Allen-Bradley PLC-2/30

Introduction to Programming
Chapter 4
49
The branch instructions allow more than one combination of input
conditions to energize an output device (Figure 4.11).
These are two branch instructions:
Branch Start
Branch End
Figure 4.11
Branching
Instructions
||
11
()
00
111 010
||
12
111
Two
Branch
Start
Instructions
A
Single
Branch End
Instruction
T
wo Possible Paths for
Logic Continuity (ORLogic)
Branch Start
This instruction begins each parallel logic branch of a rung. The Branch
Start is programmed immediately before the first instruction of each
parallel logic path.
Branch End
This instruction completes a set of parallel branches. The Branch End is
entered after the last instruction of the last branch to end a set of parallel
branches.
Branch instructions must be entered in the correct order for proper logic
function. The only limitation is that a nested branch (a branch within a
branch) cannot be programmed directly (Figure 4.12).
4.3.3
Branch Instructions
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