S3C2440 nand sdram startup code running transfer process

During reset, the S3C2440 Nand Flash controller obtains information through the status of the pins connected to the NAND Flash (NCON, GPG13, GPG14, GPG15). After power-on or system reset, the NAND Flash controller automatically downloads the 4K boot loader code, and after the downloaded boot loader code begins execution in the setupstone.

The boot code of S3C2440 can be executed in the external nand flash memory. In order to support the boot of nand flash, S3C2440 has an internal SDRAM cache called "Steppingstone". When booting, the first 4kbyte of Nand Flash will be imported into Steppingstone and start to execute. (****This stepstone can be understood in this way, because nand flash cannot be run directly, so it can only automatically copy the code to RAM first, and then execute it. This bootload is like this, mapped to GCS0 address, and can run into RAM after running)

Generally speaking, this bootcode will copy the Nand Flash content to SDRAM, and use the hardware ECC checksum to verify whether the Nand FLash data is legal. Once the copy is completed, the main program can execute the program in SDRAM. (Here you can check the relocate reentry code in Start.S. First, compare the instruction address, whether it is in flash=0x00000000, or sdram=TXET_BASE, then copy, relocate, and start executing from SDRAM. It doesn’t matter if you don’t understand it - if you can find the comments of Start.S on the Internet, there are a lot of content about this part, so learn more)