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1、 基于虚拟仪器的可重构逻辑摘要：从使用一个一般组合的通用计算机数据采集系统得出结果的虚拟仪器是为了仿真一个传统的测量仪器。该虚拟仪器的数据采集硬件提供电脑的输入/输出功能，通常以有固定架构的标准电路为基础。与此同时，软件定义的分析和处理所获得的数据是生成的虚拟仪器的功能。因此，虚拟仪器的特点是多功能性，成本低，但它们程序的性能缺乏面向应用的硬件架构。在本文中，我们提出了虚拟仪器系统在可重构硬件基础上改善了维护其多功能性虚拟仪器的特征和低成本。 1.引言 虚拟仪器的出现是测量仪器发展历史上的一场革命。它充分利用最新的计算机技术来实现和扩展仪器的功能，用计算机屏幕可以简单地模拟大多数仪器的调节控制
2、面板，以各种需要的形式表达并且输出检测结果，用计算机软件实现大部分信号的分析和处理,完成大多数控制和检测功能。用户通过应用程序将一般的通用计算机与功能化模块硬件结合起来,通过友好的界面来操作计算机,就像在操作自己定义，自己设计的单个仪器,可完成对被测量的采集，分析，判断，控制，显示，数据存储等。虚拟仪器较传统仪器的优点(1)融合计算机强大的硬件资源,突破了传统仪器在数据处理，显示，存储等方面的限制，大大增强了传统仪器的功能。(2)利用计算机丰富的软件资源，实现了部分仪器硬件的软件化，节省了物质资源，增加了系统灵活性。通过软件技术和相应数值算法，实时，直接地对测试数据进行各种分析与处理，通过图形
3、用户界面技术,真正做到界面友好、人机交互。(3)虚拟仪器的硬件和软件都具有开放性，模块化，可重复使用及互换性等特点。因此，用户可根据自己的需要，选用不同厂家的产品,使仪器系统的开发更为灵活，效率更高，缩短系统组建时间。传统的仪器是以固定的硬件和软件资源为基础的specific系统， 这使得系统的功能和应用程序由制造商定义。这些仪器都是复杂的系统，因此它们变得昂贵而且难以操作和管理。个人电脑在许多科技领域的广泛应用使其为测量仪器的执行搭建了一个理想的硬件和软件平台，通过增加一个简单的数据采集系统，个人计算机可以仿真任何仪器。因为它们没有独自占有和访问硬件和软件资源，所以以这种方式产生的仪器被称为
4、虚拟仪器。不同的仪器只要对该软件重新编程就可以在同一硬件中实现。虚拟仪器呈现了大量的优势，其中最重要的就是由于硬件和软件资源的重用性降低了成本。上述特点及虚拟仪器的不断发展和个人电脑降价使虚拟仪器成为传统仪器的一个有价值的替代。然而，也有两个主要因素限制了虚拟仪器的应用。一方面，数据捕获的减少将放缓速度，因为一般用途的电脑普遍常用的操作系统并不面向实时应用。另一方面，数据采集系统不是应用导向系统而是一个通用的系统。因此，我们建议的重点是由通用硬件更换可重构数据采集系统来加强虚拟仪器，它如图1所示。通过这种方式，一些数据的处理过程可以通过减少计算机上硬件数据流和上升的最大采样率来实现。图1.以重
5、构逻辑为基础的虚拟仪器基于可重构逻辑的虚拟仪器好处如下： -该仪器的带宽可以提高，为在硬件上实现关键算法提供更多的时间。-输入/输出的容量根据不同的应用可以重新配置。在特殊情况下的FPGA器件的特点是通过大量输入/输出引脚提供的能力来观察和控制的全数字信号的虚拟仪器。 -计算机接口可根据现有的资源重新配置（即插即用外设）。 -不同的仪器可以共享软件和硬件设计模块提高了它们的可重用性。 2.虚拟仪器的组成及分类虚拟仪器系统主要由计算机、硬件板卡、软件及附件组成。用户可以根据要求灵活地构建自己的测试仪器。虚拟仪器的核心是软件，它主要由硬件驱动程序、系统操作平台、应用编程软件等组成，可完成所有的测试
6、要求。目前开发环境主要有两类：(1)文本语言；(2)图形语言。由于图形语言开发的方便性,受到了广大工程师的欢迎，一个在计算机语言方面没有很多训练的工程师，也可在短时间内掌握虚拟仪器开发的技术，并且应用到工程实践中。虚拟仪器本质上是一个开放型的结构，由通用计算机、数字信号处理器或其它CPU 来提供信号处理、存储和显示功能，由数据采集板卡、GP IB 或VXI总线接口板进行信号的获取与控制，实现仪器的功能。根据它采用总线方式的不同，可分为以下几种类型：(1)PC总线插卡型虚拟仪器(2)并行口式虚拟仪器(3)GB IB 总线方式的虚拟仪器(4)VXI总线方式虚拟仪器(5)PXI总线方式虚拟仪器3.可
7、重构数据采集系统 我们建议的执行是使用FPGA设立一个可重构数据采集系统。该系统的操作类似可重新配置的处理器的面向捕获，同时产生和分析数字信号。这个硬件与通用的可重构虚拟仪器系统的计算机结果组合方式，最终确定用户的软件和每个特定应用所需的硬件资源。 3.1一般说明 一个数据采集系统的更重要区块如图2所示。作为一个面向应用的系统，根据不同的应用，这些模块的大部分必须是可伸缩的（增加或减少输入/输出引脚的数量）。例如，采集存储器的内存容量要根据仪器的要求来设定。同时，如果该设备提供足够的资源，一些仪器可以同时工作。在这种情况下，在图2所示的结构有些模块必须相应地成倍增加，而同时其他的模块在仪器中则
8、可以共享。例如，一个唯一的计算机接口模块复用的时间比一般时间为更有效，因为较少的输入/输出引脚致力于通信任务。 图2.一个通用的数据采集生成系统框图在计算机方面，该软件是致力于存储和数据可视化，并进行配置和对硬件的控制。第一个任务是实施应用水平，并利用多任务操作系统的优势和先进的图形界面。第二项任务主要实现了操作系统的扩展和在这方面他们通过硬件来紧密相连。图2所显示模块的简述在下一节。此外，为这些框图实现配置设备的特点（SRAM的FPGA）也进行了描述。3.2输入/输出模块 输入/输出模块符合与现实世界的接口，输入/输出模块可重构设备必须是双向的，并且具有三态功能和更快捕获率的内部寄存器。 3
9、.3采集控制块 数据采集通常是与一些外部或内部的事件同步的，这一任务是由采集控制模块开发。因此，这种控制由信号的输入/输出模块和内部逻辑的进程变得非常重要。具有低偏移和大扇出分销网络的架构是强制性的目的。 同时，一些输入和输出往往有着共同的控制信号，因此携带控制信号的一个外围总线的设备适合这种应用。3.4定时模块 这个定时模块（振荡器，定时器和计数器）为数据采集系统提供内部控制信号，特别注意计数器的设计，以达到最大的工作频率。 3.5内存模块 内存模块作为一个采集/生成数据的临时存储区域。这种内存块通过计算机接口孤立地转移数据采集的过程。因此，这些存储设备实现的功能，与拥有不同时钟频率推/弹出
10、操作双端口FIFO类似。 该内存模块可以实现如内部或外部单位的FPGA。第一种情况较为可取，因为设计提供了最佳的性能，功耗更低，而且更不容易出错。因此，拥有嵌入式双端口内存块的FPGA更适合这些目的。 3.6数据处理单元 数据处理单元执行的实时预处理的数据采集。该单元实现了更加重要的算法来确定的数据吞吐量，同时其他单元可以转达对软件的控制（在电脑端）。有详尽分析的单元，其中算法必须在硬件上实现，同时必须在软件中实现是为每一个不同的仪器。对于逻辑分析仪为例，触发模式检测逻辑必须在硬件中实现更好性能的同时，数据格式的数据转换（装配，拆卸），可以在计算机上完成。 3.7计算机接口 对于可重构的互连数
11、据采集卡与计算机，有两种不同的情况，一种是使用一个直接的扩展/本地总线连接，而另一种是使用串行/并行通信接口。在第一种情况中，可以可以得到一个拥有很大数据吞吐量的仪器，但是这种接口会消耗FPGA的很多资源（逻辑和输入/输出引脚）并且限制之间联网系统的物理距离。第二种情况中，串行/并行通信接口的限制了转移的二进制率，但消耗更少的逻辑和输入/输出资源，并允许了设备之间的物理隔离。这最后一个特点对于便携式仪器的实现来说是非常重要的，并隔离了采集硬件和嘈杂的环境通用计算机。通过这个原因，开发的系统实际上是实现了标准的IEEE - 488（ECP模式）作为与计算机的通信接口。 4.结论 几个采用赛灵思（
12、XC400E）和Altera（FLEX10K）的原型版开发了一个虚拟逻辑（国家和时间）分析仪的实现。一个超过五年的性能表现得到了使用了商业数据采集卡虚拟仪器的实现。 Virtual Instruments Based on Reconfigurable LogicAbstract. A virtual instrument results from the combination of a general purpose computer with a generic data acquisition system in order to emulate a traditional measu
