PLC Program to Implement 3 to 8 Line Decoder

This is a PLC Program to Implement 3 to 8 Line Decoder.

Implement 3 to 8 line decoder in PLC using Ladder Diagram programming language.

• It has three inputs I0, I1 and I2 and 8 outputs Q0 to Q7.
• These three inputs I0, I1 and I2 determines which output should be active.
• If I0 and I1 are true and I2 is false, then Q6 will be activated and all others are not.
• It does not need K-map and simplification so one step is eliminated to create Ladder Logic Diagram.
• Realize the 3 to 8 line decoder using Logic Gates.

Truth Table can be written as given below.

Inputs	   Outputs
I2 I1 I0   Q0 Q1 Q2 Q3 Q4 Q5 Q6	Q7
0  0  0	   1  0	 0  0  0  0  0	0
0  0  1	   0  1	 0  0  0  0  0	0
0  1  0	   0  0	 1  0  0  0  0	0
0  1  1	   0  0	 0  1  0  0  0	0
1  0  0	   0  0	 0  0  1  0  0	0
1  0  1	   0  0	 0  0  0  1  0	0
1  1  0	   0  0	 0  0  0  0  1	0
1  1  1	   0  0	 0  0  0  0  0	1

Realization of 3 to 8 line decoder using Logic Gates

Here is PLC program to Implement 3 to 8 Line Decoder, along with program explanation and run time test cases.

List of Inputs and Outputs
 I0=			I:1/0	(Input)
 I1=			I:1/1	(Input)
 I2=			I:1/2	(Input)
 Q0=			O:2/0	(Output)
 Q1=			O:2/1	(Output)
 Q2=			O:2/2	(Output)
 Q3=			O:2/3	(Output)
 Q4=			O:2/4	(Output)
 Q5=			O:2/5	(Output)
 Q6=			O:2/6	(Output)
 Q7=			O:2/7	(Output)

Ladder Diagram for 3 to 8 line decoder

• In all the rungs, I0 (I:1/0), I1 (I:1/1) and I2 (I:1/2) are used to determine which output from Q0 to Q7 should go ON..
• Q0 to Q7 are outputs.
• When I0 (I:1/0), I1 (I:1/1) and I2 (I:1/2) are low, output 0 O:2/0 will get activated.
• When I:1/0 and I:1/1 are low and I:1/1 is high that is when I0 and I1 are low and I2 is high, output 1 O:2/1 will get activated.
• Similarly remaining six different outputs are obtained.
• In other words, according to bit pattern of I0 I:1/0, I1 I:1/1 and I2 I:1/2, outputs from Q0 to Q7 are activated.

Inputs	   Outputs
I2 I1 I0   Q0 Q1 Q2 Q3 Q4 Q5 Q6	Q7
0  0  0	   1  0	 0  0  0  0  0	0
0  0  1	   0  1	 0  0  0  0  0	0
0  1  0	   0  0	 1  0  0  0  0	0
0  1  1	   0  0	 0  1  0  0  0	0
1  0  0	   0  0	 0  0  1  0  0	0
1  0  1	   0  0	 0  0  0  1  0	0
1  1  0	   0  0	 0  0  0  0  1	0
1  1  1	   0  0	 0  0  0  0  0	1

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