Introduction.

Workshop PG5
Program structures
Technical
stuff:
Process image
.
Unlike the PLC's from SIEMENS or Rockwell, our PLC does not
work with a so-called process image. If you work with a process image,
then the PLC reads the state of all connected inputs and outputs at the
beginning of the program cycle. Then during the cycle the PLC doesn't
read and write to the inputs and outputs anymore, but to the image. At
the end of the program cycle the PLC then writes all the results at once
from the image to the outputs. Changes at the inputs which appear during
the program cycle are not taken into consideration. If you want to write
directly to an output during the program cycle you can still do so, but
you have to configure the output consequently.
SAIA PLC’s, always read and write directly from and to the inputs &
outputs. This can be used if you want some program parts (and their
Inputs & Outputs) to be treated more often then the rest of the program.
You just have to put this part of the program into a PB and call the PB
several times during the main cycle. Another nice solution would be to
use an "Exception block" (XOB 14 or 15)
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