Quick Start User Manual

Publication IASIMP-QS011B-EN-P — January 2009 103
CompactLogix Base Program Overview Appendix A
User-defined Data Types
The pre-configured Logix program uses pre-configured user-defined data types (UDT). These are
structures that organize data, status information, and commands for machine process and
equipment.
For example, this pre-configured UDT stores all the data for an axis, including speeds, accels,
decels, direction, and sequencers. A tag structure is created for each axis based on this data type.
Axis Data UDT Example
A UDT provides these advantages:
• One tag contains all of the data related to a specific aspect of your system. This keeps related
data together and easy to locate, regardless of its data type.
• Each individual piece of data (member) gets a descriptive name. This automatically creates an
initial level of documentation for your logic.
• You can use the data type to create multiple tags with the same data layout.