Using the STA400 chip (the industry’s first ever mixed-signal IC fully supporting the IEEE Standard 1149.4 mixed-signal test bus) jointly developed by LogicVision and National Semiconductor, a company in the U.S. was successful in testing an evaluation board typically containing both analog and digital circuitry, utilizing its intranet to control a test system located remotely. Engineers were able to distantly probe the test board in real-time using an on-line schematic diagram of the object, measuring voltages at component pins. With smaller, denser boards, test access has been compromised, and fault detection and diagnosis is limited. Digital portions of boards presently benefit from extensive use of the familiar IEEE 1149.1 boundary-scan standard for automated test generation and board test. To access analog test points, however, an in-circuit tester (ICT) must be utilized, and the board layout and shielding must allow probing. However, the IEEE 1149.4 mixed-signal test bus reduces the need for ICT, allowing for denser board layouts, and “silicon nails” can also access analog test points. Both companies have been working together to develop and promote test technology based on the 1149.4 standard. With the capability of the STA400 device, electrical test is re- portedly now possible at the analog nodes that previously could not be accessed without time-consuming custom design. (gbw)
