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. 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.
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. 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.
From the above truth table, the logic diagram of this demultiplexer can be designed by using two AND gates and one NOT gate as shown in below figure. Then, the data from the input flows to the output line Y1.
A 1-to-4 demultiplexer has a single input Dtwo selection lines S1 and S0 and four outputs Y0 to Y3. The input data goes to any one of the four outputs at a given time for a particular combination of select lines. This demultiplexer is also called as a 2-to-4 demultiplexer which means that two select lines and 4 output lines. The truth table of this type of demultiplexer is given below. From the above Boolean expressions, a 1-to-4 demultiplexer can be implemented by using four 3-input AND gates and two NOT gates as shown in figure below.
The two selection lines enable the particular gate at a time. So depends on the combination of select inputs, input data is passed through the selected gate to the associated output.Track My Order. Frequently Asked Questions.
International Shipping Info. Send Email. Mon-Fri, 9am to 12pm and 1pm to 5pm U. Mountain Time:. Chat With Us. So you've read through the LogicBlocks introductory tutorial or the kit's included documentationand are ready for some experiments!?
Time to put those LogicBlocks to use! Each experiment includes a schematics, and matching LogicBlock layouts for the circuit under test. There are also smatterings of truth tablesstate diagramsand boolean equations throughout each experiment. And they're all capped off with challenges, questions, and sub-experiments. To get the most out of each experiment, make sure you check out the sub-experiments!
Nothing too fancy here. Remember, this is what the AND gate's truth table should look like:. While we're here, let's discuss the other two fundamental gates. Can you lay out the fundamental, two-input OR gate with LogicBlocks? It'll require a similar set of blocks to the AND:. Now that you've got a handle of the three, fundamental logic gates, let's add some inputs!8:1 MUX (block diagram and Truth Table )
Onto the next experiment Sometimes you need to AND more than two inputs together. In fact, 3- and 4-input AND gates are just as common as the dual-input variety. Start by building the 2-input AND block from the last experiment, but plug the output of that into the input of another AND. With three total inputs, how many different input combinations can you make? This number grows exponentially at 2 nwhere n is the number of inputs.
So, a 4-input AND gate has 16 possible combinations, 5 inputs would be 32 outputs, and so on. NAND gates are very popular in the world of digital logic.
Multiplexer(MUX) and Multiplexing
Two inputs means four possible input combinations. Try them all and fill out the 2-input NAND gate's truth table:. There are two parts to De Morgan's Law:. Prove it yourself! Build the circuit below with your LogicBlocks, and compare the truth table you filled out for the NAND gate with the truth table for this circuit -- two inverted inputs running into an OR gate.
Now, you might be asking: "what's the point? The circuits in the previous experiments have all been examples of combinational logic circuits. In combinational circuits the output depends exclusively on the current state of the inputs.A multiplexer is a combinational circuit that has 2 n input lines and a single output line.
Simply, the multiplexer is a multi-input and single-output combinational circuit. The binary information is received from the input lines and directed to the output line. On the basis of the values of the selection lines, one of these data inputs will be connected to the output. Unlike encoder and decoder, there are n selection lines and 2 n input lines. So, there is a total of 2 N possible combinations of inputs. A multiplexer is also treated as Mux.
On the basis of the combination of inputs which are present at the selection line S 0one of these 2 inputs will be connected to the output. On the basis of the combination of inputs that are present at the selection lines S 0 and S 1one of these 4 inputs are connected to the output. In the 8 to 1 multiplexer, there are total eight inputs, i. On the basis of the combination of inputs that are present at the selection lines S 0S 1, and S 2one of these 8 inputs are connected to the output.
In the 16 to 1 multiplexer, there are total of 16 inputs, i. On the basis of the combination of inputs that are present at the selection lines S 0S 1and S 2one of these 16 inputs will be connected to the output.
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In a couple of tutorials I've come across 12the table is presented as follows:. I've also come across other tutorials 345 that show the 2 to 1 multiplexer as I would expect it to be second caseand to me it seems the most consistent approach considering that all the larger multiplexers n to 1 shown in the tutorials follow this pattern. A multiplexer is a collection of gates where none are arranged to retain an internal state.
