Digital-electronics 简明教程
Digital Electronics - Combinational Circuits
一个 combinational circuit ,也称为一个 combinational logic circuit ,是一个数字电子电路,其输出仅取决于当前输入。
A combinational circuit, also called a combinational logic circuit, is a digital electronic circuit whose output is determined by present inputs only.
组合逻辑电路的输出不依赖于电路操作的历史。换句话说,组合电路是一种数字逻辑电路,其输出仅取决于当前输入值,并不依赖于任何反馈或以前的输入或输出值。
The output of a combinational logic circuit does not depend on the history of the circuit operation. In other words, a combinational circuit is a digital logic circuit whose output depends only on the present input values and does not depend on any feedback or previous input or output values.
在本章中,我们将解释组合电路的基础知识、其框图、类型和应用。因此,让我们从组合电路的基本定义开始。
In this chapter, we will explain the fundamentals of combinational circuits, and its block diagram, types, and applications. So, let’s start with the basic definition of combinational circuits.
What is a Combinational Circuit?
组合电路是一种数字逻辑电路,其输出仅取决于当前输入值,并不取决于过去输入和输出值。因此,组合电路被认为在其电路中没有存储先前输入和输出的存储单元。相反,它由一定数量的输入线路(用于施加当前输入值)和一定数量的输出线路组成。
A combinational circuit is a type of digital logic circuit whose output depends on the present input values only and does not depend on past input and output values. Therefore, a combinational circuit is considered to not have a memory element in its circuit that stores previous inputs and outputs. Instead, it consists of a certain number of input lines to apply current input values and a certain number of output lines.
组合电路最重要的特征是它在输入和输出之间没有任何反馈路径。因此,组合电路可以归类为开环系统。
The most important characteristic of a combinational circuit is that it does not have any feedback path between input and output. Therefore, the combinational circuits can be categorized as open-loop systems.
Block Diagram of Combinational Circuit
下图描绘了组合逻辑电路的框图。
The following figure depicts the block diagram of a combinational logic circuit.
这里,我们可以看出,组合电路的电路图中只有三个关键元素,它们是:
Here, we can see that there are only three key elements in the circuit diagram of a combinational circuit, they are −
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Input Lines − The input lines are used to enter the input values into the combinational circuit.
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Processing Unit − It is the main element that processes the input values depending on the type of the circuit. For example, a full adder adds three binary bits.
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Output Lines − The output lines are used to take results generated by the circuit.
Characteristics of Combinational Circuits
以下是组合电路的主要特征:
The following are the main characteristics of combinational circuits −
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The output of a combinational circuit, at any instant of time, depends only on the present input values at that instant of time.
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Combinational circuits do not use any kind of memory element in their circuits. Thus, the previous state of input and output values do not have any effect on the present operation of the circuit.
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The output of a combinational circuit can be entirely predicted using its logical operation and input values.
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Combinational circuits produce an instantaneous output in response to any change in its input values.
Types of Combinational Circuits
在数字电子技术中,组合电路是数字系统的重要组成部分。根据执行的功能,组合电路有多种类型。下面将对一些常见的组合电路类型及其功能进行说明:
In digital electronics, the combinational circuits are important components of digital systems. Depending on the functions performed, there are various types of combinational circuits. Some common types of combinational circuits and their functions are explained below −
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Binary Adders
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Binary Subtractors
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Multiplexers (MUX)
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Demultiplexers (DEMUX)
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Encoders
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Decoders
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Comparators
在本章的以下部分,我们将简要讨论每一类组合电路及其功能。
In the following sections of this chapter, we will discuss briefly about each of these combinational circuits along with their functions.
