JTAG functional test

ScanExpress JET from Corelis is an unusual new test tool which combines boundary-scan and functional test technologies to achieve higher test coverage. JTAG Emulation Test (JET) combines common pin and net level diagnostics using boundary-scan testing with functional tests running on the target board's embedded microcontroller accessed via the JTAG debug port. This provides functional test capabilities on designs utilizing JTAG compatible CPUs to even non-JTAG peripheral components including analog parts connected within the CPU address and I/O space. This means that sound structural tests for opens and shorts can be performed via boundary-scan while at-speed functional testing can be performed using the CPU to run test programs loaded into memory. Before loading test programs into on-board memory, ScanExpress JET is using a proprietary technique to test the on-board memory at speed without loading any code into this memory. This means that ScanExpress JET can test and diagnose faulty boards and systems even when the embedded CPU is not able to boot and the board self test is not operational.

ScanExpress JET carries existing boundary-scan testing to the next level. Because no single test technology offers 100% test coverage, test engineers are constantly looking at ways to combine the strengths of each test methodology and maximize the overall testability of their products. ScanExpress JET now offers a feasible way to close the gap between boundary-scan testing and functional testing. Utilizing a single software and hardware tool to combine the two technologies reduces test integration time yet still provides greater test coverage.

Users can access pre-built functional tests or create functional test scripts from scratch to test non-standard parts. Furthermore, because ScanExpress JET seamlessly integrates with existing Corelis hardware, existing ScanExpressTPG, and ScanExpress Runner customers can add-on this functionality without having to purchase an additional JTAG controller to access the embedded CPU. Corelis multi-TAP controllers can provide emulation and debug capability on one TAP while connecting the rest of the boundary-scan chain on separate TAPs. No other test tool currently allows this configuration. Performing all of the testing from a single JTAG controller not only reduces cost, but also simplifies the hardware required for testing and the connection to the product under test.

ScanExpress JET takes advantage of the fact that most of the 32-bit and 64-bit processors have a built-in JTAG emulation debug port, using the JTAG debug port to control the CPU and perform functional tests.

For further information, see our Corelis pages