Pdf version a multiplexer, abbreviated mux, is a device that has multiple inputs and one output. When the enable is true low, an output will go true based. What are the uses of multiplexer, demultiplexer, encoder and. Prerequisite encoder, decoders binary code of n digits can be used to store 2 n distinct elements of coded information. Multiplexers it is a device that selects one of several analog or digital input signals and forwards the selected input into a single line, a multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output. Multiplexers combinational logic functions electronics.
Objectives practicing the implementation of logic functions using msi level functional blocks. We can implement 1x8 demultiplexer using lower order multiplexers easily by considering the above truth table. An encoder is a combinational circuit that converts binary information in the form of a 2 n input lines. Difference between multiplexer and decoder difference. Read part this is the rf design at the level of registers and multiplexers. Its output is a twobit number x1x0, representing that count in binary. This text introduces the most important of these digital circuits. That was for a, b, c 0, 0, 0, which matches your answer. Digital circuits, often called integrated circuits or ics, are the central building blocks of a central processing unit cpu. When w1 the operation is reversed and the lower decoder is. Encoder decoder and multiplexer electrical engineering. Oct 30, 2015 this is a lecture on digital design specifically decoders and multiplexers.
The block diagram of 3 to 8 decoder using 2 to 4 decoders is shown in the following figure. Digital circuitsencodersdecoders wikibooks, open books. The block diagram of 1x16 demultiplexer using lower order multiplexers is shown in the following figure. Sep, 2011 multiplexer logic and symbol, decoders logic and symbol, logic function implementation using a multiplexer.
Examples are given on how to use these logic devices in digital circuits lecture by james m. Lecture 9 multiplexer, decoder, and pld ssi smallscale integration nand, nor, not, flip flop etc gate count multiplexers, decoders, registers, counters gate count multiplexers. Sn74ls47n datasheet bcd to 7 segment encoder, decoder. Multiplexerdecoder implementation of logic functions. Multiplexers when the control input a is 0, data input i 0 will be connected to the output z i. Spring 2011 ece 331 digital system design 12 decoders a decoder has n inputs 2n outputs a decoder selects one of 2 n outputs by decoding the binary value on the n inputs. Most of the standard example circuits, such as binary adders, decoders, multiplexers, etc. A multiplexer takes compatible audio and video and sometimes subtitles, chapter lists and combines them into one file that will play back easiest in a media player. N3 selects first decoder when it is low 0 less significant. Multiplexing and decoding are two different concepts, though they may look similar. Multiplexing is the process by which the output at any time shall be any one of the 2n inputs possible. Decoders are frequently used in communication systems such as wireless communication, networking, telecommunication, etc.
What are the uses of multiplexer, demultiplexer, encoder. The multiplexer routes one of its data inputs d0 or d1 to the output q. Although they appear similar, they certainly perform di. Spring 2011 ece 331 digital system design 3 multiplexers a multiplexer has 2n data inputs n control inputs 1 output a multiplexer routes or connects the selected data input to the output. While knowledge of the standard circuits is crucial for building more complex circuits, these standard circuits might not capture the students interest as much as a complete system. N to m decoders given n inputs, it outputs m lt 2n minterms. Multiplexers are also known as data n selector, parallel to serial convertor, many to one circuit, universal logic circuit. It takes 2n inputs and gives out n outputs,the enable pin should be kept 1 for enabling the circuit. Dandamudi, fundamentals of computer organization and design, springer, 2003. It is a combinational logic function that has 2n or fewer input lines and n output lines. What is the difference between a multiplexer and a decoder. Now do the same for the other 15 rows in the table. Ones complement uses an endaround carry if the carry bit is 1, which.
Internally, these decoders look very much like the circuits above. Read regis ter numbe r 1 read data 1 read data 2 read register number 2 register file write regi ster write data write 5 5 32 32 m u x r egi t r0 r gist r1 registern1 registern m u x re ad t 1. Implementing functions using decoders any nvariable logic function, in canonical sumofminterms form can be implemented using a single nto2 n decoder to generate the minterms, and an or gate to form the sum. In the figure two 38 decoders are used to build a 416 decoder. Difference between multiplexer and encoder multiplexer. Encoders turn readable information into a different format for example a cd track into an mp3. The complement of input a 2 is connected to enable, e of lower 2 to 4 decoder in order to get the outputs, y. Combinational logic circuits are defined by the logical function.
Information furnished by analog devices is believed to be accurate and reliable. Typical examples include 2to4 decoders 3to8 decoders 4to16 decoders due to the prevalence of decimal arithmetic, we also have 4to10 decoders. Multiplexer logic and symbol, decoders logic and symbol, logic function implementation using a multiplexer. Multiplexers are equated with 2to1, 4to1, 8to1 or combination of inputs, then decoder which is equated with 2. The most common types of binary decoders used in digital electronics are 2to4, 3to8, and 4. Cascading two 3to8 decoders to obtain a 4to16 decoder.
Dec 22, 2017 based on your tags, im guessing youre talking about audiovideo files. Whereas, an encoder is also considered a type of multiplexer but without a single output line. A 3to8 decoder simple view here is the symbol that might be used to represent a 3to8 decoder. A somewhat more complex 2to1 mux has one additional input often called enable.
