Designing And Implementing A Boundary Scan Tester With USB Interface

Currently, the digital system is composed of a large amount of highly fine packeted ICs, such as PGAs, BGAs, SMTs, and MCMs. It could lead to the narrower space between the connections on the PCB and the closer distance between the test points, and it could even make some test points inaccessible. So, the traditional test methods based on probes or nails beds are no longer available. As a design for test technology, the boundary-scan test fixes a special element called boundary-scan cell (BSC) between the device input pins and the core logic inputs, or between the core logic outputs and the device output pins. Thus, the BSC acts as the virtual test probe that carries out the test stimulus, and captures the test respondences. So, when the digital system is completely made up of the boundary- scan devices, the testability of the system would be improved greatly and test problem we are confronted with would be settled easily.For this purpose, we should employ the new test instrument fit for boundary-scan test. So, I developed a boundary-scan tester with the USB interface in this dissertation. Users can set the test instructions or test vectors by the tester software. Then the tester applies the test instructions or test vectors to the circuit under test (CUT). Last, the tester receives the test respondence from the CUT and sends back to the tester software running on the PC.The design can be divided into the following parts:â‘  Hardware design for the boundary-scan tester.â‘¡ Firmware design for the boundary-scan tester.â‘¢ USB driver design for the boundary-scan tester.â‘£ Application software design for the boundary-scan tester.The design result indicates that the whole test system works smoothly. Benefitted from the USB interface, the tester has the following advanced characteristics:â‘  Ability for PnP.â‘¡ Bus powered characteristics.â‘¢ Completely external attachment to the PC, without fear of the EMI, the unreliable physical attachment to the PC, and the unpredictable crash of the PC for overheating.