Multiplexing is the property of combining one or more signals and transmitting on a single channel. This is achieved by the device multiplexer.
A multiplexer is the most frequently used combinational circuits and important building block in many in digital systems. These are mostly used to form a selected path between multiple sources and a single destination. A basic multiplexer has various data input lines and a single output line. These are found in many digital system applications such as data selection and data routing, logic function generators, digital counters with multiplexed displays, telephone network, communication systems, waveform generators, etc.
In this article we are going to discuss about types of multiplexers and its design.Multiplexers
The multiplexer or MUX is a digital switch, also called as data selector. It is a combinational circuit with more than one input line, one output line and more than one select line. It allows the binary information from several input lines or sources and depending on the set of select linesparticular input lineis routed onto a single output line. The basic idea of multiplexing is shown in figure below in which data from several sources are routed to the single output line when the enable switch is ON.
The below figure shows the block diagram of a multiplexer consisting of n input lines, m selection lines and one output line. If there are m selection lines, then the number of possible input lines is 2m. For example, if one of the 4 input lines has to be selected, then two select lines are required. Similarly, to select one of 8 input lines, three select lines are required. Generally the number of data inputs to a multiplexer is a power of two such as 2, 4, 8, 16, etc.
Some of the mostly used multiplexers include 2-to-1, 4-to-1, 8-to-1 and to-1 multiplexers. These multiplexers are available in IC forms with different input and select line configurations. Depends on the select signal, the output is connected to either of the inputs.
Since there are two input signals only two ways are possible to connect the inputs to the outputs, so one select is needed to do these operations. If the select line is low, then the output will be switched to D0 input, whereas if select line is high, then the output will be switched to D1 input.
The figure below shows the block diagram of a 2-to-1 multiplexer which connects two 1-bit inputs to a common destination. The truth table of the 2-to-1 multiplexer is shown below. Depending on the selector switching the inputs are produced at outputsi. From the above output expression, the logic circuit of 2-to-1 multiplexer can be implemented using logic gates as shown in figure. Thus, the output generated by the OR gate is equal to D0.
Therefore, the output of the OR gate is D1. Thus, the above given Boolean expression is satisfied by this circuit.Carrie ingalls now
In some cases, two or more multiplexers are fabricated on a single IC because simple logic gates can implement the multiplexer. Generally four 2 line to 1 line multiplexers are fabricated in a single IC as shown in figure below.
The selection line controls the input lines to the output in all four multiplexers. The control input E enables and disables all the multiplexers, i. The select lines S1 and S2 select one of the four input lines to connect the output line.
The particular input combination on select lines selects one of input D0 through D3 to the output. The figure below shows the block diagram of a 4-to-1 multiplexer in which the multiplexer decodes the input through select line. The truth table of a 4-to-1 multiplexer is shown below in which four input combinations 00, 10, 01 and 11 on the select lines respectively switches the inputs D0, D2, D1 and D3 to the output.
To get the total data output from the multiplexer, all these product terms are to be summed and then the final Boolean expression of this multiplexer is given as. From the above expression of the output, a 4-to-1 multiplexer can be implemented by using basic logic gates. In this circuit, each data input line is connected as input to an AND gate and two select lines are connected as other two inputs to it.The action or operation of a demultiplexer is opposite to that of the multiplexer.
As inverse to the MUXdemux is a one-to-many circuit.Gx430t parts manual
With the use of a demultiplexerthe binary data can be bypassed to one of its many output data lines. Demultiplexers are mainly used in Boolean function generators and decoder circuits.
Also, the facility of cascading two or more IC circuits helps to generate multiple output demultiplexers.
Digital Circuits - De-Multiplexers
Let us get a brief idea of demultiplexers and its types. The process of getting information from one input and transmitting the same over one of many outputs is called demultiplexing. A demultiplexer is a combinational logic circuit that receives the information on a single input and transmits the same information over one of 2n possible output lines.
The bit combinations of the select lines control the selection of specific output line to be connected to the input at given instant.Sockeye salmon recipe
The below figure illustrates the basic idea of demultiplexerin which the switching of the input to any one of the four outputs is possible at a given instant. Demultiplexers are also called as data distributors, since they transmit the same data which is received at the input to different destinations. Thus, a demultiplexer is a 1-to-N device where as the multiplexer is an N-to-1 device. It consists of 1 input line, n output lines and m select lines.
For example, a 1-to-4 demultiplexer requires 2 22 select lines to control the 4 output lines. There are several types of demultiplexers based on the output configurations such asand A 1-to-2 demultiplexer consists of one input line, two output lines and one select line.
