Siemens SIMATIC S7-GRAPH Manual page 12

Product Overview
The Blocks of a Sequential Control System
A sequential control system controls the process in a fixed order dependent on
certain conditions.
The complexity of the sequential control system depends on the automation task.
However, even the simplest system requires at least the three following blocks:
• A STEP 7 block (1) in which the S7-Graph FB (function block) is called. This
block can be an organization block (OB), a function (FC), or another FB.
• An S7-Graph FB (2) that describes the individual subtasks and
interdependencies of the sequential control system. These subtasks (steps) and
interdependencies (transitions) can be organized in one or more sequencers.
• An instance DB (3) that contains data and parameters of the sequential control
system. The instance DB is assigned to the S7-Graph FB and can be created
automatically by the system.
OB/FB/FC
CALL FBi,DBi
INIT_SQ:=
1-2
(1) FB i
Comments for...
S1
T1
S2
T2
S7-GRAPH for S7 300/400 Programming Sequential Control Systems
(2)
FC70/71/72
DB i
C79000-G7076-C526-01
(3)