I am develop an device with firmware upgrade via usb bus. To do it, I would like to do it by:

1: chip bootup address flash address 0 first. it is bootloader firmware now.

2: then, after confirm the application firmware image is OK. Leave bootloader firmware, and jump to application firmware.

I check with current startup_flash.S, don't know how to do it? and not able to more information about the chip booting up.

Need a help on it?