JTAG AAP adds value to ICT programs
17 April 2009
JTAG Technologies’ AAP (Approved Application Provider) Blue Technology based in Reading, UK, has a long history of ATE problem-solving and customising applications to suit customer needs. When it added boundary-scan testing to its portfolio four years ago, the company sourced the technology from JTAG Technologies.
Their Commercial Manager, Graham Stallard, explains why with five years JTAG experience under their collective belts, Blue Technology can offer JTAG application development and integration services within one of the world’s most ubiquitous ICT (In-Circuit Test) systems; the GenRAD 228x and TestStation TS12x series.
The two most prevalent structural PCB test methods available today are ICT and boundary-scan (JTAG), so it seemed natural that the most powerful test solutions should combine the two techniques. However, whilst boundary-scan companies have sought to invent new uses for their side of their technology (such as the use of boundary-scan for device programming, MCM testing, pseudo function testing, and cluster testing), the traditional ICT companies have been slow to embrace the full benefits of boundary-scan. It is for this reason that JTAG Technologies in particular spent time developing independent, generic boundary-scan upgrades for a series of ICTs and Flying-Probe Test (FPT) machines. Known as the Symphony range, these upgrades now support over 10 systems from more than seven manufacturers.
Blue Technology, established in 2002, boasts three full time ATE programmers among its staff with combined experience totalling more than 75 years in the business. As boundary-scan/JTAG started to emerge as an essential element in 21st century testing, Blue invested in JTAG Technologies’ equipment and soon became part of its AAP network. In one of their most recent projects for a blue chip defence contractor, Blue Technology was tasked with making a fully integrated JTAG/ICT solution.
“The project in question is a complex assembly comprising three boards that required JTAG testing with a total of over 4000 nets and 20 JTAG devices between them,” recounts Stallard. The most complex of the boards featured approximately 2400 nets, several hundred of which could not be accessed by conventional ICT. However, thanks to the presence of nine large JTAG (IEEE std.1149) compliant devices, including seven in BGA packaging, full test coverage was still possible. On top of the ICT shorts and component checks (where possible) JTAG tests on the boards comprised the regular scan path infrastructure, pin interconnects, resistor pull-up/down checks and various memory cluster tests.
All the tests were initially developed on a bench set-up that used JTAG Technologies’ DataBlaster hardware and its Classic application developer tools. Once verified on the UUT the test was ported to the Teradyne TS 124 using the latest JTAG Symphony compiler (recently updated with co-operation from Blue Technology) that creates the test files in a format compatible with Teradyne’s DSM (Deep Serial Memory) I/O card.
“A process that was ‘pretty painless’,”adds Stallard, who also points out that the principle driver for JTAG adoption on this board and many others is: “Simply an ‘access issue’. BGA-packaged devices are almost impossible to probe directly and designers are reluctant to place test lands on every node due to fear of compromising signal integrity and because it consumes real estate. Using JTAG is the most efficient way to ensure the best possible test coverage on these types of boards.”
An additional benefit that the Blue Team can offer is a close relationship with its sister company Elite Interfaces. They provide an in-house source for most of Blue Technology’s fixture requirements. Located in the same building, Elite can provide fixtures for ICT systems and functional or ‘hot mock-up’ style testers.
JTAG testing is a great match to conventional In-Circuit Testing. If one can also use ICT hardware to apply the test pattern and interact real ICT pins with JTAG virtual ICT pins, the integration can be considered seamless.
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