CMOS is of concern when the signal is connected to a PSoC input. Therefore you may select for a pin as level CMOS or TTL.
Keep in mind, that no signal may exceed VDDA.
Thanks for such a rapid reply as usual.
I know that the DI and DO pins can be set at CMOS or TTL levels. But I can't find any information about the level of the UART pins that will be connected to SIM900B. And the pity is I am not even able to get the level of UART pins of SIM900B from its datasheet that I have shared in my previous post. :(