-.
--
-
1.3
Principle of operation
1
The control functions of the
105R
are
determined by a program. This is stored
in a memory and is processed by the
microcomputer.
Program memory
The program can be produced on the
105R
by means of the programmer. The grogram
is loaded into the internal program
memory where it can be retained for
3
days* even the event of a power failure.
For long-term storage, the program can be
transferred to external plug-in memory
submodules. When the
105R
PC
is switched
.i
on, the contents of the submodule are
55
-
105R
programrnabie
automatically copied into the internal pro-
gram memory, where they can then be pro-
cessed. Programs can thus be easily inter-
changed.
I
_
-
Fig.
4
Block diagram of the
105R
programmable controller
Program processing
The program of the
105R
PC
is stored in
the program memory and scanned one pro-
gram element
at
a time. When the last ele-
ment in the program memory has been pro-
cessed, the processor starts again with
the first element. This repetitive pro-
cessing is referred to as cyclic program
scanning.
Before each program scan, all the inputs are
read in and stored in a process input image
(11,
which is part of the internal memory.
During the scan
(21,
access is made to this
input image only.
If
outputs (coils) are
latched or unlatched during program pro-
cessing, the statuses of these coils are
first assigned to the process output image
(3).
Once the last program element has
been processed, the output image is trans-
ferred to the actual outputs or coils.
The scan time of the
105R
is automatically
monitored. Before returning to
(11,
a
cheek is made as to whether program pro-
cessing has taken place correctly. In the
event of an error, the monitor disables all
outputs after
a
maximum of
0.3
S
and sets
the
PC
to the 'STOP' state.
*see also
5.3
Technical Specification of
CPU
Fig.
6
Principle of operation of the
105R
programmable control ler
1.3