FreeRangeVHDL：电子书免费下载

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"free_range_vhdl.pdf" 这是一本名为《FreeRangeVHDL》的电子书，由Bryan Mealy和Fabrizio Tappero共同编写。该书的版权为2011年，作者发布版本为1.03，日期为2012年1月13日。你可以免费从http://www.freerangefactory.org下载。作者在书中尽力确保内容的准确性，但不提供任何形式的明示或暗示保证，也不对错误或遗漏承担责任。如果因使用本书中的信息或程序导致任何间接或附带损失，作者概不负责。这本书遵循Creative Commons Attribution-ShareAlike Unported License（创意共享署名-相同方式共享未本地化许可协议）。这意味着读者可以不受限制地使用、分发、改编和复制本书内容，但必须正确引用原始作品。如果你基于此工作创建了新的内容，你可以在相同的、类似的或兼容的许可下分发这些新内容。要查看此许可的详细条款，可访问：http://creativecommons.org/licenses/by-sa/3.0/。作者鼓励读者提供反馈和贡献，他们非常乐意接受任何有助于改进、扩展或纠正书中内容的建议。《FreeRangeVHDL》这本书的核心主题是VHDL，一种用于硬件描述的语言。VHDL（Very High-Speed Integrated Circuit Hardware Description Language）被广泛用于数字逻辑系统的建模和设计，包括但不限于集成电路、FPGA（现场可编程门阵列）和ASIC（应用专用集成电路）的设计。通过学习VHDL，设计师能够用代码来描述硬件行为和结构，进行仿真验证，以及生成可综合的逻辑设计，最终实现硬件的自动化设计流程。本书可能涵盖了以下VHDL的关键知识点： 1. VHDL的基础语法：包括数据类型、实体、结构体、进程、运算符等基本概念。 2. 设计层次：从行为级到门级的转换，理解如何从高级抽象描述到低级逻辑门电路的映射。 3. 仿真与验证：使用VHDL进行设计的仿真，以便在实际制造之前检查其功能是否符合预期。 4. 综合：将VHDL代码转化为可编程逻辑器件的配置文件，如Xilinx或Altera的比特流文件。 5. 常见设计模式：介绍在VHDL设计中常用的设计模式和最佳实践。 6. 实例分析：通过具体的电路设计案例，展示如何应用VHDL进行硬件设计。 7. 错误处理和调试技巧：如何识别和修复VHDL代码中的错误。通过阅读《FreeRangeVHDL》，读者将能够深入理解VHDL语言，提升数字系统设计的能力，并掌握如何利用VHDL进行有效的硬件设计和验证。此外，由于作者欢迎反馈和贡献，读者有机会参与到书中内容的完善和更新，共同推动VHDL技术的发展。

2 Chapter 1: Introduction To VHDL

And if the circuit does actually work, it will most likely be ineﬃcient due to the fact

that the resulting hardware was unnecessarily large and overly complex. This problem

is compounded as the size and complexity of your circuits becomes greater.

There are two primary purposes for hardware description languages such as VHDL.

First, VHDL can be used to model digital circuits and systems. Although the word

“model” is one of those overly used words in engineering, in this context it simply

refers to a description of something that presents a certain level of detail. The nice

thing about VHDL is that the level of detail is unambiguous due to the rich syntax

rules associated with it. In other words, VHDL provides everything that is necessary

in order to describe any digital circuit. Likewise, a digital circuit/system is any circuit

that processes or stores digital information. Second, having some type of circuit model

allows for the subsequent simulation and/or testing of the circuit. The VHDL model

can also be translated into a form that can be used to generate actual working circuits.

The VHDL model is magically

interpreted by software tools in such a way as to create

actual digital circuits in a process known as synthesis.

There are other logic languages available to model the behavior of digital circuit

designs that are easy to use because they provide a graphical method to model cir-

cuits. For them, the tendency is to prefer the graphical approach because it has such

a comfortable learning curve. But, as you can easily imagine, your growing knowl-

edge of digital concepts is accompanied by the ever-increasing complexity of digital

circuits you are dealing with. The act of graphically connecting a bunch of lines on

the computer screen quickly becomes tedious. The more intelligent approach to digi-

tal circuit design is to start with a system that is able to describe exactly how your

digital circuit works (in other words, modeling it) without having to worry about the

details of connecting massive quantities of signal lines. Having a working knowledge

of VHDL will provide you with the tools to model digital circuits in a much more

intelligent manner.

Finally, you will be able to use your VHDL code to create actual functioning circuits.

This allows you to implement relatively complex circuits in a relatively short period

of time. The design methodology you will be using allows you to dedicate more time

to designing your circuits and less time “constructing” them. The days of placing,

wiring and troubleshooting multiple integrated circuits on a proto-board are gone.

VHDL is a very exciting language that can allow the design and implementation of

functions capable of processing an enormous amount of data by employing a relatively

low-cost and low-power hardware. Moreover, what is really impressive is that, via

simple VHDL modules, you can have direct access to basic ns-level logic events as

well as communicate using a USB port or drive a VGA monitor to visualize graphics

of modest complexity.

Modeling digital circuits with VHDL is a form of modern digital design distinct from

It is not really magic. There is actually a well-deﬁned science behind it.

