1 Basic Principles of PLC Ladder Diagram MPS and MPP instruction can be omitted when the multiple outputs in the same horizontal line do not need to operate with other input devices. X0 Y1 Ladder diagram complied into instruction MPS Y0 AND X0 OUT Y1 MPP OUT Y0 Y0 Ladder diagram complied into instruction OUT Y0 Y1 X0 AND X0 OUT Y1 Correct the circuit of reverse flow In the following two examples, the diagram in the left hand side is the ladder diagram we desire. However, the illegal “reverse flow” in it is incorrect according to our definition on the ladder diagram. We modify the diagram into the diagram in the right hand side.
Example 1 X0 X1 X2 X0 X1 X2 X3 X4 X5 X3 X4 X5 X10 X6 X7 X10 LOOP1 X6 X7 X5 reverse flow X10 LOOP1 DVP-PLC Application Manual 1-16