1 Basic Principles of PLC Ladder Diagram omitted), from left to right horizontally, one row after another from up to down. See bellows for the frequently seen incorrect diagrams: DVP-PLC Application Manual 1-14 OR operation upward is not allowed. Reverse flow “Reverse flow” exists in the signal circuit from the beginning of input to output. The up-right corner should output first. Combining or editing should be done from the up-left to the bottom-right. The dotted-lined area should be moved up. Parallel operation with empty device is not allowed. Empty device cannot do operations with other devices. No device in the middle block. Devices and blocks in series should be horizontally aligned.
Label P0 should be in the first row of a complete network. Blocks connected in series should be aligned with the upmost horizontal line.