Input and output apparatus provided with microcomputer powered from dc-dc converter and configured to operate on clock signal

An input and output apparatus comprising:

• at least a first sub-system and a second sub-system, wherein
• the sub-system includes
• a direct current-to-direct current converter that controls an output voltage to a target voltage by switching a pulse width modulation signal,
• a clock signal generating unit that generates a clock signal, and
• a microcomputer that is supplied electric power from the direct current-to-direct current converter and driven by the clock signal,
• the microcomputer includes
• a pulse width modulation signal generating unit that generates the pulse width modulation signal using the clock signal, and
• a frequency analyzing unit that samples an inputted voltage at a cycle that is shorter than a cycle of the pulse width modulation signal and analyzes the frequency of the inputted voltage,
• the frequency analyzing unit acquires a frequency of the pulse width modulation signal from the frequency of the inputted voltage, calculates a frequency of the clock signal, and outputs a signal notifying an abnormality state of the system, outside the input and output apparatus when the frequency of the clock signal falls outside a range prescribed in advance, and
• the output voltage of the direct current-to-direct current converter of the first sub-system is inputted to the frequency analyzing unit of the second sub-system.