INITIALISATION AT THE START OF THE
PROGRAM
When a program containing an SFC chart is launched (initialised), the
program needs to know which operating phase must be activated first; i.e. which
is the step containing a status token at the time of initialisation. To set up
this step in the chart, at least one SFC function called INITIAL SFC STEP (INIT
STEP) or RESETTABLE INITIAL SFC STEP (RESET-INIT) must be used per independent
SFC chart.
An independent SFC chart describes a group of SFC functions interlinked
by token type links between the I/O (status token circulation).
- All charts which only contain one or more INITIAL SFC STEP (INIT
STEP) functions are initialised automatically; these INIT STEP functions
contain a status token which indicates the active operating phases. All other
steps belonging th the other functions do not contain any token, none off the
operating phase's tha they indicate are activated.
- This automatic initialisation also occurs when restarting after a
mains power failure. The positions of the status tokens at the time of the
power failure are lost.
- In all the charts which contain a RESET-INIT function, it is
COMPULSORY to place an ON signal on the REINITIALISATION input RIGHT AT THE
START OF THE PROGRAM and to disable the controller OUTPUTS which could take on
dangerous unwanted states; on restarting after a mains failure, the positions
of the status tokens at the time of the power failure are restored.
First example: An SFC chart has two INITIAL SFC STEP
functions

Second example: Two independent SFC charts each have one INITIAL
SFC STEP function

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