Ports?

Discussion in 'Computing and Networks' started by nanobyte, Aug 1, 2005.

  1. nanobyte

    Thread Starter Senior Member

    May 26, 2004
    118
    1
    Can someone please tell me what exactly is a port? I have a idea, but it is very vague. I know they can set or clear devices and can be used to determine the state of an external device, but I still lack a good understanding of them. I read in a book (C is for control by John Blankenship) that I/O ports are bascially registers made of flip flops. Are all ports like this. I need a detail explanation of what ports are, how they work and how they are used. Any explanation or web resources are welcome.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    The I/O port characterized as a collection of flip-flops is, perhaps, not entirely accurate. A computer could be similarly characterized.

    Naturally, no numbers come to mind, but a web search on serial and parallel ports will turn up more information than you will need. You could include USB as well as the old RS-232 and parallel port standards.
     
  3. n9xv

    Senior Member

    Jan 18, 2005
    329
    1
    A "port" is simply the terminal point where those little 1s and 0s you hear so much about enter and exit the computer or device in question. The 1s and 0s are actually voltage levels. The serial and parallel port voltage levels are known as TTL levels which are 0-volts for logic "0" and 5-volts for logic "1". The serial port inputs/outputs 1s and 0s in a string fashion (one after the other in single file). The parallel port input/outputs 1s and 0s in parallel fashion (all side by side together at once). The USB or universal serial bus port is an easy accsess port for connecting a variety of I/O devices such as printers, cameras, joy sticks etc. You can write data to a port or read data from a port.
     
  4. nanobyte

    Thread Starter Senior Member

    May 26, 2004
    118
    1
    So as address/ data lines allow a microprocessor to communicate with internal devices (i.e. RAM and ROM) ports allow the microprocessor to communicate with external devices (i.e. keyboard and mouse)? Am I correct?
     
  5. n9xv

    Senior Member

    Jan 18, 2005
    329
    1
    Exactly!

    The microprocessor talks to the outside world through the ports. An analogy would be the goods/products of a city getting out to the rest of the world via the shipping "port" used to get those goods to their destination.
     
Loading...