Are You Ready to Make the Transition
. . . from Traditional ICT to Hybrid Boundary Scan/ICT Testing?
Boundary scan testing (aka JTAG and 1149.1) has been hailed for several years as the savior of board-level testing in this age of shrinking geometries and skyrocketing circuit complexity. Surprisingly, actual usage of boundary scan testing by major electronics manufacturers has lagged far behind the potential. Why?
Why Boundary Scan Isn’t Used Much Yet
ACUGEN® Software’s research has identified several reasons for low utilization of boundary scan capability today:
• Bugs in BSDLs. BSDL files formally define the structure and parameters of the boundary scan support circuitry inside a device, including the length of the scan chain and order of bits in the scan chain. BSDL files are provided free (i.e., unsupported) by manufacturers of boundary scan-capable devices. Many of these BSDLs have explicit quality disclaimers in them, typically saying that the BSDLs have never been tested.
• Lack of automation in some parts of the process, particularly in customizing BSDL files for programmable logic devices.
• Few, if any, boards are built entirely with boundary scan devices. This means the board has to be put on an in-circuit board tester to test the non-boundary scan devices. Once the board is on the in-circuit tester, it is usually easier to stick with the old known testing method (in-circuit) rather than go through the painful process of learning the new (boundary scan). This "stick to the old method" is particularly appealing in today’s fast-paced, down-sized, time-to-market-critical environment, but sacrifices the major long-term benefits of moving to boundary scan.
The major in-circuit board test suppliers, plus several other companies, currently provide boundary scan test development software products. These products go a long way toward automating and simplifying boundary scan test development, but they do not solve the above problems. ACUGEN Software’s new boundary scan testing products were developed specifically to meet these needs. The ACUGEN tools also work with and complement those from other vendors.
Why It’s Worth Implementing Boundary Scan Testing
Companies that succeed in switching to boundary scan testing can achieve major savings and competitive advantages:
• By eliminating the need for in-circuit fixturing nails, circuit board densities can be increased. This allows more electronics in the same space or the same electronics in a smaller package. Many industries compete based on logic densities, e.g., hand-held communication and computing.
• Reducing the number and density of nails on in-circuit fixtures lowers costs and increases fixture reliability.
• Testing most of a board with boundary scan simplifies the requirements for testing the rest of the board, so a lower cost in-circuit or MDA system will suffice.
Making the Transition to Boundary Scan Testing
Organizations migrating from traditional bed-of-nails in-circuit testing (ICT) to boundary scan typically go through several stages. In the beginning, test engineers notice that individual large devices have boundary scan capability, and they attempt to implement single-ship boundary scan tests for these devices. Common challenges encountered at this stage are:
• The designer may have hard-wired the boundary scan control pins to power or ground.
• Lack of a low-cost single-chip boundary scan tool and insufficient experience and knowledge to make a wise purchase of a high-end, whole-board, boundary scan test generator.
• Constraints imposed by surrounding circuitry on the board often require modification to data files that drive the test generator in order to make the test work. Modifying these data files is tedious, error-prone, and requires knowledge that the typical test engineer does not have.
ACUGEN Software offers the tools and support to speed up and simplify your transition to boundary scan testing.
Check Out ACUGEN Software’s Boundary Scan Tools
ACUGEN Software, Inc. provides Automatic Test Generation solutions for user-configurable digital electronics – PLDs, FPGAs, gate arrays, boundary scan, and circuit boards – through a worldwide distribution and support network. The ACUTAPTM boundary scan tools, including PROGBSDLTM and TESTBSDLTM, were introduced in the Fall of 1996.
Contact us via email acugen att acugen.com or call 603-261-2468 or visit our web site at http://www.acugen.com for more information or for a benchmark with your own file.
Glossary
Boundary scan - test method, defined by IEEE std 1149.1, for testing electronic subassemblies, most notably circuit boards. Sometimes referred to as JTAG.
BSDL - Boundary Scan Description Language, defined in IEEE std 1149.1b, is the language for describing the boundary scan circuit elements inside a boundary scan-compliant device.
MDA - manufacturing defects analyzer, a type of low cost board tester that cannot run vectors but which can detect many of the more common board assembly defects.
ACUGEN and ATGEN are registered trademarks and ACUTAP, PROGBSDL, TESTBSDL
and MODBSDL are trademarks of ACUGEN Software, Inc.
27Jan97