1.1 Golden Rules of VHDL 3

schematic-based approaches. The programmer writes a loose description of what the

ﬁnal logic circuit should do and a language compiler, in this case called a synthesizer,

attempts to “infer” what the actual ﬁnal physical logic circuit should be. Novice pro-

grammers are not always able to convince the synthesizer to implement something

that seems very clear in their minds. A somehow old-fashioned alternative to a de-

scriptive language such as VHDL is one in which the programmer simply interconnects

a ﬁnite number of digital blocks that he has pooled from a library in an attempt to

reach the same objective. This approach is not only very time consuming but also

inherently limiting and very error prone.

Modern digital design is more about appropriately modeling digital circuits and

maintaining a quality description of the circuit. All that is left now is to learn how to

properly use VHDL to describe what you want to implement.

1.1 Golden Rules of VHDL

Before you start, here are a couple of points that you should never forget when work-

ing with VHDL.

VHDL is a hardware-design language. Although most people have probably al-

ready been exposed to some type of higher-level computer language, these skills are

only indirectly applicable to VHDL. When you are working with VHDL, you are not

programming, you are “designing hardware”. Your VHDL code should reﬂect this

fact. What does this mean? It means that unless you are inside certain constructs,

your code lines will be executed almost all at once. If your VHDL code appears too

similar to code of a higher-level computer language, it is probably bad VHDL code.

This is vitally important.

Have a general concept of what your hardware should look like. Although

VHDL is vastly powerful, if you do not understand basic digital constructs, you will

probably be unable to generate eﬃcient digital circuits. Digital design is similar to

higher-level language programming in that even the most complicated programming

at any level can be broken down into some simple programming constructs. There is a

strong analogy to digital design in that even the most complicated digital circuits can

be described in terms of basic digital constructs. In other words, if you are not able

to roughly envision the digital circuit you are trying to model in terms of basic digital

circuits, you will probably misuse VHDL, thus angering the VHDL gods. VHDL is

cool, but it is not as magical as it initially appears to be.

1.2 Tools Needed for VHDL Development

VHDL is a programming language used to implement hardware which will run other

software (for example C). A Field Programmable Gate Array (FPGA) is probably the

6 Chapter 2: VHDL Invariants

line in which the dashes appear. Listing 2.3 shows two types of commenting styles.

Unfortunately, there are no block-style comments (comments that span multiple lines

but do not require comment marks on every line) available in VHDL.

Listing 2.3: Two typical uses of comments.

-- This next section of code is used to blah-blah

-- This type of comment is the best fake for block-style commenting.

PS_reg <= NS_reg; -- Assign next_state value to present_state

Appropriate use of comments increases both the readability and the understandability

of VHDL code. The general rule is to comment any line or section of code that may

not be clear to a reader of your code besides yourself. The only inappropriate use of

a comment is to state something that is patently obvious. It is hard to imagine code

that has too few comments so don’t be shy: use lots of comments. Research has shown

that using lots of appropriate comments is actually a sign of high intelligence.

2.4 Parentheses

VHDL is relatively lax on its requirement for using parentheses. Like other computer

languages, there are a few precedence rules associated with the various operators in

the VHDL language. Though it is possible to learn all these rules and write clever

VHDL source code that will ensure the readers of your code are left scratching their

heads, a better idea is to practice liberal use of parentheses to ensure the human

reader of your source code understands the purpose of the code. Once again, the two

statements appearing in Listing 2.4 have the same meaning. Note that extra white

space has been added along with the parentheses to make the lower statement clearer.

Listing 2.4: Example of parentheses that can improve clarity.

if x = ’0’ and y = ’0’ or z = ’1’ then

blah; -- some useful statement

end if;

if ( ((x = ’0’) and (y = ’0’)) or (z = ’1’) )

blah; -- some useful statement

end if;

2.5 VHDL Statements

Similar to other algorithmic programming languages, every VHDL statement is termi-

nated with a semicolon. This fact helps when attempting to remove compiling errors

from your code since semicolons are often omitted during initial coding. The main

challenge then is to know what constitutes a VHDL statement in order to know when

to include semicolons. The VHDL synthesizer is not as forgiving as other languages

when superﬂuous semicolons are placed in the source code.

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FreeRangeVHDL：电子书免费下载

VHDL________.rar_VHDL doc_doc_ram vhdl

DA_TLC5620_vhdl.rar_DA_TLC5620_vhdl_TLC5620_TLC5620 vhdl_fpga v

Error (10500): VHDL syntax error at D208_11_SRQ_function3.vhd(14) near text "COMPONENT"; expecting ";", or an identifier ("component" is a reserved keyword), or "entity"和Error (10500): VHDL syntax error at D208_11_SRQ_function3.vhd(8) near text "END"; e

vivado怎么用tcl添加global文件

Error (10437): VHDL Association List error at jiayouji_all_2.vhd(217): positional associations must be listed before named associations

使用VHDL编写一个RTOS的操作系统

88e1111_rgmii.zip_88e1111 vhdl_88e1111 驱动_rgmii模式_rgmii vhdl

CLK <= '1'; wait until time >= 10 ns;Error (10552): VHDL expression error at ALU_4bit_tb.vhd(42): illegal time in expression

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