Toshiba T2N User Manual download pdf (Page 213)

5. Programming Language

200 PROSEC T2N

(2) SFC (Sequential Function Chart)

This is a programming language suitable for process stepping control

(sequential control). Also, it is a language which makes the flow of

control easy to see. Therefore, it is effective for program maintenance

and standardization. SFC program is composed of structure part which

shows the flow of control, action program which shows the operation of

each step and transition condition parts which enable the process to

advance. Action part and transition condition parts are produced by

ladder diagrams. SFC can be considered as an execution control

element for making a program easier to see by arranging the control

processes and conditions rather than a single programming language.

(SFC Structure)

The flow of control advances downward from the initial step and,

when it reaches the end step, it returns to the initial step. A step

corresponds to an operational process, and there is an

actionprogram corresponding to each step. The condition of

shifting from one step to the next is called ‘transition’, and there is

a transition condition corresponding to each transition. When the

immediately preceding step of a transition is in the active state

and the transition condition is ON, the state of the immediately

preceding step is changed to inactive and the next step becomes

active.

Initial step

Transition

Step

Divergence of simultaneous sequences

Divergence of sequence selection

(Transition condition)

(Action program)

End step

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Toshiba T2N User Manual Page 213