1 Basic Principles of PLC Ladder Diagram 3. OR (ORI) instruction: A single device connects to another single device or a block OR instruction OR instruction OR instruction The structure of ORP and ORF instructions are the same. ORP and ORF instructions only act at the rising edge or falling edge. 4. ANB instruction: A block connects to a device or another block in series ANB instruction 5. ORB instruction: A block connects to a device or another block in parallel ORB instruction If the ANB and ORB operations are with several blocks, the operation should be performed from up to down or left to right, combining into a block or network. 6. MPS, MRD, MPP instructions:
Bifurcation point of multiple outputs, for generating many and diverse outputs. MPS instruction is the start of the bifurcation point. The bifurcation point is the intersection of the horizontal line and vertical line. We will have to determine whether to give a contact memory instruction by the contact status of the same vertical line. Basically, every contact can be given a memory instruction, but considering the convenience of operating the PLC and the limitation on its capacity, some parts in the ladder diagram will be omitted during the conversion. We can determine the type of contact memory instruction by the structure of the ladder diagram.
MPS is recognized as “┬” and the instruction can be given continuously for 8 times. MRD instruction is used for reading the memory of the bifurcation point. Due to that the same vertical line is of the same logic status, in order to continue analyzing other ladder diagrams, we have to read the status of the original contact again. MRD is recognized as “├”. MPP instruction is used for reading the start status of the top bifurcation point and popping it out from the stack. Since MPP is the last item on the vertical line, the vertical line ends at this point. DVP-PLC Application Manual 1-10