Connecting Instructions in LAD
LAD offers horizontal and vertical lines to help connect instruction references in series and in parallel arrangements. By connecting the power flow output of one instruction to the power flow input of another, you create the logic in your program. LAD provides some horizontal connections automatically, and can even expand boxes vertically to align power flows.
Contacts and boxes can be connected in a logical series. Coils can be used to terminate such a series. Horizontals are sometimes needed to connect the power flows of a series of instructions. Horizontals are used here to connect the Add Real and Multiply Real boxes.
When a parallel connection is required, verticals are needed. A vertical can extend up and/or down from the cell of origin. In the configuration above, the Move Byte instructions are in parallel.
Automatic Power Flow Connection
When an element is placed in a network, the ladder editor automatically connects the power flow input of the element to any power flow indicator to the left. In the network above, LAD extends power flow to the Read Real-Time Clock instruction.
In this example, the Table Find box occupies many rows of the network. In order for the second power flow input of the Count Up box to be connected to the output of the Compare Double Integer contact, the box was automatically expanded. Power flow was extended to connect the aligned power flow inputs of the new box to the power flow indicators in the network.
When a box is placed in a network, and the box contains two or more power flow inputs, the ladder editor will automatically align the power flow inputs with the power flow indicators of the network.