Design And Realize The JTAG Debugging Module On MCU

Embedded micro control unit (MCU) which integrates CPU, communication interfaces,analog-to-digital, digital-to-analog, memory and other peripherals, has gradually developedinto system-on-chip (SOC), and simplify the application system design. These technologiesenable the computer technology from the universal and large-scale computing field into theminiature and intelligent field, expanding the range of computer technology.System hardware and software debugging is an important part in the developmentprocess of embedded systems. An efficient and powerful debugging system can greatlyshorten the development cycle and enhance the competitiveness of products.In the embeddedappliation system, how to use controlled debugging tools to achieve internal testing andmonitoring has been a hard nut to crack. At present, online debugging techniques based onJTAG protocol (IEEE Standard1149.1-TEST Access Port and Boundary-Scan Architecture) isthe most effective way for debugging embedded applications.The debug structure and module which meet the JTAG protocol in the MCU chip canstart and stop the target CPU, set the program counter, read/write memory, fast read/writememory, set hardware breakpoints, and erase the FLASH, programming online,etc. Thesedebugging operations greatly facilitate users to develop application system with MCU.Typically, the downloading of embedded MCU programs, the reading and writing of theon-chip memory are all performed through the JTAG interface. But the JTAG interface ispoorer security, any controller which match the JTAG protocol can readout the program code.In this paper, based on16-bit low-power microcontroller (MCU), architecture with JTAG fuseintegrated on chip is designed. Application engineer can blow JTAG fuse after softwareprogramming, so that unauthorized access is prohibited, illegal users can not readout thecontents of the memory, thus protect developers intellectual property. Part of the JTAG pinswere designed with multiple functions,the saved pins can be used for peripherals to enrich thefunctionality of the product, or reduce the package volume, achieving miniaturization, low cost. The JTAG module presented in the paper has been verified with a0.25um CMOSprocess, and the layout has also been completed and realized as well.