ADuM3160 configuration

Hi everbody,I'm using adum3160 for isolate the PC and controller board, iCoupler ADuM4160/ADuM3160 USB Isolator Evaluation Board as reference, it's many confused about the PIN, configurated as high level but without response,no much better if LOW.

configuration arguments:

upstream------

VBUS1 : 5V

GND1: PC GND

VDD1: 3.31V

PDEN: 3.31V(connect with VDD1 directly)

SPU: 3.31V(connect with VDD1 directly)

D+,D-, always low.

downstream-------

VBUS2 : 3.3V

GND2: Board GND

VDD2: 3.3V(connect with VBUS2 directly)

SPD: 3.3V(connect with VBUS2 directly)

PIN: 3.3V(connect with VBUS2 directly)

D+,D-, always low.

I'm confused about PC with no response if pull up PIN, and I found that D+(upstream) pulled up to 1.5V if SPD configurate as LOW and SPU configurate as HIGH. it not allowed...