The signal on the select line helps to switch the input to one of the two outputs. The figure below shows the block diagram of a 1-to-2 demultiplexer with additional enable input. In the figure, there are only two possible ways to connect the input to output lines, thus only one select signal is enough to do the demultiplexing operation.
When the select input is low, then the input will be passed to Y0 and if the select input is high then the input will be passed to Y1. The truth table of a 1-to-2 demultiplexer is shown below in which the input is routed to Y0 and Y1 depends on the value of select input S.
In the table output Y1 is active when the combination of select line and input line are active high, i.One of these data inputs will be connected to the output based on the values of selection lines. So, each combination will select only one data input.
Multiplexer(MUX) and Multiplexing
Multiplexer is also called as Mux. The block diagram of 4x1 Multiplexer is shown in the following figure. One of these 4 inputs will be connected to the output based on the combination of inputs present at these two selection lines. Truth table of 4x1 Multiplexer is shown below. The circuit diagram of 4x1 multiplexer is shown in the following figure. We can easily understand the operation of the above circuit. Similarly, you can implement 8x1 Multiplexer and 16x1 multiplexer by following the same procedure.
Now, let us implement the following two higher-order Multiplexers using lower-order Multiplexers. In this section, let us implement 8x1 Multiplexer using 4x1 Multiplexers and 2x1 Multiplexer. We know that 4x1 Multiplexer has 4 data inputs, 2 selection lines and one output. Whereas, 8x1 Multiplexer has 8 data inputs, 3 selection lines and one output. So, we require two 4x1 Multiplexers in first stage in order to get the 8 data inputs.
Since, each 4x1 Multiplexer produces one output, we require a 2x1 Multiplexer in second stage by considering the outputs of first stage as inputs and to produce the final output. The Truth table of 8x1 Multiplexer is shown below. We can implement 8x1 Multiplexer using lower order Multiplexers easily by considering the above Truth table. The block diagram of 8x1 Multiplexer is shown in the following figure. The outputs of first stage 4x1 Multiplexers are applied as inputs of 2x1 Multiplexer that is present in second stage.
The other selection line, s 2 is applied to 2x1 Multiplexer.Reer warsame aadan
Therefore, the overall combination of two 4x1 Multiplexers and one 2x1 Multiplexer performs as one 8x1 Multiplexer. In this section, let us implement 16x1 Multiplexer using 8x1 Multiplexers and 2x1 Multiplexer. We know that 8x1 Multiplexer has 8 data inputs, 3 selection lines and one output. Whereas, 16x1 Multiplexer has 16 data inputs, 4 selection lines and one output. So, we require two 8x1 Multiplexers in first stage in order to get the 16 data inputs. Since, each 8x1 Multiplexer produces one output, we require a 2x1 Multiplexer in second stage by considering the outputs of first stage as inputs and to produce the final output.
Let the 16x1 Multiplexer has sixteen data inputs I 15 to I 0four selection lines s 3 to s 0 and one output Y. The Truth table of 16x1 Multiplexer is shown below.
We can implement 16x1 Multiplexer using lower order Multiplexers easily by considering the above Truth table. The block diagram of 16x1 Multiplexer is shown in the following figure. The outputs of first stage 8x1 Multiplexers are applied as inputs of 2x1 Multiplexer that is present in second stage.In electronicsa multiplexer or mux ; spelled sometimes as multiplexoralso known as a data selectoris a device that selects between several analog or digital input signals and forwards the selected input to a single output line.
A multiplexer makes it possible for several input signals to share one device or resource, for example, one analog-to-digital converter or one communications transmission mediuminstead of having one device per input signal. Multiplexers can also be used to implement Boolean functions of multiple variables. Conversely, a demultiplexer or demux is a device taking a single input and selecting signals of the output of the compatible muxwhich is connected to the single input, and a shared selection line.
A multiplexer is often used with a complementary demultiplexer on the receiving end. An electronic multiplexer can be considered as a multiple-input, single-output switch, and a demultiplexer as a single-input, multiple-output switch.
One use for multiplexers is economizing connections over a single channel, by connecting the multiplexer's single output to the demultiplexer's single input.
The image to the right demonstrates this benefit. At the receiving end of the data link a complementary demultiplexer is usually required to break the single data stream back down into the original streams. In some cases, the far end system may have functionality greater than a simple demultiplexer; and while the demultiplexing still occurs technically, it may never be implemented discretely. This would be the case when, for instance, a multiplexer serves a number of IP network users; and then feeds directly into a routerwhich immediately reads the content of the entire link into its routing processor; and then does the demultiplexing in memory from where it will be converted directly into IP sections.
