Patent ID: 8305191

Claim:
A semiconductor device comprising: an antenna circuit configured to transmit and receive a signal; a signal oscillating portion comprising: a first rectifier circuit configured to rectify the signal received by the antenna circuit; a first power supply circuit configured to generate a first direct-current voltage by smoothing an output of the first rectifier circuit; and a ring oscillating circuit configured to generate an oscillating signal using the first direct-current voltage as a power source; and a signal processing portion comprising: a first counter configured to count the number of oscillations of the oscillating signal; a second rectifier circuit configured to rectify the signal received by the antenna circuit; a second power supply circuit comprising a regulator and configured to generate a second direct-current voltage by smoothing an output of the second rectifier circuit; a reference clock generation circuit configured to generate a reference clock using the second direct-current voltage as a power source; and a logic circuit comprising: a CPU; and a second counter configured to count the reference clock and output a counter value of the second counter to the CPU at a time when a counter value of the first counter reaches a predetermined value.