Introduction to Industrial Automation

Figure 7.45  A group of faults cause the activation of corresponding light indications and the 

sounding of a common siren. (a) A series of pumps, (b) the corresponding PLC wiring diagram 

for the case of faults from two pumps.

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  Introduction to Industrial Automation

language program that includes the creation of the two impulses and the logic of activating the 

output devices is as follows:

A

I2.0

AN M13.1

=

M13.0

A

M13.0

S

M13.1

AN I2.0

R

M13.1

AN I2.2

AN M14.1

=

M14.0

A

M14.0

S

M14.1

A

I2.2

R

M14.1

O

M13.0

O

M14.0

S

Q0.0

AN I2.4

R

Q0.0

A

I2.0

=

Q0.2

AN I2.2

=

Q0.4

BE

O

M13.0

O

M14.0

S

Q0.0

AN I2.4

R

Q0.0

A

I2.0

=

Q0.2

AN I2.2

=

Q0.4

BE

When the number of faults is large, as explained in the previous example, the L and T instruc-

tions can be utilized for transferring data massively by simplifying the programming task (less 

number of instructions). Figure 7.47 shows the case of a series of 16 faults, expressed by an equal 

number of S

1

–S

16

 sensors that are inputs of the PLC. For each fault, it is desired to activate a 

Μ13.0

(S

1

)

Fault 

1

h

1

Μ14.0

(S

2

)

Fault 2

h

2

1 SC

duration

1 SC

duration

Figure 7.46  Creation of a one-scan cycle pulse for each fault.

PLC

Inputs

Outputs

0 V

+24 V DC

0 V

+24 V DC

I0.0

S

1

S

9

Q2.0

S

8

I0.7

I1.0

I1.7

S

16

h

1

h

8

h

9

h

16

Q2.7 Q3.0

Q3.7

Figure 7.47  Successive inputs/outputs can be faced in groups as a byte or word.

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Basic Programming Principles of PLCs 

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315

corresponding indicator light for as long as this lasts. Similarly, it is desired to activate a logical 

coil for each fault, because a portion of the logic coil memory area is transmitted as information 

via a communication network to another PLC. The corresponding required programming of the 

PLC using the L and T instructions can be performed in the form of byte or word as shown in the 

following programs:

L

IW0

T

MW100

T

QW2

BE

WORD

L

IB0

T

MB100

T

QB2

L

IB1

T

MB101

T

QB3

BE

BYT E

At this point, it is suggested that the reader write the instructions needed to handle the faults 

one by one in order to have a full understanding of the required number of instructions and the 

programming shortening that has been achieved. A prerequisite for using the L and T instructions 

at word or byte level is that both inputs and outputs must have successive addresses.