| 摘要 |
PURPOSE:To demodulate and process plural kinds of signals with a simple constitution by providing an input/output modem with a frequency detecting function, a modulator, a signal processing means, and an interruption instructing means. CONSTITUTION:A CPU has a serial input/output terminal. The parallel input/ output modem 2 in a GII and GII modem and has the frequency detecting function as a GII modem function. At the time of receiving an interruption from a timer 3 programmed in synchronism with the transfer speed during OLD-FM (or FSK) transmission, the CPU 1 reads one-bit data out of a memory 11 and outputs it. The control returns to a main program again after the interruption processing and one bit is outputted at every time an interruption is initiated. The input signal is amplified by an operational amplifier 6 during reception and when the signal is large, the signal is clamped. An FSK demodulator 5 performs frequency detection by zero-cross detection, so the clamped signal is also demodulated normally. The CPU 1 writes the demodulated data in a memory 11 by one bit. At this time, the CPU 1 decides the FSK signal by the frequency detecting circuit of the modem 2 and instructs an interruption to the timer 3.
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