RL78G14 UNUSED XT1/XT2

You can either:
a. Program the pins to P123 and P124 input port mode, and add a pullup resistor to VDD, (or pulldown resistor to VSS).

Or,
b. Set the XT1/XT2 oscillator to enabled and stopped. (then the pins can be left unconnected)
Register CMC, bit5(EXCLK)=0, bit4(OSCSEL)=1
Register CSC bit6(MSTOP)=1

-Mike