The T100MD888+ has two serial ports. The COMM1 RS232 port is full duplex whereas the COMM3 RS485 port is half-duplex.
However, all the PLC communication protocols supported are essentially half duplex since they all depend on the master sending the completed command to it and it will then process the command and send back the response string. However, if the master were to send the second command string to the PLC's RS232 port before the PLC completed sending the response string to the first command, then the incoming characters will be queued in the PLC's serial receive buffer up to 256 characters.