Posted on June 29, 2017 at 17:54I believe that the system loader should manage the FLASH registers. You get to erase blocks, and read/write data into the array.
It's not my battle, so I haven't spent hours digging into it, but the point at which built in ROM boot loaders cease to be helpful you typically push your own loader code into RAM which can have a better protocol and a richer implementation, that fully supports the specific facets of the board as implemented. This kind of staged or tiered loader model is very prevalent in SoC designs.
For these devices I'd recommend having your own boot loader which resides in the first 16KB block (can be bigger if need be), and have your application code separate, where the boot loader can validate the image before jumping into it. For the Dual bank model where you basically replicate the first MB into the second MB, the loader can still manage the image used, set the BPB bit, and fork to the appropriate one (figure a sequence number can determine the newest one).
I would recommend you start by getting comfortable with the system boot loader, you can do this in an interactive manner, and once you are comfortable with how it works, and how that fits with what you want to achieve, then decide how you want to partition the programming application vs the image you want to deliver to the part. Programming applications used for production programming tend to differ from those for field/user programming.
