Digital-electronics 简明教程

Programmable Logic Devices

@ {s0}是一组集成电路，它们被配置为执行各种逻辑功能。PLD在工程和技术领域发挥着重要作用，因为它们构成了创新的基础，并支持工程师开发自动化数字系统，以提高流程的灵活性和效率。此处，“可编程”是指定义一个可以在没有人工干预的情况下多次执行的功能。

Programmable Logic Devices (PLDs) are a collection of integrated circuits which are configured to perform various logical functions. PLDs play an important role in the field of engineering and technology, as they form the basis of innovation and support engineers to develop automated digital systems to improve process flexibility and efficiency. Here, "programmable" means defining a function that can be performed multiple times without human intervention.

可编程逻辑器件@ {s1}是集成电路。它们包含一系列与门和另一系列或门。基于可编程功能的阵列类型有三种类型的PLD。

Programmable Logic Devices (PLDs) are the integrated circuits. They contain an array of AND gates & another array of OR gates. There are three kinds of PLDs based on the type of array(s), which has programmable feature.

  1. Programmable Read Only Memory

  2. Programmable Array Logic

  3. Programmable Logic Array

将信息输入这些器件的过程称为@ {s2}。基本上，用户可以按照要求对这些器件或IC进行电气编程以执行布尔函数。此处，术语编程指的是硬件编程，而不是软件编程。

The process of entering the information into these devices is known as programming. Basically, users can program these devices or ICs electrically in order to implement the Boolean functions based on the requirement. Here, the term programming refers to hardware programming but not software programming.

在本节中，我们将讲解可编程逻辑器件的基本概念、类型、优点、局限性和应用。

In this chapter, we will explain the basic concepts of programmable logic devices, their types, advantages, limitations, and applications.

Programmable Read Only Memory (PROM)

只读存储器（ROM）是一种存储设备，永久存储二进制信息。这意味着，我们以后不能以任何方式更改该存储信息。如果ROM具有可编程功能，则称为@ {s3}。用户可以灵活地使用PROM编程器一次通过电气方式对二进制信息进行编程。

Read Only Memory (ROM) is a memory device, which stores the binary information permanently. That means, we can’t change that stored information by any means later. If the ROM has programmable feature, then it is called as Programmable ROM (PROM). The user has the flexibility to program the binary information electrically once by using PROM programmer.

PROM是一种可编程逻辑器件，具有固定的与阵列和可编程的或阵列。PROM的@ {s4}如下图所示。

PROM is a programmable logic device that has fixed AND array & Programmable OR array. The block diagram of PROM is shown in the following figure.

programmable read only memory

这里，AND 门的输入不是可编程的。因此，我们必须使用 n 个输入的 2n 个 AND 门生成 2n 个积项。我们可以使用 nx2n 解码器实现这些积项。因此，此解码器生成“n”个 min terms 。

Here, the inputs of AND gates are not of programmable type. So, we have to generate 2n product terms by using 2n AND gates having n inputs each. We can implement these product terms by using nx2n decoder. So, this decoder generates ‘n’ min terms.

这里，OR 门的输入是可编程的。这意味着，我们可以编程任意数量的必需积项，因为所有 AND 门的输出都被用作每个 OR 门的输入。因此，PROM 的输出将以 sum of min terms 的形式出现。

Here, the inputs of OR gates are programmable. That means, we can program any number of required product terms, since all the outputs of AND gates are applied as inputs to each OR gate. Therefore, the outputs of PROM will be in the form of sum of min terms.

Example

让我们使用 PROM 实现以下 Boolean functions 。

Let us implement the following Boolean functions using PROM.

\mathrm{A(X,Y,Z)\:=\:\sum m\left ( 5,6,7 \right )}

\mathrm{B(X,Y,Z)\:=\:\sum m\left ( 3,5,6,7 \right )}

给定的两个函数为最小项和的形式，每个函数具有三个变量 X、Y 和 Z。因此，我们需要一个 3 到 8 的解码器和两个可编程 OR 门来产生这两个函数。对应的 PROM 如图所示。

The given two functions are in sum of min terms form and each function is having three variables X, Y & Z. So, we require a 3 to 8 decoder and two programmable OR gates for producing these two functions. The corresponding PROM is shown in the following figure.

programmable or gates

在此，3 到 8 解码器生成 8 个最小项。两个可编程 OR 门可以访问所有这些最小项。但是，只有所需的最小项被编程以便由每个 OR 门生成对应的布尔函数。符号“X”用于可编程连接。

Here, 3 to 8 decoder generates eight min terms. The two programmable OR gates have the access of all these min terms. But, only the required min terms are programmed in order to produce the respective Boolean functions by each OR gate. The symbol ‘X’ is used for programmable connections.