A truth table of all possible input combinations can be used to describe such a device. A multiplexer has 3 inputs. The truth tables in the question only has 4 entries and therefor falls short of describing a multiplexer. Interestingly, most of the links in the question have multiplexer truth tables that have 8 entries.
The switch diagrams are generally used in block diagrams where a multiplexer is part of a larger circuit. However, the more common symbol used look like this:. As for which input is passed through to the multiplexor's output based on the value of the selection line If pressed I would say the 3rd table is the expected behavior. I would expect a selection value of zero to pass the 1st input and a selection value of one to pass the 2nd and so on. That is not to say the 1st table is wrong.
It too represents a multiplexer. In fact, if all the selection lines were inverted in this case there is only 1 this would be the expected behavior.
Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 4 years, 2 months ago. Active 4 years, 2 months ago. Viewed 8k times. In a couple of tutorials I've come across 12the table is presented as follows: However, the same tutorials show the 4 to 1 multiplexor truth table as follows: If this is the case, then why is the 2 to 1 truth table not the following?
W5VO Jet Blue Jet Blue 9 9 silver badges 21 21 bronze badges. Active Oldest Votes. However, the more common symbol used look like this: As for which input is passed through to the multiplexor's output based on the value of the selection line I excluded the other values because they are 'don't care' values.
The expanded truth tables still follow the same pattern so this doesn't answer my question. I am curious about the discrepancy between the truth table and all the other n:1 multiplexers.
However, the zero outputs you have omitted are important. In a real circuit, you could implement your truth table by simply connecting the output to the positive rail of the supply. I see your confusion! Still, you shouldn't "condense" truth tables like thatDiagram Base Website Full Edition. Logic Diagram Of 8 To 1 Line Multiplexer The first step is to pick a suitable case for your own document, and the second step is to compose a few appropriate content.
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Digital Circuits - Multiplexers
Last, you will have the ability to obtain an idea of how to insert a Venn Diagram in Google Docs simply by going through the cases you have selected, and listing the information on just what the item is and where it's found. You may then mark the keywords and names you will have to use and create a final draft.
Just remember that every example is exceptional, which means you'll have to learn the keywords which are important for this example. User Blog. User Blog Global. Securely Verified.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. 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.It is quite opposite to multiplexer or MUX.
It is a process of taking information from one input and transmitting over one of many outputs. DEMUX are used to implement general-purpose logic systems. A demultiplexer takes one single input data line and distributes it to any one of a number of individual output lines one at a time. Demultiplexing is the process of converting a signal containing multiple analog or digital signals backs into the original and separate signals.
The 1 to 4 demultiplexer consists of one input, four outputs, and two control lines to make selections The below diagram shows the circuit of 1 to 4 demultiplexer. The input bit is Data D with two select lines A and B. Thus, only one data is transmitted at Y1. If D is low, then Y1 is low and if D is high, Y1 is high.
The value of Y1 depends on the value of D. Then D is transmitted to output Y2. A 1 to 8 demultiplexer consists of one input line, 8 output lines and 3 select lines.
Digital Circuits - De-Multiplexers
It is also called as 3 to 8 demux because of the 3 selection lines. Below is the block diagram of 1 to 8 demux. The below is the truth table for 1 to 8 demultiplexer. Using the above truth table the logic diagram of the demultiplexer is implemented using eight AND and three NOT gates.
The different combinations of the select lines select one AND gate at given time, such that data input will be seen at a particular output. A 1 to 8 demultiplexer can be implemented using two 1 to 4 demultiplexers. Implementation of large output demultiplexers becomes complex, so smaller demux is used to implement large demultiplexers.
This can be implemented using 1 to 8 demultiplexer, 1 to 4 demultiplexer and 1 to 2 demultiplexer. Therefore, this is the basic information about types of Demultiplexers. I hope you might have got some fundamental concepts about this topic.
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