Avr2054 Serial Bootloader User Guide

Hello:I'm looking for a Bootloader for SAMD10 and reading 'Atmel AVR2054: Serial Bootloader User Guide' which provides examples for different AVR and SAMR21 parts, there are some things not very clear to me. According the Application Note, the bootloader firmware is flashed in the device, and after reset it executes and connect to a PC program to download the user application.

1. Avr2054 Serial Bootloader User Guide Download

Avr2054 Serial Bootloader User Guide Download

The downloaded user application is then flashed in the device (in a higher address space in flash) and executed once this process is finished.However, if the user application is not starting at flash address 0x00, then it should be linked to start in a different address. But there is no mention about this.I'm wondering how this really works.I would appreciate any comment on this.ThanksGus.

One option seems to be Xboot + avrdude. Avrdude was too obvious and I didn't realise it works with bootloaders as well. Is Xboot a good choise?I need to use DFLL. The manual says '3.1.1 USEDFLL This will turn on the DFLL for the selected oscillator, improving its accuracy. Recommended for high serial baud rates.'

I can't understand the logic behind recommending only for high baud rates. Isn't clock accurcy just as important for lower baud rates?The USEDFLL seems to be on by default (in xboot.h, not in conf files), but it only sets the DFLLENABLEbm, which does nothing without setting the OSCRC32KENbm.Why is there 4 bytes in xboot.eep after compiling?

I couldn't find any EEMEM variables in the code.