FBD elements
An FBD program consists of separate elements that are linked by means of a binary signal flow. Most program elements must be supplied with tags.
A FBD network is programmed from left to right.
For example, the following figure shows elements of an FBD network:
1) Binary function
2) Standard box
3) Complex box
Binary functions
You can use binary functions to query binary operands and to combine their signal states. The following operations are examples of binary functions: "AND operation", "OR operation" and "EXCLUSIVE OR operation".
Standard boxes:
You can use standard boxes to control binary operands, perform RLO edge detection or execute jump functions in the program. Standard boxes generally have only one single input.
Complex boxes
Complex boxes represent program elements with complex functions. The empty box is an exception. You can use the empty box as a placeholder in which you can select the required instruction.
The following types of boxes are available to you in an FBD program:
-
Complex boxes without EN/ENO mechanism:
A box is executed independently of the signal state at the box inputs. The error status of the processing cannot be queried. -
Complex boxes with EN/ENO mechanism:
A box is only executed if the enable input "EN" has the signal state "1". If the box is processed correctly, the "ENO" enable output has signal state "1". If an error occurs during processing, the "ENO" output is reset.
If the EN enable input is not interconnected, the box is always executed.
Calls of code block are also shown in the network as complex boxes with EN/ENO mechanism.
See also