TCA9416: TCA9416

DS of TCA9416  mentions that:

VCCA can be higher than or lower than VCCB. The internal circuitry will select the appropriate supply automatically to correctly support translation.
VCCA can also be the same as VCCB, and the device can be used as a buffer.

In my application VCCA=3.3V and VCCB may be ether 3.3V or 1.8V.

Question:  If VCCA=VCCB is it one direction or bidirectional buffer?

Thanks

Vladimir