I did not have description of the value of Vih (min), Vil (max), Voh (min), and Vol (max) found by data sheet of cc2533.
Vdd of CC2533 is described to be 3.6V from 2.0v.
My customer thinks that I would like to carry out cc2533 and interface by 1.8V LVTTL.
Regards, Hidetaka.