Posted on January 28, 2015 at 10:51Clive,
I'm really sorry, but now you're pissing me off.
There is no reason for the bootloader to mess with the internal clock settings. The bootloader tries to ''clean up'' after itself and resets the register ''to its reset value'' as documented under ''limitations'' for the '051. However someone at ST didn't read the manual properly and the reset-to-zero is NOT the reset value.
Why do you document ''reset values'' for registers? That's so that you can optimize. Some registers do not need initializing because their reset value is already as you want it.
But even then, a processor like the STM32-series is so complicated with over 1000 pages of ''reference manual'' that it is impossible for normal humans to read through and remember everything. So the processor is and needs to be designed so that many modules that a user won't need are initialized in a way that it is not necessary to read the manual for that module.
So now there is a register documented as: ''reset value is 16'' and that's exactly what I want. For future compatibility, do I explicitly write it to 16 because that's what I want, or do I leave it ''at reset value'' to keep as much future-compatibility as possible?
The bootloader is documented to be able to boot from several devices and it is documented to leave those devices in a possibly enabled state when leaving the bootloader. However, This is not mentioned.
The proper response is: ''You might be right, we'll investigate, and if it turns out you're right, we'll document it as a ''limitation'' and fix it for future revisions. Thank you for reporting this''.
Saying: ''it is all your fault!'' is not making any friends.
