What does the 2/0 directionality mean
The number of channels alone does not completely specifiy how you can use the chip.
The ADUM1200/ADUM1201 web pages show the difference:


  ADUM1200: Dual-Channel Digital Isolator (2/0 Channel Directionality)
  
  
  
  ADUM1201: Dual-Channel Digital Isolator (1/1 Channel Directionality)