AD9783: the function of REFIO

Hello ,

I have a question about the function of REFIO of AD7983.

In the pin descrition tabe, Table 8, REFIO pin is described as "Analog Reference Input/Output (1.2 V Nominal)."

This description include "Input", but I think that the AD7983 is not able to use with external reference.

The block diagram of reference circuit is indicated in page of 28 of datasheet,  I think the AD7983 can be operated with internal reference.

Is this understanding correct?

 

Best regards,

ysuzuki