# 4 to 1 multiplexer using structural verilog code FaceBook Likes. Powered by Blogger. About Me Unknown View my complete profile. Popular Posts. Share to Twitter Share to Facebook. Newer Post Older Post Home. Search Here. Total Pageviews. Design of 8 : 3 Parity Encoder using conditional o Design of 8 nibble queue using Behavior Modeling S Design of 8 nibble Stack using Behavior Modeling S Design of Integer Oathbreaker paladin 5e spells using Behavior Modeling Design of Frequency Divider Divide by 10 using B Design of Frequency Divider Divide by 8 using Be Design of Frequency Divider Divide by 4 using Be Design of Frequency Divider Divide by 2 using Be Design of 4 Angular datatable server side pagination Comparator using Behavior Modeling Small Description about Behavior Modeling Style in Design of 4 to 1 Multiplexer using case statements Design of 2 to 4 Decoder using if-else statements Design of 4 to 2 Encoder using if -else statements Design of 4 to 1 Multiplexer using if -else statem Design of 4 Bit Adder cum Subtractor using xor Gat Design of 4 Bit Adder cum Subtractor using Structu Design of 4 Bit Subtractor using Structural Modeli Design of 2 to 1 Multiplexer using Gate Level ModeA multiplexer or mux in short, is a digital element that transfers data from one of the N inputs to the output based on the select signal.

The case shown below is when N equals 4. For example, a 4 bit multiplexer would have N inputs each of 4 bits where each input can be transferred to the output by the use of a select signal.

## Design of 4×2 Multiplexer using 2×1 mux in Verilog

Each value on the select line will allow one of the inputs to be sent to output pin out. A 4x1 multiplexer can be implemented in multiple ways and here you'll see two of the most common ways:.

The multiplexer will select either abcor d based on the select signal sel using the assign statement. Click to try this example in a simulator! Note that the signal out is declared as a reg type because it is used in a procedural block like always.

The multiplexer will select either abcor d based on the select signal sel using the case statement. Both types of multiplexer models get synthesized into the same hardware as shown in the image below.

You consent to our cookies if you continue to use our website. To know more about cookies, see our privacy policy. I accept cookies from this site. What is a mux or multiplexer? Using assign statement Using case statement Hardware Schematic Testbench.

### Verilog code for 8:1 Multiplexer (MUX) – All modeling styles

Prev Article. Next Article.Now before jumping to the coding section, a brief description of each modeling style has been presented before you. As the name suggests, this style of modeling will include primitive gates that are predefined in Verilog.

The prerequisite for this style is knowing the basic logic diagram of the digital circuit that you wish to code. We can orally solve for the expression of the output that comes out to be:. For the gate level, we will first declare the module for 2: 1 MUX, followed by the input-output signals.

The order of mentioning output and input variables is crucial here, the output variable is written first in the bracket, then the input ones. Next comes the declaration of input, output, and intermediate signals. You might have noticed that other modeling styles include the declaration of variables along-with their respective data- types. Next comes the instantiation part for gates. This is the design abstraction, which shows the internal circuitry involved.

It is the hardware implementation of a system. For coding in the dataflow style, we only need to know about the logical expression of the circuit. The equation for mux is:. To start with this, first, you need to declare the module. This operator?

### VHDL 4 to 1 Mux (Multiplexer)

Final code:. The hardware schematic for a multiplexer in dataflow level modeling is shown below. You will notice that this schematic is different from that of the gate-level.

It involves the symbol of a multiplexer rather than showing up the logic gates involved, unlike gate-level modeling. This level describes the behavior of a digital system.Forums New posts Unanswered threads Search forums.

Hi, I am trying to write verilog code for mux using rtl but I am finding difficulty in the test bench code. Last edited by a moderator: Apr 4, Re: Verilog Hardware description language lines sucky antiquated usage of pre-Verilog module port declaration syntax Use Verilog syntax it's much cleaner and requires no repeating of the post names in two places. Use whitespace in your code from now on it's free or nearly so and it makes code much easier to read, instead of a packed messes of characters you have to really look at to determine if something starts or ends.

Also learn to indent code, haven't you ever written C and been told to indent stuff? You should also learn to proof read you code before posting these are ALL easy to spot mistakes.

You're probably using some crappy "editor" like windows notepad sucks or wordpad sucks even more. Need Verilog mux testbench Hi guys, Can anyone provide me the test bench for mux using structural or gate level modelling in verilog? Last edited by a moderator: Apr 6, Re: Need Verilog mux testbench pakha said:.

Hi guys, Can anyone provide me the test bench for mux using structural or gate level modelling in verilog? Re: Need Verilog mux testbench Hi, I am trying to design 2 stage 16 bit pipelined adder using 8 bit adder and i have worked very very hard on this and I sat down and finally wrote the code.A multiplexer is a data selector which selects a particular input data line and produce that in the output section. It is implemented using combinational circuits and is very commonly used in digital systems. Sending data over multiplexing reduces the cost of transmission lines, and saves bandwidth. You can find a detailed explanation and schematic representation for multiplexers over here. This article will deal with the modeling styles for an multiplexer. The gate-level modeling is virtually the lowest abstract level of modeling. This style of modeling will include primitive gates that are predefined in Verilog HDL.

