Numerical control system including internal register self-reset function with serial communication signal monitoring

A numerical control system comprising:

• a numerical controller;
• and
• one or more I/O units connected to the numerical controller, the numerical control system performing transmission and reception of input and output signals using serial communication between the numerical controller and a first I/O unit, wherein
• the first I/O unit includes a monitoring part that monitors a serial communication signal transmitted from the numerical controller,
• the monitoring part includes circuitry including
• a transmission and reception part that receives the serial signal from the numerical controller or a second I/O unit at a front stage relative to the first I/O unit and transmits the serial signal to a third I/O unit at a subsequent stage relative to the first I/O unit,
• a determining part that determines that a power supply of the numerical controller is stopped when the serial signal is stopped for a predetermined time or longer,
• a stop part that stops the serial signal to be transmitted to the first I/O unit at a subsequent stage when the determining part determines that the power supply of the numerical controller is stopped, and
• a reset signal output part that outputs a reset signal to a register inside the first I/O unit when the determining part determines that the power supply of the numerical controller is stopped, wherein the register inside the first I/O unit is reset based on the reset signal.