Delta DVP-ES2/EX2/SS2/SA2/SX2/SE manual Actions of Step Points, STL Transition

5 . Sequential Function Chart

Actions of Step Points:

STL program is composed of many step points, and each step point represents a single task in the STL control process. To perform a sequential control result, every step point needs to do 3 actions.

1.Drive output coils

2.Designate the transition condition

3.Designate which step will take over the control from the current step

Example:

S10	Y0			S10	Y0
S				S
	SET	Y1			SET	Y1
	X0		When X0 = ON,		X0
	SET	S20			SET	S20
			S20 = ON,
S20			S10 = OFF.	S20
S	Y20			S	Y20
	X1				X1
	SET	S30			SET	S30

Explanation:

When S10 = ON, Y0 and Y1 will be ON. When X0 = ON, S20 will be ON and Y20 will be ON. When S10 = OFF, Y0 will be OFF but Y1 will still be ON (SET instruction is applied on Y1, so Y1 will be ON and latched.)

STL Transition:

When step point Sn is ON, its following output circuit will be activated. When Sn = OFF, its following output circuit will be OFF. The interval between the activation of the step point and its following output circuit is one scan cycle.

Repeated Usage of Output Coil:

4.Output coils of the same number could be used in different step points.

5.See the diagram opposite. There can be the same output device (Y0) among different steps (sequences). Y0 remains ON when S10 transfers to S20.

6.Y0 will be OFF due to the transition from S10 to S20. However when S20 is ON, Y0 will be ON again. Therefore in this case, Y0 remains ON when S10 transfers to S20.

7.For general ladder diagrams, repeated usages

S10

S

S20

S

Y0

SET Y1

X0

SET S20

Y0

X1

SET S30

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