Toshiba T2N - Manual (Page 222)

5. Programming Language
User's manual 209
5.3
SFC
SFC is the abbreviation of Sequential Function Chart. This is a
programming language suitable for process stepping control (sequential
control). In the T2N, an SFC is applied in which the following functions
are added to general SFC.
* Jump ... Moves the active state to an arbitrary step when a jump
condition is satisfied.
* Step with waiting time... Even if the transition condition is satisfied,
step transition is not carried out until a set
time has elapsed. (wait step)
* Step with alam ... When transition to the following step is not
carried out even if the set time has
elapsed, the designated alarm device
becomes ON.(Alam step)
SFC can be used in the main program. Here the overall composition of
SFC, the composition factors of SFC and notes on program creation are
described.
An SFC program is composed of SFC structure, action program parts
and transition condition units.
An SFC structure regulates the flow of the control operation and has
steps and transitions as its basic elements. A step is expressed by one
box, as shown above. Each step has its own step number. Also,
corresponding execution programs are annexed 1 to 1 to steps.
Steps have the two states of active and inactive. When a step is active,
the power rail of the corresponding execution program will be in the live
state (power rail ON). When a step is inactive, the power rail of the
corresponding action program will be in in the cut off state (power rail OFF).
On the other hand, a transition is located between step and step, and
expresses the conditions for transition of the active state from the step
immediately before (upper step) to the following step (lower step).
Corresponding transition conditions are annexed 1 to 1 to transitions.
For instance, in the diagram above, when step 120 is active, the
execution program power rail corresponding to step 120 becomes ON.
In this state, when device A becomes ON, the transition conditions are
satisfied, and step 120 becomes inactive and step 121 becomes active.
In accompaniment to this, theaction program power rail corresponding to
step 120 becomes OFF (executed as power rail OFF), and the action
program power rail corresponding to step 121 becomes ON.
(SFC structure)
Step
(Action program unit)
(Transition condition unit)
Step number
Transition
Step