13、rement instrument. The data acquisition hardware of the virtual instruments provides computers with input/output capability and is usually based on the integration of standard circuits with fixed architecture. Meanwhile the software defines the analysis and processing of the acquired data that is th
14、e function of the generated virtual instrument. As a consequence, the virtual instruments are characterized by their versatility and low cost but they lack of performance of the application oriented hardware architectures. In this paper, we present a virtual instrument system based on reconfigurable
15、 hardware that improves the features of virtual instruments preserving their versatility and low cost.1. IntroductionThe emergence of virtual instrumentation is a revolution in the history of the development of measuring instruments. It fully utilizes the latest computer technology to implement and
16、extend the instrument function. Using the image of a computer screen can be easily simulate a variety of equipment control panels to the needs expressed in the form of the output of test results. Using computer software to achieve most of the signal of the analysis and processing to complete a varie
17、ty of control and test function. The user through the application of general-purpose computer program modules and features of the hardware together. Through friendly graphical interface to operate this computer. As in operating their own definition of individual instruments of their own design can b
18、e measured to complete the acquisition, analysis, determine, control, display, data storage and so on.Virtual Instruments advantages of more traditional instruments: (1)A strong integration of computer hardware resources. Breaking the traditional instruments in data processing, display, storage and
19、other limitations, and greatly enhanced the capabilities of traditional instruments. (2)The use of computer software resources to achieve some part of the software of instrument hardware, saving material resources, increase system flexibility. Through software technology and the corresponding numeri
20、cal algorithm. Directly on the test data for various analysis and processing in time. Through the graphical user interface technology, truly user-friendly, human-computer interaction. (3)Hardware and software of virtual instrument is an open, modular, reusable and interchangeability characteristics.
21、 Therefore, the user can according to their own needs and use different manufacturers products. The development of the instrument system is more flexible, efficient and shorten the formation time of the systemThe traditional instruments are application specific systems based on fixed hardware and so
22、ftware resources so their function and applications are defined by the manufacturer. These instruments are complex systems and therefore they become expensive and difficult to manage.The widespread usage of personal computers in many scientific and technological fields make them an ideal hardware an
23、d software platform for the implementation of measurement instruments. By adding a simple data acquisition system, a personal computer can emulate any instrument. The instruments generated in this way are called virtual instruments because they do not have exclusive access to hardware and software r
24、esources. Different instruments can be implemented over the same hardware by only reprogramming the software. The virtual instruments offer plenty of advantages the most important of which is the low cost due to the reusability of hardware and software resources. The above characteristics and the co
25、ntinuous evolution and cheapening of the personal computers make the virtual instruments a valuable alternative to traditional ones.Nevertheless, there are two main factors which limits the application of virtual instruments. By one hand, the data capture is reduce to slow rates because of the more
