Hi,
With rs422/rs485 drivers only the differcial voltage is of interest. The voltag referenced to gnd is not very informative.
When a min diff voltage of 2V is given at a 3.3V system, then maybe the one is at 0.5V and the other at 2.5V.
Max possible output voltage is, when both outputs are at their supply rails. So one is at 3.3V , while ghe other is at 0V.
This is max diff voltage if Vcc, = 3.3V.
Vocm that is given with 3.0V makes no sense with 3.3V supply. When one output is at ghe upper rail of 3.3V, then the other must be at 2.7V, but this doesn't fit to the 1.5V min diff voltage. I don't know...
Klaus