Delta DVP-ES2 - Manual (Page 631)

5 . S e q u e n t i a l F u n c t i o n C h a r t
SET
Y0
S10
S
S20
S Y2
S20
Y1 SET
Y0
S10
S
S20
S Y2
S20
Y1
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.
S0
S20
S
RET
X1
S0
S20
S
RET
X1
5.4 Points 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..
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.”
S0
S21
S30
OUT
OUT
S1
S41
S43
OUT
S42
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