The automobile designer doesn’t need to be an expert or be concerned with how the copper in the engine is mined.

The analogy is an automobile engine which has a starter, which has an armature, which is wound with copper wire, which is extruded from copper, which is mined throughout the world. In this way, upper levels of the design are not cluttered with confusing and unnecessary detail that is important at the lower levels of the design. The building block technique is easier to design and understand because it enables and encourages the practice of maintaining a consistent level of detail at each level of the hierarchy. Small building blocks have many advantages over the traditional large flat designs, including being easier to: Hierarchical design is the practice of creating a design from building blocks, which are built from simpler building block, which are built from simpler building blocks and so on.

Allows information to flow upstream and downstream (to further reduce the unnecessary detail).Keeps the block size small so that the overall flow of information can be viewed on one page.They remove unnecessary detail from this level of the design hierarchy so that the forest isn’t lost in the trees (to paraphrase the saying).If there are a significant number of connections between blocks, the lines can be consolidated into pins that are declared as a data structure type as shown in Figure 2.įigure 2: Structure pins enhance readability of diagrams by reducing unnecessary detail and clutter. If the functionality begins to become complex, it should be split into smaller, more manageable sub-blocks as described in hierarchical designs below. When there is a combination of state-less and state-based functionality, use a combination of CFC and SFC.īecause connectivity is represented with lines between the function blocks, it is easy to understand the flow of information and how the information is modified along its path.

CFC block programming is excellent when the outputs are strictly a function of the current inputs (in other words, when there are no state variables such as Boolean feedback, set/reset coils, or flags). Block-based programming with CFCīlock-based designs consist of assemblies of pre-defined functionality which are wired together to carryout Boolean logic, mathematical calculations, or a combination of the two as shown in Figure 1. Figure 1: An example of a block-based programming design is show in Codesys continuous function chart language programing from Codesys GmbH.

Structured text tutorial