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Evaluating Platforms for Performance and Reusability

3.2 Reuse Existing Equipment by Building Hybrid Test Systems

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�Big Iron� ATETraditional

GPIB-Based ATE User-Defined ATE

Instrument ona Card

Evolution of Automated Test Platforms

Proprietary Tester Stand Alone VXI PC/PXI

The introduction of new platforms for test and measurement has been steady in recent history. Many of these platforms remain popular today, some cater to particular applications, while others are utilized for many applications. You can see the development from the big iron ATE to GPIB-based ATE, and then to instrument on a card with VXI. With PC/PXI you have the ability to define you own ATE.

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Issues for System Developers

System developers face challenge of how to manage and balance� Need to maximize their investment in hardware and

software� Concerns about obsolescence and longevity� How to handle maintenance and upgrades � Desire to integrate latest technologies in their system

With these evolving test platforms, system developers face various challenges and how to balance them. Since developers need to maximize their investment in hardware and software, it is not always possible to just upgrade your whole system to a newer bus technology. As a result, developers face the challenge of maintaining longevity in their systems and fighting obsolescence as well as streamlining maintenance and upgrades. While trying to maximize your system longevity is important, developers still want to take advantage of the latest technologies and integrate them into their system where possible. This availability of various platforms, both new and old, can force test engineers to utilize existing test equipment with newer equipment that may be offered with different platforms.

Hybrid test systems provide developers the ability to balance these varying needs.

Test equipment manufacturers offer various solutions to combine multiple platforms into hybrid automated test systems so that developers can maximize use of their existing test equipment.

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Hybrid ATE Systems Overview� Hybrid systems combine components from multiple ATE

platforms� Streamline system transition and maintenance� Protect investment in existing software and hardware� Allow easy integration of advances in ATE system development

� Layered architecture is important� Multiple entry points

� Multiple hybrid topologies are available

Hybrid ATE systems provide developers with a long-term ATE system that can evolve with short commercial technology lifecycles. Hybrid ATE systems take advantage of a five layer architecture to increase reusability, connectivity, extensibility, and module replacement.

By following the layered architecture, you create a test framework that allows you to replace and/or add components without having to re-architect the whole system. By layering your test system, you create multiple entry points so that changing components is simpler. By clearly defining the system, you can take advantage of multiple buses using a variety of hybrid topologies. This allows you to meet multiple needs—protect the investment in existing hardware and software while being able to integrate the latest technologies.

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Layered Architecture for Automated Test SystemsTest Management Software � Interchangeable Test SequenceTest Programs� Modular Test Steps/Modules

Flexible Device Drivers and Instrument Libraries� Plug&Play and IVI Drivers� VISA Common API� Configuration Utilities and Files� Switch ExecutiveTest Hardware Platforms and Devices

Selecting the measurement I/O platform that best suits your needs is a crucial step when architecting a system. Often times test engineers can benefit from combining existing measurement hardware with newer hardware devices. Fortunately, there are a variety of options available today for building hybrid systems which consist of combining multiple hardware platforms into one heterogeneous system. The platform layer allows you to account for instrument connectivity needs (connecting instruments of multiple platforms) so that you can connect to legacy or specialized instruments and reuse ATE components.

An integral part of your test system is the flexible device drivers that act as the bridge between hardware to software. These drivers are critical to the overall test system, as they simplify configuration and integration of your hardware with the test code that executes functional tests.

Building on top of the device drivers and instrument libraries, you can create reusable, modular test programs. Instead of creating test code with all system-level and UUT-level tasks, break out the individual steps in your test program into test modules.

Then use the test management software as a test framework to build your test sequences using the test programs. Here, using TestStand, you can manage the control execution flow of your test code, automate test programs written in any language, manage user interfaces for the various users of your test system, and quicken development time by taking advantage of the reusable test modules.

Not only is the system topology important, the software framework heavily impacts your ability to make a modular, flexible test system. The software framework is composed of the top three layers—the measurement and control services (drivers and configuration manager), the application development environments in which the test programs are written in, and test management software which automates these test programs.

Plan for needs to change the hardware (replacement or upgrade) with the design of the software framework. The device drivers used and test management software should simplify the process of replacing the instrument. The drivers should simplify any programming and possibly support interchanging instruments while the test management software just calls a different test program.

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Designing Hybrid Systems� Platform Independence

� Software independent from hardware

� Industry standard interfaces� Longevity

� Reuse/replace at interfaces� Adaptable components

� Growth� Multiple entry points � Layers promote innovation and

competition� Price/Performance

� Leverage PC and COTS� Large board area in small package

Benefits of the five layer architecture

• Platform independence—Layered approach separates hardware and software. When you need to replace, upgrade, or add hardware components, rewriting all of the software is not required. Instead, create new test programs and add them to the overall test sequence. This also allows you to take advantage of standard interfaces as needed.

