Siemens CPU 948, Руководство по программированию

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Special feature with cyclic
functions on both PGs If the interrupting function blocks the CPU 948 ("status" in a block
that is not executed) the interrupted function is also blocked. It can
only be resumed when the interrupting function is terminated.
When working simultaneously with two PGs, the following sequence
results:
P G 1 i n f o r m s t h e CP U
o f t h e va r i a b l e s
t o b e o u t p u t .
PG 1 r equests the
c u r r e n t d a t a .
( P G si g n a l s : s t a t u s
p r o c e s s i n g a c t i v e )
PG 1 r equests the
c u r r e n t d a t a .
PG 1 r equests the
c u r r e n t d a t a .
P G 1 m u s t wa i t u n t i l
t h e CP U i s f r e e .
P G 2 m u s t wa i t u n t i l
t h e CP U i s f r e e .
Job sent by PG 2 i s p r o cessed
(PG signals: status processing active
( P G si g n a l s : s t a t e m e n t
n o t p r o c e s s e d )
P G 2 se n d s a n e w j o b
( e . g . " S t a t u s P B 9 " ) .
PG 2 j ob com p l e te
PG 1 r eceives new data
P G 2 a b o r t s t h e STAT US fu n c t i o n ;
T h e CP U p r o c e s s e s th e a b o r t r e q u e s
CPU 9 4 8 User o n PG 1 User o n PG 2
Fig. 11-9 Sequence when a function blocks the CPU 948
Parallel Operation of Two Serial PG Interfaces
CPU 948 Programming Guide
C79000-G8576-C848-04
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