Editing Status: 🚧 (under construction))
Last Modification: 25.07.2021
Name
Name of the PLC Programming Pattern
Value Registry Pattern
Purpose
Name of the PLC Programming Pattern
This pattern is used to merge multiple information into a global array. This enable the forwarding of the global array and via indexing the used value out of the registry can be used.
Motivation
Reason to use this pattern
The reason to use this pattern lay in the simplicity of configurable access for index values merged from multiple code parts.
Applicability
Describes the usage context of the pattern
Merge of external and internal information into a single list to be able to select the required value by changing the index.
Structure
Describes the structure of the pattern
Actors
Introduce the involved software entities
The core entity is a Global Data Block, called GlobalValueRegistry which contains a list of UnionType that can be written by the SetValue Function or can be read by the GetValue Function.
SetValue as well as GetValue can be extended for extending error handling by missed or bad values.
Interaction
Describes the interaction between the entities
The SetValue got access to the GlobalValueRegistry and writes its Data into the given Index of the Registry.
The GetValue got also access to the GLobalValueRegistry and reads the given Index and provides it as requested Data.
Consequences
Pros and Cons of the pattern
The advantage is of this pattern is the single point of access for all configurable data flows within a PLC Program.
Disadvantage of this Pattern can also be named by higher memory footprints.
Implementation
Hints for implementation of the pattern
An examplary TIA Portal Source Code will be published soon.
Cross References
References to other related patterns
The pattern can be used in combination with the Configurable Communication to merge the external read and internal existing data to realize a single point of access object within the program. see