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Often, complicated programs are the result of attempts to reduce the number
of times a bit is used.

Every instruction line must also have at least one condition on it to determine
the execution condition for the instruction at the right. Again, diagram A , be-
low, must be redrawn as diagram B. If an instruction must always be exe-
cuted (e.g., if an output must always be kept ON while the program is being
executed), the Always ON Flag (1813) in the SR area can be used.

Instruction

1813

Instruction

0000

LD

1813

0001

Instruction

There are, however, a few exceptions to this rule, including the INTERLOCK
CLEAR, JUMP END, 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 in-
struction lines leading to these instructions. Refer to 

for details.

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 

OR LOAD for more details and 4-6 Inputting, Modifying and Checking the
Program for further examples.

0000

0001

0207

0207

0001

0000

0207

0207

0000

LD

0000

0001

LD

0001

0002

AND

0207

0003

OR LD

---

0004

OUT

0207

0000

LD

0001

0001

AND

0207

0002

OR

0000

0003

OUT

0207