Binary Adders
binary adder 是一个组合电路,执行二进制数字或位的加法。根据设计和配置,分为两种类型的二进制加法器,即半加法器和全加法器。
A binary adder is a combinational circuit that performs the addition of binary digits or bits. Depending on the design and configuration, there are two types of binary adders namely, Half Adder and Full Adder.
half adder 是一个具有两个输入和两个输出的组合逻辑电路。半加法器电路旨在将两个单比特二进制数 A 和 B 相加。它是将两个单比特数相加的基本构建模块。该电路有两个输出,即和与进位。
The half adder is a combinational logic circuit with two inputs and two outputs. The half adder circuit is designed to add two single-bit binary numbers A and B. It is the basic building block for the addition of two single-bit numbers. This circuit has two outputs namely, sum and carry.
full adder 旨在克服半加法器的缺点,即只能相加两个位。因此,全加法器是一个三输入和两个输出的组合电路。其中,输入是两个一位数字 A 和 B,以及前一个加法产生的进位 C。输出是和和进位输出。
The full adder is designed to overcome the drawback of a half adder which is the ability to add only two bits. Therefore, the full adder is a three-input and two-output combinational circuit. Where, the inputs are two one-bit numbers A and B, and a carry C from the previous addition. The outputs are sum and carry output.
Binary Subtractors
二进制减法器是一种组合逻辑电路,用于将一个二进制数减去另一个二进制数。类似于二进制加法器,有两种类型的二进制减法器,即半减法器和全减法器。
A binary subtractor is a combinational logic circuit used to subtract one binary number from another. Similar to binary adder, there are two types of binary subtractors namely, half-subtractor and full-subtractor.
half subtractor 是一个具有两个输入 (A 和 B) 和两个输出(差和借位)的组合电路。它产生输入处两个二进制位之间的差,还产生一个输出(借位)来指示是否借用了 1。在二进制减法 (A-B) 中,A 称为被减数位,而 B 称为减数位。
A half subtractor is a combination circuit with two inputs (A and B) and two outputs (difference and borrow). It produces the difference between the two binary bits at the input and also produces an output (Borrow) to indicate if a 1 has been borrowed. In binary subtraction (A-B), A is called a Minuend bit and B is called a Subtrahend bit.
full subtractor 也是一个组合电路,具有三个输入 A、B 和 Bin,以及两个输出 D 和 Bout。
The full subtractor is also a combinational circuit with three inputs A, B, and Bin, and two outputs D and Bout.
此处,A 是 minuend bit ,B 是 subtrahend bit ,Bin 是前一阶段产生的 previous borrow bit ,D 是差输出,Bout 是借位输出。
Here, A is the minuend bit, B is the subtrahend bit, Bin is the previous borrow bit produced by the previous stage, D is the difference output and Bout is the borrow output.
Multiplexers (MUX)
多路复用器是一种特殊类型的组合逻辑电路。它由 n 个数据输入线、一个输出和 m 个选择线组成。对于多路复用器,n = 2m。
A multiplexer is a special type of combinational logic circuit. It consists of n-data input lines, one output, and m-select lines. For a multiplexer, n = 2m.
多路复用器是一种数字电路,它选择 n 个数据输入之一并将其路由到输出线。n 个数据输入之一的选择由选择线完成。根据施加在选择线上的数字代码,选择“n”个数据输入之一并传输到输出线。
A multiplexer is a digital circuit that selects one of the n data inputs and routes it to the output line. The selection of one of the n data inputs is done by the select lines. Depending on the digital code applied at the select lines, one out of "n" data inputs is selected and transmitted to the output line.
在某些多路复用器中,还存在一个 enable input E ,在多路复用器的级联中很有用。
In some multiplexers, there is also an enable input E which is useful in cascading of multiple multiplexers.
根据输入线的数量,可以有多种类型的多路复用器。一些常见类型的多路复用器包括 2:1 多路复用器、4:1 多路复用器、16:1 多路复用器和 32:1 多路复用器。
Depending on the number of input lines, there can be several types of multiplexers. Some common types of multiplexers include 2:1 Multiplexer, 4:1 Multiplexer, 16:1 Multiplexer, and 32:1 Multiplexer.
Demultiplexers (DEMUX)
解复用器执行分配操作,即接收一个数据输入并将其分配到多个输出线。
A demultiplexer performs a distribution operation i.e., it receives one data input and distributes it over several output lines.
解复用器只有一个输入线,“n”个输出线和“m”个选择线。一次,仅由施加到选择线的数字代码选择一个输出线,并且数据输入传输到选定的输出线。
A demultiplexer has only one input line, "n" output lines, and "m" select lines. At a time, only one output line is selected by the digital code applied to the select lines and the data input is transmitted to the selected output line.