What is a Programmable Logic Device?

可编程逻辑器件 (PLD) 可以定义为可以编程以执行特定功能的集成电路 (IC)。在这里，编程意味着我们可以定义一组指令，这些指令可以被执行多次以执行功能，而不需要任何人工干预。

A Programmable Logic Device (PLD) can be defined as an integrated circuit (IC) which can be programmed to perform specific functions. Here, programming means we can define a set of instructions that can be executed to perform the functions multiple times without need of any human intervention.

开发 PLD 的主要需求是实现可以复制传统逻辑电路行为并多次复制它们的数字逻辑功能。然而，PLD 与普通的数字逻辑电路在可编程性方面不同，这意味着我们可以通过在器件中设置指令集合来定义所需的逻辑功能。

The primary need of developing PLDs is occurred to implement digital logic functions that can copy the behavior of conventional logic circuits and replicate it many times. However, the PLDs are different from normal digital logic circuits in terms of programmability, which means we can define the desired logic functions by setting a collection of instructions in the device.

Types of PLDs

根据所使用的器件类型，可编程逻辑器件 (PLD) 可分为以下两种类型：

Based on the type of device used, Programmable Logic Devices (PLDs) can be classified into the following two types −

  1. Bipolar PLDs

  2. CMOS PLDs

让我们详细讨论每种类型的可编程逻辑器件。

Let us discuss each type of programmable logic device in detail.

Bipolar PLDs

双极型 PLD 是一类可编程逻辑器件，其中双极结型晶体管 (BJT) 是主要功能器件。双极型 PLD 是可编程逻辑器件的较早版本。因此，它们在 CMOS PLD 开发之前被广泛使用。

Bipolar PLDs are the types of programmable logic devices in which Bipolar Junction Transistor (BJT) is the main functional device. Bipolar PLDs are the older versions of programmable logic devices. Thus, they were commonly used before the development of CMOS PLDs.

以下是双极性可编程逻辑器件的一些重要特性：

The following are some important characteristics of the bipolar programmable logic devices −

  1. Bipolar PLDs provide fast switching speeds and hence they can operate at higher frequencies.

  2. Bipolar PLDs are better suited for applications involving rapid signal processing and require fast response times.

  3. Bipolar PLDs require more power to operate.

  4. Bipolar PLDs have better immunity to electronic noise and interference.

所有这些特性都使双极性可编程逻辑器件非常适合在高速运行和可靠性至关重要的应用中使用，例如航空航天、军事和电信系统。

All these characteristics make the bipolar programmable logic devices well-suited to use in the applications where high-speed operation and reliability are critical, such as aerospace, military, and telecommunications systems.

CMOS PLDs

CMOS PLD 代表互补金属氧化物半导体可编程逻辑器件。顾名思义，CMOS PLD 使用 CMOS 晶体管，即 NMOS（N 沟道金属氧化物半导体）和 PMOS（P 沟道金属氧化物半导体）晶体管作为基本组件。

CMOS PLDs stand for Complementary Metal Oxide Semiconductor Programmable Logic Devices. As their name implies, CMOS PLDs use the CMOS transistors i.e., NMOS (N-channel Metal Oxide Semiconductor) and PMOS (P-channel Metal Oxide Semiconductor) transistors as the fundamental component.

CMOS PLD 基本上是 PLD 的现代版本，并且由于它具有众多优势而被广泛用于现代数字系统中。

CMOS PLDs are basically the modern versions of PLDs and are widely used in modern digital systems due to their numerous advantages.

CMOS PLD 的一些重要特性如下所述 -

Some important characteristics of CMOS PLDs are described below −

  1. CMOS PLDs require very less amount of power to operate. Hence, this characteristic makes the CMOS PLDs well-suited to use in battery-power devices where energy efficiency is an important factor.

  2. CMOS PLDs are more reliable and robust. As they are designed to withstand against various environmental factors like high/low temperatures, voltage fluctuations, and different radiation interferences.

  3. CMOS PLDs are also excellent in terms of scalability.

CMOS PLD 是较新的 PLD 设备，因此在各种现代电子设备中非常常用，如消费电子产品、医疗设备、工业自动化系统、汽车系统。

CMOS PLDs are newer PLD devices and hence are very commonly used in various modern electronics devices like consumer electronics, medical equipment, industrial automation systems, automotive systems.

