AD5522 PMU usb communication problem

I tried to use the measurement chip AD5522 to output a constant 4V voltage。

And I setup all the needed data to the specific regs（as  data x1_reg=CCCC, gain m_reg=FFFF, offset c_reg=8000）

But none right output voltage was get.   I read back all the regs , which are just as the default config(as x1_reg=8000)

So  I doubted that it is a mcu comunication problem. ( QUESTION 1 )

but when i operated in the SWEEPS page as blew,  it  displayed the right output. 

so the communication works just right ???  

And in this config,  the output is clampped  on  1.21V.  ( QUESTION 2)  Actually the defualt Clamp range is from 0000 to FFFF.

Should i suppose to reload mcu firmware or any other moves ?