| 摘要 |
PURPOSE:To obtain an inexpensive D/A converter, by finding the duty ratio of a pulse string of a fixed period by means of a CPU in accordance with the set value of the output level of an analog signal, into which a digital signal is to be converted, and smoothing the pulse string whose duty ratio produced by a program timer is changed. CONSTITUTION:A microprocessor (cpu) 23 which converts a digital signal into a clock pulse counting set value in accordance with the set value of the output level of the analog signal, into which the digital signal is converted, and outputs a start command and the clock pulse counting set value by means of an interrupt signal 30, and a program timer 24 which is actuated by writing the clock pulse counting set value outputted by the cpu 23 upon receiving the start command outputted from the cpu 23 and counts clock pulses until they reach the clock pulse counting set value, and then, outputs the clock pulses as a pulse string whose duty ratio changes at a fixed period, are provided. The pulse string outputted from the program timer 24 is smoothed by a low pass filter circuit 28 and analog signals are outputted.
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