Often, a multiplexer and demultiplexer are combined together into a single piece of equipment, which is simply referred to as a multiplexer. Both circuit elements are needed at both ends of a transmission link because most communications systems transmit in both directions. In analog circuit design, a multiplexer is a special type of analog switch that connects one signal selected from several inputs to a single output. In digital circuit design, the selector wires are of digital value.
For example, 9 to 16 inputs would require no fewer than 4 selector pins and 17 to 32 inputs would require no fewer than 5 selector pins. The binary value expressed on these selector pins determines the selected input pin. While this is mathematically correct, a direct physical implementation would be prone to race conditions that require additional gates to suppress.
Other common sizes are 4-to-1, 8-to-1, and to Since digital logic uses binary values, powers of 2 are used 4, 8, 16 to maximally control a number of inputs for the given number of selector inputs.
The following 4-to-1 multiplexer is constructed from 3-state buffers and AND gates the AND gates are acting as the decoder :.
Larger Multiplexers can be constructed by using smaller multiplexers by chaining them together. For example, an 8-to-1 multiplexer can be made with two 4-to-1 and one 2-to-1 multiplexers.IC Necessity of multiplexers:. Types of MUX:. It has eight data inputs D0 to D7, three select inputs S0 to S2, an enable input and one output.
Fig: MUX using gates. Ex: Implement the following Boolean function using multiplexer. Fig: Design Table. Fig: Logic Diagram. Thus we have implement four input Boolean function using multiplexer of IC You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email.
The n: 1 multiplexer can be used to realize a m variable function. Multiplexer improves the reliability of the digital system because it reduces the number of external wired connections.
Share this: Twitter Facebook. Like this: Like Loading Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in:.Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. The basis: See it this way: You need a combinational logic with 16 input pins, 4 select lines and one output.
In a mux, you have 4 input pins, two select lines and one output. So, at the least you have to use 4 MUX, to obtain 16 input lines. But you'd then have a logic with 4 output pins. We can use another MUX, to multiplex only one of those 4 outputs at a time. Hence, this would be your final design. There might be other designs methods too, but this is the most common. It utilizes the traditional method; drawing a truth table and then analytically deciding the design.
But, to obtain the same for a MUX you'll need to make a lot of modifications.
Like if you draw the truth table and analyze compare it with the above MUX designyou'll require two enable pins for each MUX, each with different options. As the size of the MUX increases, it'll become too complex to design using this model. Hence, the first approach is utilized; the one with a MUX at the end.
There may be other designs, but this is my approach. Sign up to join this community.Tolterodine drug action
The best answers are voted up and rise to the top. Asked 4 years, 5 months ago. Active 2 years, 4 months ago. Viewed 80k times. Improve this question. Debakar Roy Debakar Roy 3 1 1 gold badge 1 1 silver badge 2 2 bronze badges. Also, if you provide a schematic or drawings to your question it will improve your explanation a lot!
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MULTIPLEXER IC 74151
Improve this answer. Check the edited answer. Anyway thank you for the explanation part. I think I get it now. See the given image to verify the logical circuit It is designed by "Krishna.De-Multiplexer is a combinational circuit that performs the reverse operation of Multiplexer. The input will be connected to one of these outputs based on the values of selection lines. So, each combination can select only one output.
De-Multiplexer is also called as De-Mux.Gli open source
The block diagram of 1x4 De-Multiplexer is shown in the following figure. The Truth table of 1x4 De-Multiplexer is shown below. From the above Truth table, we can directly write the Boolean functions for each output as. The circuit diagram of 1x4 De-Multiplexer is shown in the following figure. We can easily understand the operation of the above circuit. Similarly, you can implement 1x8 De-Multiplexer and 1x16 De-Multiplexer by following the same procedure. Now, let us implement the following two higher-order De-Multiplexers using lower-order De-Multiplexers.
We know that 1x4 De-Multiplexer has single input, two selection lines and four outputs.
Whereas, 1x8 De-Multiplexer has single input, three selection lines and eight outputs. So, we require two 1x4 De-Multiplexers in second stage in order to get the final eight outputs. Since, the number of inputs in second stage is two, we require 1x2 DeMultiplexer in first stage so that the outputs of first stage will be the inputs of second stage. Input of this 1x2 De-Multiplexer will be the overall input of 1x8 De-Multiplexer. The Truth table of 1x8 De-Multiplexer is shown below.
We can implement 1x8 De-Multiplexer using lower order Multiplexers easily by considering the above Truth table. The block diagram of 1x8 De-Multiplexer is shown in the following figure. The other selection line, s 2 is applied to 1x2 De-Multiplexer.
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