
70
Instruction
0408
Instruction
Diagram A
Diagram B
Address
Instruction
Operands
000
LD
0408
001
Instruction
There are a few exceptions to this rule, including the INTERLOCK CLEAR
and step instructions. Each of these instructions is used as the second of a
pair of instructions and is controlled by the execution condition of the first of
the pair. Conditions should not be placed on the instruction lines leading to
these instructions.
When drawing ladder diagrams, it is important to keep in mind the number of
instructions that will be required to input it. In diagram A, below, an OR LOAD
instruction will be required to combine the top and bottom instruction lines.
This can be avoided by redrawing as shown in diagram B so that no AND
LOAD or OR LOAD instructions are required. Refer to 3-7-6 AND LOAD and
OR LOAD for more details.
0000
0001
0107
0107
0001
0000
0107
0107
Diagram A
Diagram B
Address
Instruction
Operands
000
LD
0000
001
LD
0001
002
AND
0107
003
OR LD
---
004
OUT
0107
Address
Instruction
Operands
000
LD
0001
001
AND
0107
002
OR
0000
003
OUT
0107
Advanced Programming
Section 3-6