The Research Of The SWD Agreement And The Design Of Program Downloader Based On ARM

Along with the advantages of the high performance, high code density and small wafer area which designed by ARM Inc, Cortex-M3has become the ideal platform for low cost single chip microcomputer, automobile electronic, data communication, industrial control and consumer products. The ARM processor generally uses JTAG debugging interface, because the debugging tool is cheap and convenient for development. But JTAG debugging interface takes up at least5or6pins of the chip, this is inconvenient for most single chips. But Cortex-M3also supports serial debugging based on original JTAG debugging. The SWD only takes two pins of the chip and can be carried out all of the simulation and debugging, it can save the debugging with pins.Now in the market, JLINK from SEGGER Inc, ULINK from KEIL Inc and STLINK from ST Inc all support SWD interface, but the foreign companies are not fully open the material of SWD agreement. So, there exist difficulties to develop SWD agreement in the domestic. This article focuses on the overall structure of Cortex-M3, SPI interface and communicating protocols, SWD agreement and STM32flxx chips on embedded platform. Through the four modules realize the SWD writing system:SWD agreement realizing module, target board bootloader module, SPI communication module. Finally, the article realizes the development’s integrity and reliability through the alignment and validation test system.