解复用器可以根据输出线的数量分类为各种类型。一些常用的解复用器类型包括:1:2 解复用器、1:4 解复用器、1:16 解复用器和 1:32 解复用器。
Demultiplexers can be classified into various types depending on the number of output lines. Some commonly used types of demultiplexers include: 1:2 Demultiplexer, 1:4 Demultiplexer, 1:16 Demultiplexer, and 1:32 Demultiplexer.
Encoders
编码器是一种组合电路,设计用于将一段信息转换为二进制代码。编码器具有 n 个输入线和 m 个输出线,其中 n = 2m 。
An encoder is a combinational circuit that is designed to convert a piece of information into a binary code. An encoder has n number of input lines and m number of output lines, where n = 2m.
编码器生成与施加在其上的数字输入相对应的 m 位二进制代码。换句话说,编码器接受 n 输入数字字并将其转换为 m 位另一个数字字。
An encoder generates an m-bit binary code corresponding to the digital input applied to it. In other words, an encoder accepts an n-input digital word and converts it into an m-bit another digital word.
编码器的示例包括 4 到 2 编码器、八进制到二进制编码器、十六进制到二进制编码器、优先级编码器等。
Examples of encoder include 4-to-2 encoder, octal-to-binary encoder, hexadecimal-to-binary encoder, priority encoder, etc.
Decoders
解码器是一种组合电路,它将二进制代码转换为正常字,例如十进制数字。解码器通常由 n 个输入线和 m 个输出线组成,其中 m = 2n 。
A decoder is a combinational circuit that converts a binary code into a normal word like a decimal digit. A decoder typically consists of n input lines and m output lines, where the m = 2n.
解码器广泛用于显示驱动器、数据分发系统等。
Decoders are widely used in display drivers, data distribution systems, etc.
一些常用的解码器类型包括 2 至 4 解码器、3 至 8 解码器、4 至 16 解码器、BCD 至七段解码器等。
Some of the commonly used types of decoders are 2 to 4 decoder, 3 to 8 decoder, 4 to 16 decoder, BCD to seven segment decoder, etc.
Comparators
比较器是一种组合逻辑电路,用于比较两个二进制数。比较器主要用于算术和控制电路中,以执行比较或逻辑运算。
A comparator is a combinational logic circuit developed to compare two binary numbers. Comparators are mainly used in arithmetic and control circuits to perform comparison or logical operations.
顾名思义,比较器比较输入值并检查它们是否相等或一个输入大于/小于另一个输入。
A comparator, as its name suggests, compares the input values and checks whether they are equal or one input is greater/less than the other input.
Limitations of Combinational Circuits
组合电路具有以下几个优点,例如运算速度快、电路简单、操作可预测等。然而,它们也确实有一些局限性,其中一些如下所列 −
Combinational circuits have several advantages such as fast operational speed, simpler circuit, predictable operation, etc. However, they do have several limitations too, some of which are listed below −
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Combinational circuits do not have any memory element. They are incapable to store history of circuit operation.
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Combinational circuits cannot be used to implement certain highly complex logic functions.
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Combinational circuits do not have any feedback mechanism. That makes the combinational circuits to have limited functionality.
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At large scale, combinational circuits have several design complexities that can result in poor performance and inefficient resource utilization.
Applications of Combinational Circuits
组合电路是各种数字设备和系统中的基本构建模块。它们广泛用于组合电路的若干数字设备中 −
Combinational circuits are the fundamental building blocks in various digital devices and systems. They are widely used in several digital devices in which combinational circuits are used −
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Microprocessors and Microcontrollers
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Digital Computers
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Calculators
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Digital Communication Systems
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Keyboards
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Smartphones and Digital Watches, etc
Conclusion
组合逻辑电路是各种数字设备和系统中的一个关键组件。它可以定义为数字组件的互联系统,其输出仅取决于输入的当前状态,而不取决于过去输入和输出值。
A combinational logic circuit is a key component in various digital devices and systems. It can be defined as an interconnected system of digital components whose output depends only on the present states of inputs and it does not depend on past input and output values.
在本章中,我们解释了组合电路的特性、限制和应用。
In this chapter, we explained the characteristics, limitations, and applications of combinational circuits.