The computer serial port (RS232) has a total of 9 pins, which are arranged in order, and the definition of each pin is as follows:
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1, pin 1 definition: carrier detection (DCD), Received Line detection (RLSD).
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2, pin 2 definition: Accept data (RXD), is the pin to receive data.
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3, pin 3 definition: send data (TXD), the pin to send data.
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Pin 4 Definition: Data Terminal Ready (DTR), an acronym for Data Terminal Ready.
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5, pin 5 definition: Signal ground (SG)
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6, pin 6 definition: Data ready (DSR), when the modem is started, after its own detection, using DSR to declare that it is ready.
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7, pin 7 definition: request to send (RTS), get sent information.
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Definition of pin 8: Clear send (CTS), clear data. 8, pin 9 definition: ring indicator (RI), issue a prompt.