Talk:Boot ROM

I've replaced reference to MASK ROM by more generic "ROM" since some implementations of boot ROMs aren't masked ROMs at all. E.g. most STM32 chips provide boot ROM but it isn't really masked - it seems to be flashed by STMicro on fab using hardware interfaces into dedicated flash array area known as "system memory", which set readonly after initial programming. From user's standpoint it's a "boot ROM" and can't be distinguished from any other boot ROM. However underlying technology isn't mask-based, more like custom flash controller operations and locking some flash memory read-only. User could also arrange similar sequence on part of user-supplied firmware as well, forcing some flash area read-only, effectively creating user-supplied boot ROM equivalent used to update firmware.

Additionally I've added description of STM32 booting and how it interacts with boot ROM in this particular case based on my experience and STMicro appnotes and datasheets.