Bootloader Series II -- ARM920T -- bootloader architecture design

Reprinted from ：https://www.cnblogs.com/china-sdd/p/6171447.html

I will introduce the following chapters according to this framework ---- Reprint note

The complete code will be uploaded in the last blog in this series .---- Reprint note

2440 ARM Processor startup process ： from nand flash Mode start , The processor will be front-end 4k Copy the contents of to SRAM(stepping stone) in , Greater than 4k Copy the contents of to memory .

bootloader Divided into two stages ：

BL1：

1. Core initialization
   1. Set the exception vector table
   2. Set the processor to svc Pattern
   3. Turn off the watchdog
   4. Turn off all interrupts
   5. close mmu and cache
2. C Language programming environment settings
   1. Set the stack
   2. clear bss paragraph
3. LED initialization
4. Initialize the system clock
5. Memory initialization
6. Copy nand flash Medium BL2 Into memory
   1. Simple initialization nand flash
   2. Copy code to memory
   3. Jump to the second stage entrance

BL2：

1. mmu initialization
2. Interrupt initialization
   1. Interrupt initialization
   2. Key initialization
3. Initialize serial port
   1. Serial initialization
   2. transplant printf function
4. Network card initialization
5. LCD initialization
   1. Initialization of touch screen
   2. LCD initialization
6. Parse and execute user commands
   1. transplant tftp command
   2. transplant bootm command