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I am trying to understand about secondary bootloader. Let us say we are talking about a specific 32-bit ARM MCU then is it possible to find out whether the secondary bootloader can load a firmware in RAM or is it that it always load and bake the firmware in flash-rom? Or does it vary from case to case basis? So far what I understand is that a secondary bootloader only contains flash-rom driver and not ram-driver for the specific MCU chip. So it can only flash a firmware in flash rom. While a primary bootloader, the on-chip boot ROM, has RAM driver and it can load the secondary bootloader into the RAM memory. Please correct me if I am wrong.

Marina
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  • *"Let us say we are talking about a specific 32-bit ARM MCU"* Your terminology needs to be more concise and specific. The SoC you refer to is described by the manufacturer as a MPU rather than MCU, because it has a MMU and no integrated/embedded NAND flash. *"Secondary bootloader"* is ambiguous, as some people don't count the ROM boot code and/or choose to ignore it. You seem to overlook the case of NOR flash, which allows XIP, execute in place. You use the `u-boot` tag, but U-Boot can be a boot program that is "loaded" by its SPL, Secondary Program Loader. – sawdust Feb 06 '22 at 01:28
  • *"Flash ROM"* is a nonsense combination of words. Although tablet and smart phone marketing blurbs may refer to NVM (such as NAND) as *"ROM"* as a convenient way to differentiate flash memory capacity from volatile "RAM" capacity, this site should use established technical definitions rather than sloppy marketing jargon. IOW by definition, you cannot write or reprogram ROM. – sawdust Feb 06 '22 at 01:49

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