sections can be nested in it.
All the timers and counters started in the program continue to run, the
process image is updated cyclically.
The BASP signal (disable command output) is switched inactive. This
enables all the digital outputs.
The IPC flags (if programmed in DB 1) are updated cyclically.
In the RUN mode, the following program execution levels exist:
The user program in OB 1 is processed cyclically.
The execution of the user program is interrupt-driven (4 interrupt
levels or 1 process interrupt level with 8 sub-levels).
The user program is processed time-controlled (9 cyclic timed
interrupts, 1 delayed interrupt, 1 clock-controlled interrupt).
The execution levels differ from each other as follows:
• • they are triggered by different events
• • there are one or more organization blocks serving as user
interfaces for each level of program execution.
All the processing levels in a CPU 948 can be programmed
simultaneously. The levels are called by the system program
according to the events that occur and the preset priority (refer to
Section 4.2).
RUN Mode
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