Siemens CPU 948 User Manual

4.4.1
Cyclic Program Execution With programmable controllers, cyclic program execution (program
execution level CYCLE) is the main mode.
Triggering If the CPU has completed the start-up program without errors, it then
begins cyclic program execution.
Principle The principle of cyclic program execution (system activities):
From start-up
Trigger cycle monitoring time
Update IPC input flags
Supply process image of the
inputs (PII)
Call cyclic user program (OB1)
User program
other program
execution levels
including nesting in of
Output process image of the
outputs (PIQ)
Update IPC output flags
System activities e.g.
loading or deleting blocks
compressing blocks . . .
Fig. 4-6 Cyclic program execution
RUN Mode
CPU 948 Programming Guide
4 - 30 C79000-G8576-C848-04

Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English