PLD Programming Languages

在可编程逻辑设备 (PLD) 的情况下，有几种不同类型的硬件描述语言 (HDL) 用于对其进行编程。使用这些 PLD 编程语言，工程师和设计人员可以定义 PLD 电路的行为和逻辑功能。

In the case of programmable logic devices (PLDs), several different types of Hardware Description Languages (HDLs) are used to program them. Using these PLD programming languages, engineers and designers can define the behavior and logical functionality of the PLD circuit.

一些最常用的 PLD 编程语言在此处进行描述 -

Some of the most commonly used PLD programming languages are described here −

VHDL

VHDL 代表 VHSIC 硬件描述语言。这是一种标准化的硬件描述语言，用于对数字电路和系统进行建模和仿真。使用 VHDL，工程师和开发人员可以指定数字电路的结构和功能。由于 VHDL 同时支持并发和顺序描述，因此它是适合组合电路和顺序电路的最佳编程语言。

VHDL stands for VHSIC Hardware Description Language. It is a standardized hardware description language used for modelling and simulating digital circuits and systems. Using VHDL, engineers and developers can specify the structure and functionality of the digital circuits. VHDL is a best suited programming language for both combinational and sequential circuits because of its concurrent and sequential descriptions support.

VHDL 是最广泛用于设计和验证 PLD、ASIC、FPGA 等高度复杂数字电路和系统的一种编程语言。

VHDL is one of the most widely used programming language for designing and verification of highly complex digital circuits and systems like PLDs, ASICs, FPGAs, and more.

Verilog

Verilog 也是一种硬件描述语言 (HDL)，用于设计和编程 PLD。与 VHDL 类似，Verilog 还支持并发和顺序描述，使工程师和设计人员能够定义数字电路的结构和行为。

Verilog is also a Hardware Description Language (HDL) used for designing and programming of PLDs. Similar to VHDL, Verilog also supports the concurrent and sequential descriptions that empower engineers and designers to define the structure and behavior of digital circuits.

这种编程语言最常用于半导体行业，用于设计和编程不同类型的数字系统。

This programming language is most commonly used in semiconductor industries for designing and programming different kinds of digital systems.

PALASM

PALASM 代表可编程阵列逻辑汇编器。它是另一种用于编程可编程逻辑设备 (PLD) 的硬件描述语言 (HDL) 和汇编器。在 PALASM 的情况下，PLD 的行为、逻辑功能和结构使用文本语言格式进行描述。因此，开发人员必须编写 PALASM 代码来描述所需的逻辑功能和互连。之后，这些代码将被组装成适合可编程逻辑设备的格式。

PALASM stands for Programmable Array Logic Assembler. It is another Hardware Description Language (HDL) and Assembler used for programming programmable logic devices (PLDs). In the case of PALASM, the behavior, logic function, and structure of PLDs are described using a textual language format. Thus, the developers have to write PALASM code to describe the desired logic functions and interconnections. After that these codes are assembled into a format which is suitable for programmable logic devices.

然而，PALASM 是一种较旧的硬件描述语言，在 1980 年代和 1990 年代初被非常普遍地用于开发基于 PLD 的逻辑电路。

However, PALASM is an older hardware description language that was very commonly used in the 1980s and early 1990s for developing PLD-based logic circuits.

ABEL

ABEL 代表高级布尔表达式语言。它是一种高级硬件描述语言，专为编程可编程逻辑设备 (PLD) 而开发。

ABEL stands for Advanced Boolean Expression Language. It is a high-level hardware description language developed for programming the Programmable Logic Devices (PLDs).

在 ABEL 中，逻辑方程、真值表和寄存器传输级设计描述是使用清晰易读的语法指定的。然后，ABEL 编译器将所有这些设计描述转换为适合对所需的 PLD 进行编程的格式。ABEL 是 1990 年代非常普遍的易用的硬件描述语言。

In ABEL, the logic equations, truth tables, and register transfer level design descriptions are specified using a clearly readable syntax. Then, the ABEL compiler translates all these design descriptions into a format suitable for programming the desired PLDs. ABEL was a very commonly used user-friendly hardware description language in the 1990s.

CUPL

CUPL 代表通用可编程逻辑编译器。它是另一种用于编程不同类型的 PLD 的硬件描述语言和编译器。在这种编程语言中，逻辑函数、真值表和顺序逻辑指令是以简单语法形式指定的。

CUPL stands for Compiler for Universal Programmable Logic. It is another Hardware Description Language (HDL) and Compiler used for programming different kinds of PLDs. In this programming language, the logic functions, truth tables, and sequential logic instructions are specified in the form of simple syntax.

