CrossRoads:
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.
CrossRoads:
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.