Principle Of Operation - Siemens Simatic S5 Operating Instructions Manual

Principle of operation
The P U 631 i s equipped w i t h a program
memory (PU-memory) with a c a p a c i t y of 4 K
s t a t e m e n t s . The b u i l t - i n backup b a t t e r y
r e t a i n s t h e program f o r a p e r i o d of 30
minutes a f t e r t h e P U has been switched'
o f f . I n t h e on-line mode of o p e r a t i o n a
P C S5-130 may work e i t h e r w i t h i t s own
EPROM-memory o r with t h e PU-memory.
The P C ~ 5 - 1 1 0 ~ / 010 can o n l y work with
t h e PU-memory i n t h e on-line mode.
To prevent malfunctions of t h e c o n t r o l l e r
d u r i n g on-line o p e r a t i o n (PC w i t h PU-memory)
o n l y complete networks ( o r b a s i c software
modules i n t h e case of STL) may be t r a n s -
f e r r e d t o t h e PU-memory d u r i n g program i n -
p u t t i n g o r a l t e r a t i o n . T h i s i s achieved
i n t h e P U 631 with an i n t e r m e d i a t e b u f f e r
s t o r a g e .
A
network element o r statement which was
i n p u t t e d , appears i n i t i a l l y i n t h e i n p u t
f i e l d of t h e screen. A f t e r d e p r e s s i n g keys
o r
,
t h e s t a t e m e n t i s t r a n s -
f e r r e d t o t h e i n t e r m e d i a t e b u f f e r .
A f t e r a completed i n p u t o r a l t e r a t i o n of a
network, t h e c o n t e n t s of t h e i n t e r m e d i a t e .
b u f f e r must be t r a n s f e r r e d t o t h e PU-memory
by p r e s s i n g key
.
Note:
During o f f - l i n e o p e r a t i o n t h e t r a n s f e r from
t h e i n t e r m e d i a t e b u f f e r t o t h e PU-memory i s
done a u t o m a t i c a l l y a s soon a s t h e i n t e r -
mediate b u f f e r i s f u l l . Hence key
m
needs
o n l y t o be depressed a t t h e end of program
i n p u t t i n g .