Need help about the TxD and RxD for CurizCore R1001H

hi , does anyone know or can tell me how much voltage is at TxD and RxD pin

the main voltage is 3.2-5VDD . and the digram shows 3.3VDD as the main voltage . so can i assume that the TxD and RxD are +3 and -3 ?

The outputs will be between +3.3V and 0V

thx for helping me with the question