What is the resolution of the ADC Channels?
On https://www.arduino.cc/en/Main/ArduinoBoardZero the summary describes the Analog Input resolution as "6, 12-bit ADC channels"; however, later it also says "Analog Inputs. Six of the 20 general purpose I/O pins on the Zero provide analog input. These are labeled A0 through A5, and each provide 10 bits of resolution (i.e. 1024 different values)."
When I use an AnalogRead on my my Zero to read the 3.3V pin, I'm getting a maximum value of 1023, which indicates the Analog Input resolution is 10-bit. What am I missing? Is the ADC 12-bit but only 10-bits are being used for compatibility reasons? Can the extra 2-bits of resolution be enabled?