The 17e series I believe use a different chip, BM1396. The S15 and S17/e chips (BM1391, BM1396, BM1397) are for the most part pin-compatible. 1396 and 1397 have one functional pin difference, but also a different core count and optimal voltage parameters.

The different modes are passing data left to right, or right to left. There's a Mode pin which gets tied low for one mode, and left floating for the other. This makes serial power and data in a single copper layer pretty simple to achieve.