Programming the Structure of the Sequencer
S7-GRAPH for S7-300/400 Programming Sequential Control Systems
C79000-G7076-C526-01
6-5
Simultaneous Branch Close
Branch Stop
Insert Sequencer
You program the structure of the sequencer at the overview or single page display
level.
Tip: The overview level shows you the structure of the sequencer in the most
compact form.
6.5
Step-Transition Pair and Initial Step
Step /Transition Pair
As default, the S7-Graph FB already contains one step-transition pair to which you
can append further step-transition pairs.
Steps and transitions can only be inserted in pairs in a sequencer.
When you insert steps and transitions, they are automatically assigned a number.
To ensure a better overview, you can renumber steps and transitions within a
certain range later so that the numbering is consecutive.
Initial Step
The initial step is the step in a sequencer that becomes active without previously
querying conditions when an S7-Graph FB is first called. The initial step is not
necessarily the first step in a sequencer.
When a sequencer is run through cyclically, this step (just like every other step)
only becomes active when the conditions of the previous transition are satisfied.
The sequencer is initialized by the FB parameter INIT_SQ = 1. In other words the
sequencer starts with the initial step.
