arm嵌入式bootloader启动过程详解（Arm embedded bootloader startup process details）.doc

arm嵌入式bootloader启动过程详解（Arm embedded bootloader startup process details） ARM embedded system Bootloader 1. Introduction: For PC, the boot after the initialization of the processor configuration, hardware initialization operation is performed by the BIOS (Basic Input/Output System), but for embedded System, for the sake of economy, the price is generally not configure the BIOS, so we must finish the work to write program, which is needed to boot program. In embedded systems, usually does not like the BIOS firmware program, started to complete initialization of this code is called the Bootloader program, so the load of the whole system to start the task is accomplished by the Bootloader. Say simply, through this program, you can initialize the hardware equipment, establish a memory map (or no memory mapping functions such as S3C44B0 CPU), and the system hardware and software environment is set in a suitable condition, so as to eventually invoke the operating system kernel, ready to run an application program the right environment. Bootloader depends on the actual hardware and application environment, so its very difficult to build a generic, standard Bootloader for embedded systems. Bootloader also depends on the configuration of embedded board level equipment, that is to say, for two different embedded motherboard, even though they are based on the same CPU and build, to run on a board Bootloader program can also run on another board, usually need to modify the Bootloader source program. Second. Start the process After the system has been reset, almost all the cpus are taken from the reset address. For example, the CPU based on the ARM7TDMI kernel usually takes its first instruction from address 0when it is reset. Embedded systems with microprocessor-based cores usually have certain types of solid-state storage devices (such as EEPROM, FLASH, etc.) mapped to this pre-set address. Therefore, after the system is reset, the processor will first execute the prog