1.2
Typical Mode of Operation of a CPU
Mode of operation of a CPU
The following modes of operation are possible in a CPU:
Cyclic processing
This is the main part of all activities in the CPU. As the name already
says, the same operations are repeated in an endless cycle.
Cyclic processing can be divided into three main phases, as follows:
Phase
Sequence
1
All the input modules assigned to the
CPU are scanned by the system
program and the values read in are
stored in the process image of the
inputs (PII).
2
The values contained in the PII are
processed by the user program and the
values to be output are entered in the
process image of the outputs (PIQ).
3
The values contained in the process
image of the outputs are output by the
system program to the output modules
assigned to the CPU.
Cyclic processing
Interrupt-driven processing
Time-controlled processing
1.
2.
3.
Read in process image
of the inputs
Output process image
of the outputs
&
&
= 1
I 1.5
I 1.6
I 1.4
I 1.3
Q 3.1
Evaluate input signals,
set output signals
Input I 1.3
Input I 1.4
Input I 1.5
Output Q 3.1
Output Q 2.0
Output Q 4.7
CPU
Process
Typical Mode of Operation of a CPU
CPU 948 Programming Guide
C79000-G8576-C848-04
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Summary of Contents for CPU 948
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Page 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
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Page 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Page 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Page 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...