SAM3X8E booting confusions

Arduino Due development board contains a 16U2 chip acting as a USB bridge, and also a 1200 baudrate detector. When it detects 1200bps, it will assert a reset and erase pin to clear GPNVM bit.

But my confusion is

  1. Without 16U2, if I upload the sketch through native USB port on SAM, will it detect 1200bps,erase by itself and boots to SAM-BA?

  2. If I want to upload the sketch, the native USB port should be configured to CDC mode. Which code configures this? Is it in SAM-BA?

Thank you for rely!

The native port works only when your program is not completely locked up. If you do manage to write a program which does lock up, then you must manually press reset and hope you can start the upload before it locks up again. Or press erase and destroy your program. This is usually what I end up doing several times per day when I’m debugging.