26、common operating systems of the general purpose computers are not oriented to realtime applications. By other hand, the data acquisition system is not an application oriented system but a generic one. Therefore, our proposal is focused on the enhancement of virtual instruments by the replacement of
27、the generic hardware with a reconfigurable data acquisition system, as it is shown in Figure 1. By this way, some data process can be implemented by hardware reducing the data flow to/from the computer and rising the maximum sample rate.Fig. 1. Virtual Instruments based on reconfigurable logic.The b
28、enefits of virtual instruments based on reconfigurable logic are the following:-The bandwidth of the instruments can be increased implementing the more time critical algorithms by hardware.-The input/output capacity can be reconfigured according to the application. In special, FPGAs devices are char
29、acterized by a great number of input/output pins providing virtual instrument with the capacity to observe and control a wide number of signals.-The computer interface can be reconfigured according to the available resources (Plug&Play peripherals).-Different instruments can share software and hardw
30、are design modules increasing their reusability.2. The composition and classification of virtual instruments Virtual instrument system mainly consists of computers, hardware board,software and accessories. Users can request the flexibility to build their own testing equipment.The core of virtual ins
31、trument is software, which is mainly provided by the hardware driver, application programming software etc. It can complete all the test requirements. The current development environment mainly into two categories:(1) text language; (2) graphics language. As the graphic language developed by conveni
32、ence welcomed by the majority of engineers. There are not many trained in computer language engineers able to master the development of virtual instrument technology and applied to engineering practice in a relatively short period of time. Virtual instrument is essentially an open structure which to
33、 provide signal processing, storage and display functions by general-purpose computer, digital signal processors, or other CPU. To achieve instrument functions from data acquisition boards, GP IB or VXI bus interface board for signal acquisition and control. According to its different ways of using
34、the bus can be divided into the following types: (1) PC Bus - plug-in card-based virtual instrument(2) parallel port virtual instruments (3) the way of GB IB bus virtual machines (4) VXI bus mode Virtual Instrument (5) PXI bus mode virtual instruments3. Reconfigurable Data Acquisitions SystemsWe pro
35、pose the implementation of a reconfigurable data acquisition system using FPGAs. This system operates like a reconfigurable coprocessor oriented to the capture, generation and analysis of digital signals. The combination of this hardware with a general purpose computer results in a reconfigurable vi
36、rtual instrumentation system where the end user determines the software and hardware resources required for each particular application.3.1 General DescriptionThe more essential blocks of a data acquisition system are represented in Figure 2. As an application oriented system, most of these modules
37、must be scalable (increasing or decreasing the number of input/output pins) according to different applications. For example, the capacity of the acquisition memory varies with the requirements of the instrument.At the same time, if the device provides with enough resources, several instruments can
