Delta Electronics Programmable Logic Controller DVP-PLC - Manual (Page 14)

1 Basic Principles of PLC Ladder Diagram
DVP-PLC Application Manual 1-10
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.
MPP is recognized as “└”. Using the method
given above for the analysis cannot be wrong.
However, sometimes the compiling program will ignore
the same output status, as shown in the figure.
MPS
MRD
MPP
MPP
MPS