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11.4.3
Sequence in Certain
Operating Situations
Parallel operation with
short-running functions
User on PG 1
Input at keyboard of PG 1
Interpretation of input 1 in PG 1
Job 1 transferred to the CPU
Job 1 processed in the CPU
Results of job 1 transferred to PG 1
Results of job 1 interpreted
Results of job 1 displayed
on PG 1
Fig. 11-6
Handling simultaneous jobs
CPU 948 Programming Guide
C79000-G8576-C848-04
Parallel Operation of Two Serial PG Interfaces
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:
CPU 948
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.
User on PG 2
Input at keyboard of PG 2
Interpretation of input 2 in PG 2
*
Here PG 2 must wait
*
until the CPU has
*
processed job 1.
*
Job 1 transferred to the CPU
Job 2 processed in the CPU
Results of job 2 transferred to PG 2
Results of job 2 interpreted at PG 2
Results of job 2 displayed on PG 2
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