Rules for Creating Networks in FBD (GS 4.3)

An FBD network is composed of one or more FBD box instructions. Instead of using contacts, you can assign one or more bit values as inputs to an FBD box instruction. The output(s) of the instruction can be used to connect the instruction to a subsequent instruction, or to terminate the network. A single FBD instruction, consequently, can provide the same functionality as a set of contacts and coils and/or boxes in ladder logic. When all of the parameters of the instruction(s) have been either assigned or connected to another instruction, the network is complete.

ˇIf it is appropriate in the context of your program, you can create a network that contains only one FBD instruction.

ˇThere is no fixed maximum number of instructions per network. You can think of the FBD Program Editor window as a grid divided into cells (cells are the areas where you can place an instruction, assign a value to a parameter, or draw a line segment). Inside that grid, an individual network can extend no further than 32 cells horizontally or 32 cells vertically.

ˇIf a box instruction has >> outputs, you must provide either a connection to another box or else an assignment to the output parameters. However, in the case of >| outputs labeled ENO, the output can be left blank, connected to another box, or given an assignment.

ˇYou cannot directly tie the outputs of several instructions together into a single horizontal line. If you want to connect several outputs, you must connect each output to an input parameter of an AND box or an OR box (which results in a single output).