38、be active simultaneously. In this case, some blocks of the structure shown in Figure 2 must be multiplied accordingly while others can be shared among instruments. For example, an unique computer interface block multiplexed in time is generally more efficient because less input/output pins are dedic
39、ated to the communication tasks. Fig. 2. Block diagram of a generic data acquisition-generation system.In the computer side, the software is dedicated to the storage and visualization of data, and also to the configuration and control of the hardware. The first tasks are implemented at application l
40、evel and take advantage of multitask operating systems and their advanced graphic interfaces. The second tasks are mainly implemented as extensions of the operative systems and in this way they are closely linked to the hardware.The blocks represented in Figure 2 are briefly described in the next se
41、ctions. Also, the characteristics of the configurable devices (SRAM FPGAs) required for the implementation of these blocks are indicated.3.2 Input/Output ModulesThe input/outputs modules conform the interface with the real world. The input/output blocks of the reconfigurable device must be bidirecti
42、onal, with tri-state capability and internal registers for faster capture rates.3.3 Acquisition Control BlockThe data capture is usually synchronized with some external or internal events and this task is developed by the acquisition control module. As a consequence, the routing of this control sign
43、als to the input/output blocks and to the internal logic becomes very important. An architecture with several low skew and great fan-out distribution networks is mandatory for this purposes.At the same time, several inputs and outputs usually share common control signal so a device with a peripheral
44、 bus carrying control signals is suitable for this application.3.4 Timing BlocksThe timing blocks (oscilator, timers and counters) provides internal control signals to the data acquisition system. Special attention was dedicated to the design of counters in order to reach maximum operating frequenci
45、es.3.5 Memory BlocksThe memory blocks operate as a temporary storage of the acquired/generated data. This memory blocks isolate the data acquisition process from the transference through the computer interface. Therefore these storage devices are implemented as dual-port FIFOs with different clocks
46、for push/pop operations.The memory blocks can be implemented like internal or external units to the FPGA. The first case is more desirable because the design offers best performance, consumes less power and is less error prone. Therefore, the FPGAs with embedded dual port memory blocks are more suit
47、able for these purposes.3.6 Data Processing UnitThe data processing unit performs a real-time pre-processing of the acquired data. This unit implements the more critical algorithms that determine the data throughput while the others can relay over software control (in the computer side). An exhausti
48、ve analysis of which algorithms must be implemented in hardware and which must be implemented in software was made for each different instrument. For example in a logic analyzer, the detection logic of the trigger patterns must be implemented in hardware for better performance meanwhile the data con
49、version formats of data (assembling, disassembling) can be done in the computer.3.7 Computer InterfaceThere are two different options for the interconnection of the reconfigurable data acquisition board with the computer, one using of a direct expansion/local bus connection and the other using of a serial/parallel communications interface. In the first case