Rockwell Automation Logix5000 Logix5000 Controllers Quick Start User Manual
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Publication 1756-QS001E-EN-P - October 2009
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Organize a Project Chapter 2
As you create user-defined data types, follow these guidelines.
Follow these steps to create a user-defined data type.
1. Right-click Data Types and choose New Data Type.
2. Type a name for the data type (not the name of a tag that will use the data type).
Guideline
Details
Consider the pass-through of descriptions.
.
Data that represents an I/O device requires
additional programming.
If you include members that represent I/O devices, you must use logic to copy the data
between the members in the user-defined data type and the corresponding I/O tags.
If you include an array as a member, limit
the array to a single dimension.
Multi-dimension arrays are not permitted in a user-defined data type.
When you use the BOOL, SINT, or INT data
types, place members that use the same
data type in sequence:
Logix5000 controllers allocate memory in 4-byte chunks. If you sequence smaller data
types together, the controller packs as many as it can fit into a 4-byte chunk.
More Efficient
BOOL
BOOL
BOOL
DINT
DINT
Less Efficient
BOOL
DINT
BOOL
DINT
BOOL