0x00 All you need is a discovery board + a mini-usb cable to computer
0x01 CN3 connected mode: computer – USB cable – onboard STLINK – onboard STM MCU
0x02 CN3 disconnected mode: computer –USB cable – onboard STLINK – onboard CN2 – offboard/other STM MCU
0x03 CN3 disconnected mode is not for offboard USB-STLINK adapter programming discovery board via CN2! This mode turns discovery board to a BIG USB-STLINK adapter for you to develop your own or the third part STM MCU program!