5 . Sequential Function Chart

S10

S

S20

S

Y0

SET S20

Y1

Y2

S10

S

S20

S

Y0

Y1

SET S20

Y2

2.As indicated in the below diagram, make sure to connect RET instruction directly after the step point rather than the NO or NC contact.

S20 X1

S

S20 X1

S

S0

RET

S0

RET

5.4Points to Note for Designing a Step Ladder Program

1.The first step in the SFC is called the “initial step", S0 ~ S9. Use the initial step as the start of a sequence and ends with RET instruction.

2.If no STL instruction is in use, step point S can be used as a general-purpose auxiliary relay..

3.When STL instruction is in use, the No. of step S cannot be repeated.

4.Types of sequences:

Single sequence: Only one simple sequence without alternative divergence, alternative convergence, simultaneous divergence or simultaneous convergence in the program. Complicated single sequence: Only one sequence with alternative divergence, alternative convergence, simultaneous divergence and simultaneous convergence in the program. Multiple sequences: More than one sequence in a program, maximum 10 sequences, S0 ~ S9.

5.Sequence jump: Multiple sequences are allowed to be written into the step ladder diagram.

z There are two sequences, S0 and S1. PLC writes in

S0 ~ S30 first and S1 ~ S43 next..

OUT

S0

OUT

S1

z

Users can assign a step in the sequence to jump to

 

any step in another sequence.

z

When the condition below S21 is fulfilled, the sequence

 

will jump to step S42 in sequence S1, which is called

 

“sequence jump.”

S21

S30

OUT

S41

S42

S43

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Image 631
Delta DVP-ES2/EX2/SS2/SA2/SX2/SE manual Points to Note for Designing a Step Ladder Program, S41 S42 S43