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1.3
The Programs in a CPU
System program
Update process image
of the inputs
Output process image
of the outputs
Manage memory
Fig. 1-1
Tasks of the system program
CPU 948 Programming Guide
C79000-G8576-C848-04
The program existing on every CPU is divided into the following:
• • the system program
and
• • the user program.
The system program organizes all the functions and sequences of the
CPU which do not involve a specific control task (refer to Fig. 1-2).
System
program
Communication with
the PG
The Programs in a CPU
Execute start-up
Call
user
processing
(inter-
faces)
Handle errors
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