Type analysis of demultiplexer (demultiplexer)

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Preface

In Digital , We all learned about data selectors （MUX）, Commonly used 4 choose 1 Data selector 、8 choose 1 Data selector , For data selection switching , Select a specified combinational logic circuit from a group of input signals to the output , Multiple input and one output , The common form is like this ：

But sometimes we only have one input , However, this input is required to correspond to different output ports according to different states of the input address code , At this time, a specific functional circuit is needed .
And data selector Multiplexer relative , be called Demultiplexer, It's called a demultiplexer , Also known as multiplexer , The basic logical structure is as follows ：

DEMUX It is used to realize general logic system . The demultiplexer allocates one input data line to any one of several individual output lines at a time . Demultiplexing is the process of converting a signal containing multiple analog or digital signals back to the original and individual signals .2^n The demultiplexers with outputs are n Select lines .

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One 、Demultiplexer Basic types

1. 1 to 2 Demultiplexer

Start with the simplest ,1 to 2 Channel demultiplexer . Because it is 2 Channel output signal , Then the input control signal is 1 position .

The input data bits are Input IN The signal , There is a selection line S, The input bit can be transferred to two different output bits according to the input state of the selection line .

2. 1 to 4 Demultiplexer

1 to 4 Channel demultiplexer is the most common type of multiplexer , Because more output states can be controlled at the same time , It can also be extended as a basic module to 1 to 8 Channel demultiplexer 、1 to 16 Channel demultiplexer .
4 Channel output , Two bit control signal ：

Logic circuit diagram as follows ：

The input bit is data D, There are two selection lines A and B. Input bit D Transmitted to four output bits Y0、Y1、Y2 and Y4.
When AB by 01 when , The second and gate above is enabled . If D For low , be Y1 For low ; If D For the high , be Y1 For the high .Y1 Depends on D Value .

Truth table as follows ：

3. 1 to 8 Demultiplexer

1 to 8 The demultiplexer includes an input line ,8 Output lines 3 Select lines . Because of 3 Selection lines , It's also called 3 To 8 Splitter . Set the input for the Input ,S0、S1、 S2 There are three selection lines , Y0 To Y7 There are eight output lines .

It's not hard to imagine. ,1:8 Demux There are many ways to build , The two most common ways are to build and pass directly 1:4 Demux structure .
Build... Directly

adopt 1:4 Demux structure

Truth table

4. 1 to 16 Demultiplexer

Empathy ,1:16 Demux There are more diverse ways to build , It can be built directly or through 1:2 Demux、1:4 Demux、1:8 Demux Completion of construction .
Build... Directly
16 Output signal line , You need to 4 Control signal line ; The output is connected 16 An and gate , Each and gate has four inputs .

adopt 1:2 Demux And 1:8 Demux

adopt 1:4 Demux structure

Truth table

Two 、 Application of demultiplexer

The most intuitive is to use it in the communication system as a parallel control line to connect different devices .

• Demultiplexer for reconstructing parallel data and ALU circuit .
• The demultiplexer receives the output signal of the multiplexer , And convert back to the original form of data at the receiving end . The multiplexer and demultiplexer jointly perform the communication process .
• The demultiplexer helps to ALU The output of is stored in ALU In multiple registers and storage units in the circuit .ALU The data output of is fed to the demultiplexer as a data input . Each output of the demultiplexer is connected to multiple registers that can be stored in registers .
• The serial parallel converter is used to reconstruct parallel data from the input serial data stream . In this technology , The serial data from the incoming serial data stream is used as the input of the demultiplexer at fixed intervals . The counter is connected to the control input of the demultiplexer . This counter indicates the data signal output of the demultiplexer storing these data signals . When all data signals have been stored . The output of the demultiplexer can be retrieved and read in parallel .

reference

1. Different Types of Demultiplexers
2. Difference between Decoder and Demultiplexer
3. Demultiplexer demultiplexes symbols
4. Can you design a 1:16 decoder using a 1:4 decoder?