I'm currently developing a programm which I will debug on the ATtiny3217 XPlained Pro Board, but which will later run on an ATtiny1616 (according to the description of the board, it's the right one to develop for the ATtiny1616). I'm therefore working with both documentations at the same time, trying to notice difference.
A major difference I just found is in the VREF register - according to my understanding the documentation of the ATtiny3217 is just not complete here.
Technically ADC0, AC0, DAC0 as well as ADC1, AC1, DAC1 and DAC2, AC2 can use the internal reference. In the documentation of the ATtiny1616 the registers to set up the reference voltage are well documented and understandable. Here's a quick overview:
VREF.CTRLA: Set reference voltages for ADC0, DAC0, AC0
VREF.CTRLB: force reference voltages for any of the modules mentioned above
VREF.CTRLC: Set reference voltages for ADC1, DAC1 and AC1
VREF_CTRLD: Set reference voltages for DAC2 and AC2
Since the ATtiny3217 provides exactly the same functionality, the registers should look just the same. However, in the documentation only CTRLA and CTRLB are mentioned. It is to be noticed that CTRLB is just the same as in the ATtiny1616 documentation, therefore provides bits to force reference voltages for ADC1, DAC1-2 and AC1-2. Yet, since CTRLC and CTRLD aren't mentioned in the ATtiny3217s documentation, there's no option to set these reference voltages.
Now here's my question: Is the documentation of the ATtiny3217 just incomplete and doesn't cover the registers VREF.CTRLC and VREF.CTRLD or did I missunderstand something here?
EDIT: Little side note - when developing in Atmel Studio for the ATtiny3217, one can set VREF.CTRLC and VREF.CTRLD without getting a compiler error. At this point I'm pretty sure we're dealing with a faulty documentation here.