Disagree - there is no register setting to use Common Anode vs Common Cathode
And that is
precisely the point.
In fact, the chip does not
actually have "segment drivers" or "digit drivers" at all notwithstanding what they are called in the
datasheet - it has
anode drivers and
cathode drivers with each cathode driver corresponding to one register in the chip, and the "Scan limit" register determining how many
cathode drivers are enabled. It does not
care to what you actually connect the lines as long as they connect correctly to anodes and cathodes in a matrix.
so all 8 segments will always be driven - but not all 8 digits (anodes) unless the Scan Limit register is set to 8.
So if we now understand that the cathode drivers are now
connected to segments in a common anode display, then the Scan Limit register will necessarily determine how many
segments are enabled in the multiplex.