Rockwell Automation 9323-PA1E USER MANUAL APS 6.0 - Manual (Page 60)

Preface
Advanced Programming Software User Manual
4–6
Parallel Logic
Another form of logical continuity is parallel (OR) logic. This means that when one
or another path of logic is true, energize the output.
Example — Parallel Inputs
a c
b
In the above example, if A or B is true, energize C.
Use branching to form parallel logic in your user program. Branches can be
established at both input and output portions of a rung. The upper limit on the
number of levels which can be programmed in a branch structure is 75. The
maximum number of simple instructions per rung is 128. (The maximum number
decreases if the rung contains instructions with many parameters, or if complex
addressing is used.)
Input Branching
Use an input branch in your application program to allow more than one
combination of input conditions to form parallel branches (OR-logic conditions). If
at least one of these parallel branches forms a true logic path, the rung logic is
enabled. If none of the parallel branches forms a true logic path, rung logic is not
enabled and the output instruction logic will not be true. Output is not energized.
Example — Parallel Input Branching
a b d
c
In the above example, either A and B, or C provides a true logical path.