Hack #13. Configure Serial Ports

Starting with a clean, industry-standard serial port configuration can save hours of headaches when you're ready to add more devices.

If you currently or eventually will have to connect your PDA, a modem, a GPS unit, an uninterruptible power supply to protect your PC, or something else to a COM port, leave the COM port(s) enabled with a known configuration. If you know for sure how your ports are configured, it makes using them much easier.

There are several ways to tell if you have one or more COM ports on your system:

  • Look at the back (sometimes the front for some COMPAQ and HP systems) of your PC to see if there is a connector with nine small male pins in two rows—one of five pins, the other of four pins, surrounded by a trapezoidal or D-shaped metal shell—or a connector with 25 male pins in two rows of 13 and 12, respectively. These are known as DB-9 male and DB-25 male connectors, respectively. Only serial ports have this style of male connectors.

    The presence of these connectors does not tell you specifically that there are COM port electronics wired between the connectors and your system board—these may be fillers for the addition of COM ports to a system that does not have them.

    The presence of these connectors also does not tell you if they are connected to an add-in card plugged into an ISA or PCI slot or directly to COM port electronics on the system board. Only a physical inspection of the inside of your PC can tell you for sure ...

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