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The Evolution of Test

First hard instruments

Then virtual instruments

Now embedded instruments

Softer trends

Test and measurement (T&M) is becoming softer. From the earliest days of the electronics industry, T&M has evolved from a practical reliance on external hardware testers, expanded to include hardware-specific virtual instruments and now it has advanced even further by embracing software instruments embedded in silicon – embedded instruments – that are capable of validating, testing and debugging chips, circuit boards and systems from the inside out. These new methods based on software-driven embedded instruments are unshackling T&M from the hardware limitations of the past.

A look back

To a certain extent, early advancements in T&M equipment by pioneering companies like Hewlett-Packard, Teradyne and others transformed the electronics industry. During the 1960s, demand for electronics grew rapidly, reaching a point where bottlenecks in the manufacturing process were impeding the growth of the industry. That is, manufacturing volume was hard pressed to keep pace with demand. One of the bottlenecks in the process was test.
 
In those early days, test was slow and laborious. An army of technicians using the same tools that designers had employed during development would manually test subassemblies and systems in the midst of the manufacturing flow. Soon, it was obvious that test automation would be essential to higher manufacturing volumes. The result was the creation of a new equipment category, automated test equipment (ATE).

Like the electronic systems of the day, early ATE systems were big and boxy. They were large hardware-intense
systems that automated what previously been done manually by technicians, placing a physical probe on a manufactured electronic assembly to test its functionality. Early ATE systems, the descendants of which are still in use today, removed the army of technicians from the manufacturing test process, but early ATE systems retained the basic probe-based test methods; they simply automated the process. By the early 1970s and into the 1980s, in-circuit test (ICT), which is a type of ATE test system that relies on test fixtures and placing physical probes on printed circuit boards to perform test, had become a mainstay of most high-volume electronic manufacturing lines. Test was automated, but it still depended upon the probe.
 
While ATE equipment served the industry well, the unrelenting progress of technology forced the evolution of T&M. Advanced technology was not being adequately addressed by legacy ATE testers. As a result, new T&M methods were invented.

Virtual Instruments

As the diversity of electronic products and manufacturing volumes increased in the 1980s, the limitations of hardware test equipment became more apparent. Hardware test systems were and still are hard-wired to a few specific functions and to a narrow range of measurements. A new product based on advanced technology often required that the manufacturer procure another hardware test system compatible with new technology. Regularly replacing hardware test systems inflated the cost of test while manufacturers were trying to drive down the cost of their products to stimulate greater demand in the marketplace. The concept of virtual instruments was a response to this situation.
The notion of virtual instruments is an attempt to move a portion of the test process from limited-function hardware test systems to software-based test methods. Virtual instruments are still closely coupled with certain hardware test modules, but, because virtual instruments are mostly software, test methods based on them could be more adaptable to changes in technology and advancements in the manufacturing process. Functioning in concert with smaller, less expensive modular hardware instruments instead of legacy ‘big-box’ATE hardware testers added to the flexibility and adaptability of virtual instruments. In addition, graphical programming environments, such as National Instruments’ LabVIEW™, allowed virtual instruments and their complementary hardware modules to be effectively configured into effective test and measurement systems.

Embedded Instruments

During the mid-to-late 1990s, basic technology advancements like new chip packaging technologies, circuit board design techniques and higher-speed, more electrically sensitive input/output (I/O) buses connecting chips on circuit boards caused problems for legacy ATE systems and hardware-limited test methods in general. Specifically, access for physically probing chips and boards was disappearing. Pins on chips, which previously could be probed for test purposes, were suddenly hidden beneath the silicon in chip-scale packages like ball grid arrays (BGA). Another example of vanishing access for probe-based systems like ICT testers was the rapid disappearance of test pads on circuit boards. To add functionality to electronic systems, boards were densely populated with chips, leaving little or no room for test pads at all. Moreover, high-speed I/O buses were becoming so sensitive to the capacitive coupling effects and reflections induced by test pads that many new board designs banished pads completely.
 
Fortunately, while the progress of technology was dictating another step in the evolution of T&M, certain test technologies and methods were emerging that would enable the application of   instrumentation embedded in semiconductors in non-intrusive T&M technologies. Chief among these technologies was boundary scan (IEEE 1149.1) or what is often referred to as JTAG after the Joint Test Action Committee which initiated development of the standard. A software-driven technology, boundary scan provides non-intrusive probe-less access to embedded instruments in
chips that have been soldered onto circuit boards. A simple connector on the board links the embedded test resources in chips and on circuit boards to a software test system such as the ASSET ScanWorks platform for embedded instruments running on a personal computer. The only hardware required is a controller card in the PC and an interface pod between the PC and the board-under-test. This type of non-intrusive methodology frees test equipment completely from the limitations of physically probing chips and circuit boards, as well as hardware test modules. As a software-driven test methodology, it is very flexible and adaptable. Consequently, the test system’s software can change right along with advancements in basic electronic technology or alterations to the manufacturing flow.  
 
Throughout the 1990s and the first decade of the new century, additional industry standards to facilitate non-intrusive test methods were developed and adopted. Moreover, chip suppliers and system manufacturers began to realize how valuable embedded instruments could be. Initially, chip suppliers inserted embedded instruments to facilitate chip test and characterization, but the industry realized that these same instruments could be applied to a range of test applications, such as prototype board bring-up, manufacturing test of circuit boards and troubleshooting in the field.

The Future is Now

Of course, electronic technology will continue to advance and T&M will evolve right along with it. Chips will get smaller and new packages, like stacking multiple die in the same carrier, will only limit further the effectiveness of test equipment that relies on any sort of a physical probe. High-speed buses and chip interconnects will only get faster, making them more sensitive to probing and narrowing the means of validating their signal integrity. And circuit board design and fabrication techniques will continue their current course toward greater complexity, many-layered boards and other techniques that simply defy physical probes.
Simultaneous with progress in base electronic technology will be advancements in T&M based on embedded instruments. New standards like the IEEE P1687 Internal JTAG (IJTAG) standard for embedded instruments and the IEEE P1838 standard concerning test methods for 3D chips are already emerging. These specifications and others point out that T&M is evolving to non-intrusive, software-oriented validation, test and debug methods based on embedded instruments.

ScanWorks® Platform for Embedded Instruments

The ScanWorks platform for embedded instruments is at the vortex of the swirling forces at work in the T&M industry. At a time when the effectiveness of traditional legacy T&M equipment is rapidly diminishing, the ScanWorks platform capitalizes on the non-intrusive test standards and technologies developed over the last 15 to 20 years and incorporates emerging new techniques like IJTAG and others to give system and subassembly designers, manufacturing test engineers and others a clear path to the future of advanced, software-driven test technologies.
 
 

CPU & FPGA Support

ScanWorks supports Intel®, ARM®, Freescale™,
& other CPUs; Altera® and Xilinx® FPGAs.

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