1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Electronics interface problem

Discussion in 'Modding' started by ahmad-al3omar, 27 Feb 2007.

  1. ahmad-al3omar

    ahmad-al3omar What's a Dremel?

    Joined:
    21 Dec 2006
    Posts:
    17
    Likes Received:
    0
    derr all ,, really its urgent please please answer me:
    really i dont understand the next paragraph please if you understand it please expalin it to me:

    The PS/2 protocol includes two signal wires as well as +5V power and ground. The
    signal wires, CLK and DATA, are bidirectional “open-collector” signals; they are
    normally held at a high (+5V) level by a 5–10K pull-up resistor on the host, but either the
    host or the TouchPad device can pull them low at any time. When the port is idle, both
    signal wires are floating high. The host can inhibit the device at any time by holding
    CLK low.
    Note that neither side ever actively pulls CLK or DATA high; to output a logic 1, the
    wire is left undriven and allowed to float high. The CLK and DATA lines should have a
    total capacitance of no more than 500pF to ensure that the 5–10K pull-up resistor is able
    to drive them to a high voltage level in a reasonable time.

    thanks alllllllllot .
     
  2. SteveyG

    SteveyG Electromodder

    Joined:
    23 Nov 2002
    Posts:
    3,049
    Likes Received:
    8
    What is it that you don't understand?

    No active pull-ups are used since it's a bidirectional protocol - both host and node can initiate data transfer. The host or node only actively pull the data lines down to prevent the possibility of a high current path.
     
  3. agent420

    agent420 What's a Dremel?

    Joined:
    18 Apr 2006
    Posts:
    227
    Likes Received:
    0
    I'm guessing that by looking at the functional spec of the PS2 interface you want to use it with some project? If you give more details, perhaps we can point you in a good direction, there are many PS2 projects on the web and you may find much of the work is already done for you.
     
  4. Dreamslacker

    Dreamslacker Minimodder

    Joined:
    13 Sep 2006
    Posts:
    132
    Likes Received:
    8
    Having no electronics training, this is what I can explain:

    There are 2 signal pins on the PS/2 connector. They're connected to collectors that are connected to 5v with a resistor of value between 5k & 12k.
    To represent a 'High' logic ie. Binary 1 bit or switched on etc, nothing is done. When in Idle, both pins are left alone in 'High'.
    For either the host (computer) or device (keyboard/ mouse/ barcode scanner etc) to create a 'Low' logic (Binary 0 bit), it would have to pull the collect low. ie. Short it to GND.

    The host may disable the port by shorting the CLK pin to ground at any time.
     
  5. JazX101

    JazX101 What's a Dremel?

    Joined:
    27 Jun 2004
    Posts:
    99
    Likes Received:
    0
    The gent got the nail on the head with that. It might help somewhat if you were to explain what you're idea is. At the moment all you seem to have is a small part of a soon-to-be-redundant interface standard.
    Jaz_knos
     

Share This Page