VIM & Toneboard as SPIDF OUTPUT

Hi all,
A user of the toneboard wants to setup his VIM and Toneboard as a simple SPIDF source. He has the VIM and the VIM Toneboard version, and it is suggested in all the threads discussing this feature that this should just work out of the box. However closer examination of the datasheet shows that there is a MODE setting which latches an analogue switch on the toneboard that allows the signal from VIM GPIO 13 to pass to the RCA on the tonebaord.

So two questions:

  • how do you set the mode for SPIDF output on the Toneboard RCA.
  • is the RCA buffered in any way to protect GPIO pin 13 when driving the RCA line ?

Any assistance appreciated.