Design and Implementation of a Single-Chip ARM-Based USB Interface JTAG Emulator

Boundary-scan technology is a popular design-for-test technology, which is used by some embedded chips by means of embedding special boundary scan cells inside the circuits. It allows the debugger to talk via a JTAG port directly to the IC´s core. As more and more chips using the JTAG interface, the application of JTAG emulator becomes frequent. Commercial JTAG emulators using parallel port on the market are usually expensive and inconvenience. This paper describes two methods to design an inexpensive USB interface JTAG emulator based on a single-chip ARM, including theirs hardware and software. One is the GPIO pins of an ARM device are used to generate TAP timing and its USB port is used to communicate with PC. Another is used the SPI interface to generate higher TCK. Result shows that this emulator not only has high speed but also is portable.