Читаем -> раздел 49.1 http://caxapa.ru/653066.html On-board programming Boot mode (SCI)*1
Channel 1 of the serial communications interface (SCI1) is used for asynchronous serial
communication.
The user area and data area are rewritable.
Boot mode (FINE interface)*1
The FINE is used.
The user area and data area are rewritable.
Boot mode (USB interface)*1
Channel 0 of the USB 2.0 function (USB0) module is used.
The user area and data area are rewritable.
The flash memory can be rewritable in self-powered or bus-powered mode.
A personal computer can be connected using only a USB cable.
Self-programming in single-chip mode
The user area and data area are rewritable using the flash rewrite routine in the user program.