A multiplexer or mux is a combination circuit that contains more than one input line, one output line and more than one selection line. Multiplexers and demultiplexers are often confused with one another by students. The simplest encoder is a 2nton binary encoder, where it has only one of 2n inputs 1 and the output is the nbit binary number corresponding to the active input. Therefore, we require two 2 to 4 decoders for implementing one 3 to 8 decoder. The schematic symbol for multiplexers is the truth table for a 2to1 multiplexer is using a 1to2 decoder as part of the circuit, we can express this circuit easily. Encoders an encoder is a combinational circuit that converts binary information in the form of a 2 n input. Objectives practicing the implementation of logic functions using msi level functional blocks, gaining experience with msi level functional blockscomponents whose outputs are. Multiplexers, decoders, and seven segment displays purpose learn about multiplexers muxs, decoders and seven segment displays. A combinational circuit that converts binary info from n inputs into a max. Binary code of n digits can be used to store 2 n distinct elements of coded information. Multiplexers and decoders 21 1 logic functions realized with mux 4to1 mux can. Draw and simulate the complete mixedlogic circuits in quartus. Jul 17, 2017 encoders work in exactly the opposite way as decoders, taking inputs, and having n outputs.
If you dont understand what i just did, you probably need to go back and learn what decoders and muxes do. In some cases, decoders have less than 2n input lines, so at least one output pattern gets repeated for different input values. Decoders and multiplexers 1 decoders and multiplexers cs147 lecture 6. Shown here is a multiplexer and a demultiplexer, each using a multipleposition switch symbol to indicate the selection functions inside the respective circuits. Q 1 consider the multiplexer based logic circuit shown in the figure. Using practical examples in teaching digital logic design. Design a circuit that counts the number of 1s present in 3 inputs a, b and c. Combinational logic implementation using decoders, encoders. The purpose of this laboratory is to introduce and familiarize the student with multiplexers and decoders, medium scale integration msi components that will be used to implement one combinational logic network and several multiplexed communication channels. Use the recommended development directory structure to perform modelsim simulations and.
A multiplexer, abbreviated mux, is a device that has multiple inputs and one output. The output lines of the decoder corresponding to the minterms of the function are used as inputs to the or gate. The decoder generates all of the minterms of the n input variables. The value of the control inputs determines the data input that is selected. T here are two data inputs d0 and d1, and a select input called s. When connecting a logic circuit with the outside world, incoming information from a keyboard or other input device must be changed encoded into an appropriate binary form. A demultiplexer or dmux is a combination circuit that contains one data input, few control inputs and many outputs, whereas a decoder is a logic circuit that converts a binary number to its equivalent decimal number. When the enable input is 0, neither i 0 nor i 1 is allowed through, and the output is always 0. Also before binary data produced by the digital system can be used by an output. The 3 less significant input lines n2, n1, n0 are connected to the data inputs of each decoder the most significant input line n3 is used to select between the two decoder circuits.
Notice how nand gates are used instead of ands as ive used above. Smaller decoders with enable lines can be used to build bigger decoders. Sn74ls47n datasheet bcd to 7 segment encoder, decoder, pdf, pinout, equivalent, replacement, schematic, manual, data, circuit, parts, datasheet. Decoders and multiplexers decoders a decoder is a circuit which has n inputs and 2 n outputs, and outputs 1 on the wire corresponding to the binary number represented by the inputs. June 23, 2003 basic circuit design and multiplexers 11 a 2to1 multiplexer here is the circuit analog of that printer switch.
For example, a 24 decoder might be drawn like this. When the enable is true low, an output will go true based on the binary pattern placed on a1. The efficiency of communication system can be increased considerably using multiplexer. When the enable input is 0, neither i 0 nor i 1 is allowed. Since signal 0 is a 1 from the decoder, and since the mux routes input 0 to the output, the output f from the mux is 1. Ppt decoders and multiplexers powerpoint presentation. To understand how a computer works, it is essential to understand the digital circuits which make up the cpu.
A decoder undoes this encoding to make the file readable, for example windows media player it also. We can implement 16x1 multiplexer using lower order multiplexers easily by considering the above truth table. To understand the demultiplexer and decoders the concept of combinational circuits must be clear. Communication system communication system is a set of system that enable communication like transmission system, relay and tributary station, and communication network. Multiplexers are mainly used to increase amount of the data that can be sent over the network within certain amount of time and bandwidth. The data inputs of upper 8x1 multiplexer are i 15 to i 8 and the data inputs of lower 8x1 multiplexer are i 7 to i 0. Encoders convert 2 n lines of input into a code of n bits and decoders decode the n bits into 2 n lines. The outputs of upper 1x8 demultiplexer are y 15 to y 8 and the outputs of lower 1x8 demultiplexer are y 7 to y 0. When the enable is false high, all outputs are false. The outputs of upper 1x4 demultiplexer are y 7 to y 4 and the outputs of lower 1x4 demultiplexer are y 3 to y 0. Decoders, encoders, multiplexers, demultiplexers implementing. Based on your tags, im guessing youre talking about audiovideo files. When a bit comes in on an input wire, the encoder outputs the physical address of that wire. These are specialized 4to16 decoders with six fewer pins.
Encoders and decoders in digital logic geeksforgeeks. What are the everyday applications of decoders encoders. By adding or gates, we can even retain the enable function. Multiplexers also generate speed of data transmission over a period of time and decoders distribute them on various network systems.