The FBD program consists of one or more FBD box instructions. You can assign one or more bit values as inputs to FBD box instructions without the need for touch points. The output of an instruction can be used to connect the instruction to subsequent instructions or terminate a program segment. Therefore, a single FBD instruction can provide the same functionality as a set of contacts, coils, and/or boxes in ladder logic. After all instruction parameters have been assigned or connected to other instructions, program creation is complete.

• FBD, LAD, and STL are consistent in that they are both grouped based on networks. A network can contain only one FBD instruction, or it can even be an empty network.

• There is no fixed maximum number of instructions for each network. You can view the FBD program editor window as a grid divided into cells (cells are areas where instructions can be placed, values can be specified for parameters, or line segments can be drawn). In this grid, a single network can extend up to 255 cells horizontally or 65535 cells vertically. The initial width in the horizontal direction is 8 cells, which can automatically expand with the addition of instructions.

• If the box instruction has>>output, it must provide a connection to another box or assign a value to the output parameter. But for outputs marked with "ENO", the enable output can be left blank, connected to another box, or assigned a value to the output parameter.

• You cannot directly connect the outputs of several instructions together as a horizontal line. If multiple outputs are to be connected, each output must be connected to the input parameters of an AND or OR box (producing a single output).