Rockwell Automation 9323-S5500D A.I. SERIES MICROLOGIX 1000 AND PLC-500 SOFTW User Manual
Page 114
Ladder Program Basics
5-9
Nested branching can be converted into non-nested branches by repeating instructions
to make parallel equivalents.
] [
] [
] [
( )
] [
] [
] [
Non-Nested Equivalent Parallel Branch
] [
] [
] [
] [
] [
( )
Nested Branch
A
B
C
F
D
E
A
B
C
F
D
C
E
Execution Time and Branch Structure Considerations
In general, non-nested branches are more efficient than nested branches. Both of the
examples shown below accomplish the same result with the same number of output
instructions; however, the non-nested branching example is evaluated approximately
1
µ
s faster than the nested branching example.
Nested Branching
( )
( )
Non-Nested Branching
( )
( )
( )
( )
You are limited to four nested branches per rung. Each nested branch, however, can
have up to 75 extended branches. Remember, you are still confined to 128 instructions
per rung, which would limit you before the branch structure would.