Seeking Help with Loading Custom Secondary Bootloader via DA14531 ROM Bootloader

Hello Renesas Community,
We’re currently developing a custom secondary bootloader for the DA14531, which we intend to load from SPI flash via the ROM bootloader. However, we're encountering an issue. It appears that while trying to load the secondary bootloader, either:
  1. There’s some form of memory corruption occurring, or
  2. The ROM bootloader refuses to load our custom secondary bootloader.
We are facing challenges to debug due to limited visibility into the ROM bootloader’s behavior. If anyone can help answer the following questions, it would be greatly appreciated:
  1. RAM Usage and Limitations:
    • Which sections of RAM can safely be overwritten by our secondary bootloader, and which should remain untouched during loading?
    • What is the maximum size our secondary bootloader can occupy in RAM? If our bootloader exceeds this maximum size, will the ROM bootloader detect this from the Multipart Header and reject the load attempt immediately? Is there a way to confirm this behavior through debugging?
  2. ROM Bootloader Insight:
    • Is there a way to view or better understand the ROM bootloader code for the DA14531? Any level of detail would help us identify potential conflicts or requirements we may have overlooked.
    • Does more detailed documentation exist for the DA14531’s ROM bootloader, specifically regarding constraints, error handling, and expected behavior during loading? We have reviewed the available documentation, such as the SUOTA Overview, it provides limited details for our case.
Any insights, especially around memory mapping and how the ROM bootloader verifies images, would help us identify the issue we are facing.
If someone has worked on the similar application and didn't face any issue, kindly let us know how they handled the memory mapping.
Thank you in advance for any guidance!