【正文】 is a driver to debug work card [2]. The boot loader of Windows CE has 3 functions. Its executable sequence is shown as Figure 3: 1) Initialization hardware: include initialization memory, interrupt controller, clock and MMU etc. 2) Control startup: the boot loader usually provides a simple alternate menu for user, letting the user choice startup process. 3) Download and execute OS image. At first, after system is electrified, the boot loader usually does code relocation. The boot loader will make itself move from a place to another place to carry out a more convenient accessing in this step. Then, the boot loader configures memory to implement the boot loader. Immediately, after setting environment variables for executing C code, the boot loader jumps to start implementing the main function. After that, the boot loader initializes debug ports and other devices. Making debug ports used as early as possible can help debug boot loader itself too. Then the boot loader implements selfcheck, if selfcheck passes, OS image will be downloaded. At last, system starts to execute OS image[2]. . Nboot Just described in hardware platform, this system includes a NAND flash which is used to store the program, and S3C2410X supports NAND flash boot loader, in that case, NAND flash boot loader is adopted in this design. When booting, the first 4KBytes of the NAND flash memory will be loaded into Steppingstone and the boot code loaded into Steppingstone will be executed. The NAND flash boot loader is called as Nboot. Nboot initializes processor and NAND flash, pletes ARM startup process, calls Eboot program. Normally when a system is electrified or reset, its processor should be initialized。 Windows CE 是一個(gè)很好的實(shí)時(shí)操作系統(tǒng)，它將會在無線通信、工業(yè)控制和消費(fèi)電子產(chǎn)品等領(lǐng)域占有更大的 市場份額。在靜態(tài) 方面， 啟動(dòng)加載器 是由 BLCommon、 OEM 代碼、 Eboot、內(nèi)存管理器和EDBG 驅(qū)動(dòng)等組成，如例圖 2 所示。最后系統(tǒng)將會執(zhí)行操作OS映像。 Startup( )函數(shù)初始化 CPU和其他內(nèi)部邏輯設(shè)備。此函數(shù)是BLCommon 庫所調(diào)用的最后一個(gè)函數(shù)，并負(fù)責(zé)跳躍和啟動(dòng)運(yùn)行時(shí)映像。通常 BLCommon 調(diào)用 OEM的可選功能，關(guān)鍵是初始化狀態(tài)是空的，如果可選 OEM功能調(diào)用，這一點(diǎn)應(yīng)當(dāng)被評估。 結(jié)論 在這個(gè)設(shè)計(jì)中，串行端口用 DNW軟件調(diào)試啟動(dòng)加載器，就像圖 6所示，啟動(dòng)加載器配置從串行端口輸出。 （ 1） 源文件：源文件是一個(gè)文本文件，它是在子目錄里為源代碼設(shè)置宏觀定義。 啟動(dòng)加載器的實(shí)現(xiàn) 啟動(dòng)加載器是由微軟提供的 Eboot、 OEM 函數(shù)庫所組成。 (4) OEMPreDownLoad： OEMPreDownLoad（）是在下載一個(gè)運(yùn)行時(shí)間映像之前被 BLCommon 所調(diào)用的函數(shù)。在 ARM構(gòu)架中定義了 7個(gè)中斷，他們是 Reset， Undefined， SWI,Prefect， Abort， IRQ，和 FIQ。 緊接著，設(shè)置環(huán)境變量以執(zhí)行 C代碼，啟動(dòng)加載器跳躍執(zhí)行主要功能。微處理器通過測試結(jié)果電流與目標(biāo)電流的對比控制汽車。通過實(shí)驗(yàn)證實(shí)，操控者可以通過視頻監(jiān)控系統(tǒng)成功的啟動(dòng) 啟動(dòng)加載器 ，視頻監(jiān)控系統(tǒng)可以幫助調(diào)試系統(tǒng)，下載操作系統(tǒng)圖像。 the task is performed by boot loader. This part of the boot loader is written in assembly language. Some detail of boot loader which is needed to be pay attention is shown as follow: 1) Write the boot loader in assembly language 2) Disable the interrupt 3) Put the CPU into the supervisor mode 4) Put the exception vector list in the start position of image So does the ARM processor. In the beginning, ARM processor must be initialized, its processes are shown as follow: 1) Set the entry point 2) Configure the exception vector list 3) Disable the watch dog 4) Disable the interrupt 5) Configure PPL 6) Close MMU/MPU 7) Initialize the storage 8) Copy the RW data section 9) Clear the ZI data section 10) Initialize the stack point 11) Start the interrupt system 12) Set the CPU model 13) Jump to main( ) function Setting the entry point is the first task that should be perform, each image has only one entry point. Usually it is marked with ENTRY. As the exception happens, the program jump to the exception vector list, and then switch to a corresponded function. The exception vector list should be placed in 8*4 byte space of memory. There are seven interruptions defined in ARM architecture, they are Reset, Undefined, SWI, Prefect, Abort, IRQ, and FIQ. If the starting address of the RAM is 0 when the system is running, the exception vector list should be rebuilt. And if the interrupt is not be used, the function should point to a loop for avoiding the confusion which is caused by the false interrupt. Considering the ARM startup process, the designed Nboot process is shown as Figure 4: The main( ) function that the Nboot calls lastly should perform these tasks: 1) Enable the MMU 2) Initialize the serial port 3) Output the serial port information 4) Initialize NAND flash 5) Read Eboot from NAND flash 6) Load the Eboot . Eboot The first function called by Eboot is Startup( ), then Startup( ) calls the Bootloadermian( ) to perform most of the tasks. It’s executable flow is shown as Figure 5: After system is electrified, the first Eboot function implemented is Startup( ), this function is edited in assembly language, locating on the . The Startup( ) function initializes CPU and other kernel logical devices. The tasks that the Startup( ) function needs to perform may vary depending on the hardware, but in general, the Startup( ) function perform the tasks as follows [3]: 1) Set CPU in supervisor mode, in this mode memory and hardware can be accessed without limits 2) Shield CPU against all interruptions 3) Close