PLC Program to Implement 4:1 Multiplexer


This is a PLC Program to Implement 4:1 Multiplexer.

Problem Description

Implementing 4:1 multiplexer in PLC using Ladder Diagram programming language.

Problem Solution
  • There are m-data inputs, one output and n select lines, with 2m = n.
  • To select n inputs, we need m select lines such that 2m = n. Depending on the output. The selection of one of the n inputs is done by the select pins.
  • It does not need K-map and simplification so one step is eliminated to create Ladder Logic Diagram.
  • Realize the multiplexer using Logic Gates.
  • Truth Table can be written as given below.
Data	Select Inputs	Output
Inputs  S1	S0	Q
D0	0	0	D0
D1	0	1	D1
D2	1	0	D2
D3	1	1	D3

Realizing 4:1 Mux using Logic Gates

PLC Program

Here is PLC program to Implement 4:1 Multiplexer, along with program explanation and run time test cases.

List of Inputs and Outputs
 S1=		I:1/0	(Select Line Input)
 S0=		I:1/1	(Select Line Input)
 D0=		I:1/2	(Data Line Input)
 D1=		I:1/3	(Data Line Input)
 D2=		I:1/4	(Data Line Input)
 D3=		I:1/5	(Data Line Input)
 Q=		O:2/0	(Output)

Ladder Diagram to obtain Binary output

Program Description
  • In all the rungs, S1 (I:1/0) and S0 (I:1/1) are used as a selector line input as shown in Logic Circuit.
  • D0, D1, D2 and D3, I:1/2, I:1/3, I:1/4 and I:1/5 are Data Inputs respectively.
  • When S1 (I:1/0) and S0 (I:1/1) are low, output will have whatever state D0 I:1/2 holds, either 1 or 0.
  • When S1 (I:1/0) is low and S0 (I:1/1) is high, output will have whatever state D1 I:1/3 holds.
  • Similarly remaining two different inputs are performed.
  • In other words, according to bit pattern of S1 and S0, Data bits D0 to D3 are passed to output.
  • Here, instead of bits D0 to D3, any functions such as moving, jumping or moving can be performed as well depending upon the application.
Runtime Test Cases
Data    Select Inputs  Output
Inputs	S1     S0      Q
D0-0/1	0      0       D0-0/1
D1-0/1	0      1       D1-0/1
D2-0/1	1      0       D2-0/1
D3-0/1	1      1       D3-0/1

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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