Rockwell Automation Publication 2080-UM002N-EN-E - November 2022 127
Chapter 7 Program Execution in Micro800
Example of Five Nested UDFBs
• Structured Text (ST) is much more efficient and easier to use than Ladder Logic, when
used for equations. If you are used to using the
RSLogix 500® CPT Compute instruction, a
great alternative is to use ST combined with either UDF or UDFB.
As an example, for an Astronomical Clock Calculation, Structured Text uses 40% less
Instructions.
Display_Output LD:
Memory Usage (Code) : 3148 steps
Memory Usage (Data) : 3456 bytes
Display_Output ST:
Memory Usage (Code) : 1824 steps
Memory Usage (Data) : 3456 bytes
• You may encounter an Insufficient Reserved Memory error while downloading and
compiling a program over a certain size. One workaround is to use arrays, especially if
there are many variables.
UDFB1
UDFB2
UDFB3
UDFB4
UDFB5
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