Patent ID: 8508177

Claim:
A stepping motor drive device, comprising: a first pulse generation circuit configured to generate pulses in synchronization with either rising edges or falling edges of a first clock signal; a second pulse generation circuit configured to generate pulses in synchronization with both rising edges and falling edges of a second clock signal; a first clock determination circuit configured to determine whether the first clock signal is normal; a second clock determination circuit configured to determine whether the second clock signal is normal; a first mask circuit configured to receive an output of the first pulse generation circuit, and output the output of the first pulse generation circuit as it is if the second clock signal is not normal or mask the output of the first pulse generation circuit if the second clock signal is normal; a second mask circuit configured to receive an output of the second pulse generation circuit, and output the output of the second pulse generation circuit as it is if the first clock signal is not normal or mask the output of the second pulse generation circuit if the first clock signal is normal; a logic circuit configured to logically combine outputs of the first and second mask circuits; a step position control circuit configured to determine a step position of a stepping motor according to an output of the logic circuit, and a motor drive section configured to supply a current to the stepping motor according to an output of the step position control circuit.