这种 HDL 语言在 1990 年代和 2000 年代初也很流行，并用于设计基于 PLD 的逻辑电路。

This HDL language was also very popular in the 1990s and early 2000s and was used for designing PLD based logic circuits.

所有这些都是用于设计和编程可编程逻辑设备的一些重要编程语言。PALASM、ABEL 和 CUPL 语言主要用于低复杂度设备。而 VHDL 和 Verilog 用于编程现代高度复杂的 PLD。

All these are some important programming languages used to design and program the programmable logic devices. The languages PALASM, ABEL, and CUPL are mainly in low-complexity devices. Whereas, VHDL and Verilog are used to program the modern highly-complex PLDs.

Advantages of Programmable Logic Devices

可编程逻辑器件 (PLD) 拥有众多优点，使其成为数字系统设计领域至关重要的工具。可编程逻辑器件的一些重要好处如下：

Programmable Logic Devices (PLDs) have numerous advantages that make them vital tools in the field of digital system design. Some of the important benefits of programmable logic devices are listed here −

  1. Programmable logic devices (PLDs) are easy to program and reprogram. Hence, they provide significant flexibility in terms of designing and implementation of a variety of logic functions.

  2. PLDs allow for designing custom logic circuits to fulfil the specific requirements of applications. This can be done by programming the internal logic circuits of the device.

  3. PLDs can be used in prototyping and testing of digital circuits which help in new product development at a faster rate. By speeding up the product development process, PLDs help to reduce the time and cost involved in hardware design.

  4. PLDs provide a fast and cost-effective way of developing medium to complex digital logic circuits and systems. PLDs help to develop simple, less expensive, and compact digital systems by integrating a large number of logic functions and components into a single device.

  5. PLDs also support modern processing techniques like parallel processing, pipeline processing, etc. This feature helps to achieve high performance by simultaneous execution of logic functions.

Limitations of Programmable Logic Devices

如上所述，可编程逻辑器件 (PLD) 提供了若干优点，但它们也具有一定的局限性。以下是可编程逻辑器件的一些主要局限性：

Programmable Logic Devices (PLDs) offer several advantages as discussed above, but they also have certain limitations. The following are some of the key limitations of programmable logic devices −

  1. A programmable logic device can be designed to support a finite number of logic functions and elements. Thus, the implementation of complex digital circuits may require multiple devices.

  2. A PLD typically has a fixed number of input/output (I/O) pins. This limitation can cause an issue in terms of connectivity and interfacing with external/peripheral devices.

  3. Programming a PLD requires knowledge of Hardware Description Languages (HDLs) and design tools. Sometimes PLDs can malfunction due to unintentional reprogramming or data corruption.

  4. PLDs do not have inherent support for complex arithmetic operations and other high-level programming operations that are used in general purpose processors. Therefore, developers have to implement such operations and functionalities through custom logic designs.

Applications of Programmable Logic Devices

可编程逻辑器件 (PLD) 被广泛用于跨越不同领域和行业的广泛应用中，以设计数字逻辑电路和实现各种逻辑功能。可编程逻辑器件的一些常见应用如下：

Programmable Logic Devices (PLDs) are used in a wide range of applications across different fields and industries to design digital logic circuits and implement various logic functions. Some common applications of programmable logic devices are listed below −

  1. PLDs are widely used in embedded systems to perform different real-time operations like controlling, interfacing, and processing of data.

  2. In the field of digital signal processing, PLDs are used to design digital filters, develop modem algorithms, perform signal processing, etc.

  3. PLDs play an important role in communication systems, as they help in performing various operations like signal routing, data encryption and decryption, protocol conversion, and more.

  4. In the field of aerospace and defence, PLDs are employed for accomplishing various critical functions like flight control, operating radar systems, guiding missiles, encryption of confidential data and more.

  5. PLDs are also used in robotics and industrial automation to control and monitor the operations of machinery.

  6. In medical equipment, PLDs are used for automated high-speed data processing, real-time analysis of medical data, patient monitoring, etc.

Conclusion

总之，可编程逻辑器件是一种可以编程或训练来执行特定逻辑功能的数字器件。它主要用于在各种应用中实现自动化和提高效率的目的。

In conclusion, a programmable logic device is a digital device that can be programmed or trained to perform a specific logic function. It is primarily used for automation and efficiency improvement purposes in various applications.

在本章中，我们解释了可编程逻辑器件的基础知识、类型、优势、局限性和应用。在下一章中，我们将探讨不同类型的可编程逻辑器件以及它们的特性。

In this chapter, we explained the basics, types, advantages, limitations, and applications of PLDs. In the upcoming chapter, we will explore different kinds of programmable logic devices along with their features and characteristics.