I've been going through this datasheet and I don't understand what is meant by 'OTP' for selection the function of the GPIO pins. The function select table can be found on page 20. I'm also confused why it refers to inputs and ouputs as CMOS and NMOS. Can someone explain this?
They're not referring to CMOS or NMOS, the options are CMOS or N-Channel open-drain.
The CMOS option can push or pull the pin up or down, while the open-drain option can only pull the pin down (relying on an external pull-up resistor).
OTP is almost certainly referring to One-Time-Programming.
There doesn't seem to be any indication in that document on how this programming is done though.