• Longevity—This architecture gives you a flexible system so that replacing the components can be simpler – only affects the modules that you want to change. In addition, this architecture allows you to connect new equipment with legacy or specialized instruments and reuse ATE components.

• Growth—With layers there are multiple ways that you can add to the system. For instance the user could add PXI components as opposed to VXI when needing to expand the functionality to the system. Doing this would not require rewriting the system. The platform layer allows you to account for instrument connectivity needs so that you can connect to legacy or specialized instruments and reuse ATE components.

• Price/Performance—Customer can find the right mix of price and performance. This allows customers to reuse some of their older modules that they want to preserve their investment in but also add newer components that offer a better price or performance.

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ATE Connectivity Options

EthernetEthernet-to-PXI or VXIGPIB,USB, Ethernet , Serial

PC to Stand-Alone Instrument

MXI-4VXI-to-PXI1

MXI-2, USBPCI/PXI-to-VXI

MXI-4PCI-to-PXI

PXI, VXIEmbedded Control

Bus TypeControl Interface

�Many connectivity options�Try to stay simple and modular

1Requires VXIpc with built-in PCI expansion slot

When designing the system, developers can take advantage of a variety of options to connect platforms. There are many ways to connect to both PXI and VXI chassis. Some of the more popular tools available include MXI-2, USB, Ethernet, GPIB, and MXI-4 solutions. MXI is a multisystem extensions instrumentation bus that allows you to expand both your VXI and PXI chassis.

When designing your topology, you should choose a bus to be the center (most likely use embedded controller). From there you can connect to other buses using one of the many connectivity options listed. In addition, many of the controller options provide built-in GPIB connectivity or you can use the GPIB-USB/HS.

Here are two example topologies.

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Example Hybrid System: PC Control of PXI, VXI, and GPIB

PXI

VXI

Desktop orRack-Mount PC

MXI-4 (copper or fiber-optic) or Ethernet Link to PXI System Controller

MXI-2, USB, GPIB, or Ethernet Link to VXI Slot 0 Controller

VXI Slot 0 Controller Options:VXI-MXI-2, VXI-USB, GPIB, or VXIpc Embedded Controller (for Ethernet)

PXI System Controller Options:PXI-MXI-4 or PXI Embedded Controller (for Ethernet)Stand Alone

GPIB

A simple topology uses a PC to control all of your instrumentation. In this situation, you can connect to a PXI chassis with MXI-4, which provides a transparent extension of the PCI bus, or you could use Ethernet to connect to an embedded PXI controller. Using a PCI-GPIB card you can connect to any GPIB instruments. As for the VXI connection, you could use MXI-2, USB, Ethernet, or GPIB to connect to the chassis.

If you use MXI interfaces and Ethernet to connect to the chassis, you can easily improve computer performance without having to change the rest of your test system.

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Example Hybrid System: PXI Control of VXI and GPIB

VXI

VXI Slot 0 Controller Options:VXI-MXI-2, GPIB or VXIpc Embedded Controller

PXI

MXI-2, USB 2.0, GPIB, or ENET Link

PXI System Controller:PXI Embedded Controller

Install MXI-2, USB 2.0, GPIB, or ENET Peripherals in PXI chassis

Stand AloneGPIB or

ENET Link

Another system topology you could use centers the system with PXI. This topology is good for a system in which you are adding a VXI chassis or GPIB instrument to an existing PXI system to meet unique requirements or when expanding or transitioning a VXI or GPIB-based system to PXI technology.

Benefits of using PXI as a system core include:

• Leverages PC based technology on a rugged platform that can support manufacturing long life

• Continues to offer new products, allowing for easy system expansion

• Multiple options for connectivity to other platforms

Ideally, you should try to keep PCI or PXI in the center. PCI and PXI provide many peripheral connections as well as many instrumentation connectivity options. In addition you have low latency with PCI/PXI, and PXI includes timing and synchronization capabilities. PXI is also advantageous because it offers many options for connectivity to other ATE buses:

• GPIB, Ethernet, Serial, USB built into the controller

• VXI, Gigabit Ethernet easily available

• Other buses can use Remote VISA for messaging

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Hybrid Test Systems Summary� Use the five layer architecture

� Allows reuse of components� Carefully select or build new components

� Keep PCI and PXI in the center� Best PC connectivity� Best instrumentation connectivity

� Streamlines system transition and maintenance

� Maximizes return on investment in existing software and hardware

PASS FAIL

DUT DUT DUT DUT

Hybrid systems provide developers with a way to balance their needs for maximizing investment in ATE equipment, managing longevity and obsolescence, streamlining maintenance and integrating the latest technologies. By building your system with this five layer architecture you are able to separate hardware from software making reuse of components as well as replacement or adding of new components easier. By keeping PCI and PXI in the center, you benefit from the best PC connectivity with many peripheral connections and the ability to take advantage of price/performance options. PCI/PXI also provide multiple ways to connect to other instrumentation buses.