While a number of microcontroller vendors have introduced emulation tools using the Universal Serial Bus (USB) stick form factor, what makes the $20 eZ430 tool unique is the unique 2-wire JTAG protocol the company’s engineers have incorporated into the design.

Previously in MSP430 MCU products, said Mark Buccini, MSP430 worldwide marketing and applications manager, the typical JTAG debug interface used either 4 or 5 device pins depending on the product family. In order to save on device pins, the previous lower pin-count devices have often used multiplexing of this interface with functional pins. Although this reduces pin-count, it does not allow the functional pins to be available during debug or emulation.

“In higher pin count processor architectures, the use of four or five pins for the debug function is not a big thing,” he said, “but in an eight MCU design, where you are starved for pins, reducing the pins for debug to just two can have a significant impact of the flexibility and capabilities of the final design.”

The improved JTAG interface module allows a two-wire communication called SPY bi-wire function. Despite the fact that it uses only two pins, the new JTAG module is compatible with other four or five pin JTAG modules with debug commands capable of being used like breakpoint commands and program single stepping.

Via this interface, only two signals – power and ground – are needed to connect the emulation interface and target, enabling very compact, high-performance MCU development in a low-cost environment.

Via the bi-wire JTAG scheme, the eZ430-F2013 tool connects to a standard PC USB port and is immediately ready for the developer to begin development on any of a number of TI microcontrollers for which it has been designed.

Self-powered, requiring no extra cables or power supplies, contained within the USB stick is an emulation interface board and a removable MSP430F2013 target board, which differentiates the eZ430 from other fixed-function evaluation systems.

The fingernail-sized emulation board communicates with the MSP430 MCU target devices’ emulation logic non-obtrusively, in-system and subject to the exact same electrical characteristics as the final application.

The miniscule board uses a TI TUSB3410 for the USB interface and a TPS77301 to provide 3V regulation to the system. The target board makes all 14 MSP430F2013 pins available on an industry standard 0.1 inch though-hole header and includes an LED for immediate development feedback.