Allen-Bradley 2080-LC20-20QBB User Manual page 88

Chapter 6 Program Execution in Micro800
78
Example of Five Nested UDFBs
UDFB1
UDFB2
• 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, then 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.
UDFB3
UDFB4
Rockwell Automation Publication 2080-UM005E-EN-E - March 2018
UDFB5