Siemens CPU 948 User Manual

11.4.3
Sequence in Certain
Operating Situations
Parallel operation with
short-running functions
If you work with PGs on both interfaces simultaneously, both PGs
want to execute their functions independently of each other. As long
as they stagger the jobs they send to the CPU, the jobs will be
processed in the order in which they arrive.
The situation may, however, arise that the CPU 948 either receives
two jobs simultaneously or receives a job from the second PG while a
job from the first PG is still active.
Since simultaneous processing is not possible, the jobs are processed
one after the other; the second job is, however, delayed by such a short
time that it is hardly noticeable for the user.
When jobs are sent simultaneously, the sequence is as follows:
From this sequence, you can see that both PGs can operate
independently from each other, but that the one nevertheless affects
the other.
It is possible that both PGs process the same block simultaneously or
that a block currently being processed by one PG is deleted by the
other PG.
With this configuration, you must always take into account the way in
which input at one PG affects the other PG.
Input at keyboard of PG 1
Interpretation of input 1 in PG 1
Job1transferredtotheCPU
Job 1 processed in the CPU
Resultsofjob1transferredtoPG1
Results of job 1 interpreted
Results of job 1 displayed
on PG 1
CPU 948
User on PG 1
Job1transferredtotheCPU
Job 2 processed in the CPU
Resultsofjob2transferredtoPG2
Results of job 2 interpreted at PG 2
Results of job 2 displayed on PG 2
Input at keyboard of PG 2
Interpretation of input 2 in PG 2
*
*
*
*
User on PG 2
Here PG 2 must wait
until the CPU has
processed job 1.
Fig. 11-6 Handling simultaneous jobs
Parallel Operation of Two Serial PG Interfaces
CPU 948 Programming Guide
C79000-G8576-C848-04
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Siemens CPU 948 Specifications

General

Brand	Siemens
Model	CPU 948
Category	Controller
Language	English