High-speed integrated circuit testing with jtag

摘要

The use of the JTAG port provides for boundary scan testing of integrated circuits, thereby allowing for the testing of IC's after they have been mounted into a circuit board. However, the conventional JTAG scheme is limited as to speed, since both the input and output vectors must be serially shifted in and out of I/O buffers along the chip boundaries. The present invention speeds the testing of high-speed core logic circuitry by transferring the test program to a special test data register (TDR 11), which downloads the program to the logic circuitry under test, and uploads the results. This allows the core logic to perform the test at its normal operating speed, while still retaining compatibility with the JTAG standard for other tests.