MobileRead Forums - View Single Post - Is Das U-Boot on the MMC or some other type of ROM?

asymptote · 11-02-2012, 01:17 AM

Thank you hawhill, that was the answer I was looking for -- that Das U-Boot is indeed stored on the MMC and can be dumped, overwritten, and restored.

My next question is this: is the MMC at least partially (perhaps not all 4gb) memory mapped into a range of addresses? If so, what are these addresses and does the ROM need to be aware of this if it uses absolute memory offsets? What is the code execution entry point in the ROM and in memory?

I want to know the structure of the ROM and how it is loaded and executed, so I can jump into writing a custom bootloader. The bootloader would do some serial IO and nothing more, I think that the next step might be to figure out how to cross compile Das U-Boot and once I get flashing my custom U-Boot ROM working I'd work on modifying it's source code and trimming it down to the point where it only did serial IO that way I'd always have something that was working.

Do you have any suggestions or information about the boot process?

Thanks!

11-02-2012, 01:17 AM	#14
asymptote Junior Member Posts: 3 Karma: 1000 Join Date: Oct 2012 Device: Kindle 3	Thank you hawhill, that was the answer I was looking for -- that Das U-Boot is indeed stored on the MMC and can be dumped, overwritten, and restored. My next question is this: is the MMC at least partially (perhaps not all 4gb) memory mapped into a range of addresses? If so, what are these addresses and does the ROM need to be aware of this if it uses absolute memory offsets? What is the code execution entry point in the ROM and in memory? I want to know the structure of the ROM and how it is loaded and executed, so I can jump into writing a custom bootloader. The bootloader would do some serial IO and nothing more, I think that the next step might be to figure out how to cross compile Das U-Boot and once I get flashing my custom U-Boot ROM working I'd work on modifying it's source code and trimming it down to the point where it only did serial IO that way I'd always have something that was working. Do you have any suggestions or information about the boot process? Thanks!