The designer should know the basic logic circuit and the logic gates that are employed in that circuit for a particular system. There is another abstraction layer below gate-level: switch level modeling, which deals with the transistor technologies. First of all, we need to mention the timescale directive for the compiler. This will control the time unit, which measures the delays and simulation time, and time precision specifies how delays are rounded off for the simulation.

The following code will be simulated in nanoseconds, as mentioned in the time unit 1 nsand the precision is up to 1 picosecond.

We can declare the data lines and select lines as vector nets also. In some of the complex circuits, we need intermediate signals, and they are declared as wire s.

If there exist more than two same gates, we can concatenate the expression into one single statement. The RTL schematic shows the hardware layout of a circuit.

The following window will open up when you click on the RTL analysis section. This modeling represents the flow of the data through the combinational circuit.

Instead, we should know the final output expression of the given circuit. This is the highest abstraction layer of all. It emphasizes the behavior of the digital circuit. In most cases, implementing the truth table will describe the behavior with no failure. One can find numerous ways to implement the truth table, whether it is a nested if-else statement or case statement.

In the structural style of modeling, we only define the physical structure of the circuit. This modeling is somewhat similar to gate-level modeling. The difference lies in the use of predefined gates. In structural style, we will declare and define the operation of each of the logic gate and then use that expression for implementing the rest of the gates, by the concept of module instantiation. Decide which logical gates you want to implement the circuit with.

The next thing to be done is the instantiation of modules. The testbench is a set of lines that are used to test and simulate the design code for a given system. It tests the design for a variety of possible inputs.

Follow up this post for step-by-step instruction to write a testbench. The above simulation result is the same for each of the abstraction layers, truly satisfying the truth table. Chanchal is a zestful undergrad pursuing her B.Post a comment. VHDL Programming. Verilog HDL. Find US on FaceBook. Email Subscribe. Naresh Singh Dobal. Powered by Blogger. About Me naresh. Live Traffic Feeds Live Traffic Stats. Popular Posts. With the help of modeling styl Share to Twitter Share to Facebook.

Newer Post Older Post Home. Search Here. Total Pageviews. Design of 8 : 3 Priority Encoder using if - else Design of 8 to 3 Priority Encoder using When Else Design of 8 nibble Queue using Behavior Modeling S Design of 8 - nibble stack using Behavior Modeling VHDL C Design of Frequency Divider Divide by 10 using B Design of Frequency Divider Divide by 8 using Be Design of Frequency Divider Divide by 4 using Be Design of Frequency Divider Module Divide by 2 u Design of Integer counter using Behavior Modeling Design of a Simple numbers based Grading System us Design of 4 to 1 Multiplexer using if-else stateme Design of 4 Bit Adder cum Subtractor using StructuA multiplexer is a data selector device that selects one input from several input lines, depending upon the enabled, select lines, and yields one single output.

A multiplexer of 2 n inputs has n select linesare used to select which input line to send to the output. These devices are used extensively in the areas where the multiple data can be transferred over a single line like in the communication systems and bus architecture hardware. Visit this post for a crystal clear explanation to multiplexers. The gate-level abstraction is the lowest level of modeling. The gate-level modeling style uses the built-in basic logic gates predefined in Verilog. We only need to know the logic diagram of the system since the only requirement is to know the layout of the particular logic gates. The port-list will contain the output variable first in gate-level modeling. This is because the built-in logic gates are designed such that the output is written first, followed by the other input variables or signals. The intermediate signals are declared as wires.

Note that the intermediate signals are those that are not involved in the port list. Example: signals that are emerging from the NOT gate. Time for us to write for the logic gates. Separate the list for a particular gate by appropriate brackets, if there exists more than one same logic gate. Here s0bar and s1bar are the output to the first and second NOT gate respectively and s0 and s1 are the input to the first and second NOT gate.

This hardware schematic is the RTL design of the circuit. Notice the resemblance between the logic circuit of MUX and this picture. It is clear that the gate-level modeling will give the exact involved hardware in the circuit of the system.

The dataflow modeling represents the flow of the data. It is described through the data flow through the combinational circuits rather than the logic gates used. It is necessary to know the logical expression of the circuit to make a dataflow model. The equation for MUX is:. Start with the module and input-output declaration. Using the assign statement to express the logical expression of the circuit. A ternary operator? This operator works similar to that of C programming language.

This shows that if s1 is high, the s0? Further, if s0 is high, d OR b will get transferred to the out variable, depending on the s1 select line, else c OR a will be the output. Thus, the final code for the multiplexer using data-flow modeling is given below. The figure consists of two individual multiplexers, connected by the two select lines s0 and s1.

The behavioral style, as the name suggests, describes the behavior of a circuit.

Designing 4:1 MUX using Verilog Software

It is the highest abstraction layer in the Verilog modeling of digital systems. The truth table of the MUX has six input variables, out of which two are select lines, and one is the output signal. The input data lines a, b, c, d are selected depending on the values of the select lines. ##### Zulujin 