Dte & Dce

Discussion in 'The Projects Forum' started by McMurry, Jul 12, 2008.

  1. McMurry

    Thread Starter New Member

    Jul 5, 2008
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    These two terms are related to the RS232 serial communication.

    I am connecting my MCU to computer via MAX232 driver IC.
    My computer is the DTE device
    My question is... which one is the DCE device? MCU or MAX232 IC?

    Thanks.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    It's really in how the DB-9 or DB-25 connector is wired. What is an input on a DCE is an output on a DTE, and vice-versa. This allows a DTE to "talk" to a DCE via a straight-through cable. You can have DTE communicate with DTE or DCE to DCE, but you then need to use a "null modem" cable, which has connections crossed (various configurations are used for such "null modem" cables.)

    There's more to it than that, but I don't feel like typing that much :)

    Here's a brief summary tutorial: http://www.advancom.com.au/tutorials/rs232_sig.htm
     
  3. McMurry

    Thread Starter New Member

    Jul 5, 2008
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    urm.. i pretty much understand what's DCE and what's DTE.
    but... my project, the MCU actually sends data to PC via MAX232 driver IC.
    so, is MCU the DCE device or MAX232 the DCE device (because it is the one that actually act as an input to the PC).
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    The uC (mcu) is TTL or CMOS level. The MAX232 translates logic level signals to RS232 level signals. They are not DTE nor DCE devices. They are logic devices, or level translators.
     
  5. McMurry

    Thread Starter New Member

    Jul 5, 2008
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    Aww. in that case, the diagram I drawn is wrong in concept?

    [​IMG]

    Then I think I'll just remove the DCE. Thanks.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    No, it's not wrong. If the RS-232 port at the temperature meter end is wired as DCE, then it's correct.

    It's in the wiring of the port, not the stuff inside the box, that makes it DCE or DTE.
     
  7. theamber

    Active Member

    Jun 13, 2008
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    No is correct if you communicate DCE to DCE or DTE to DTE you will need a tail-circuit buffer placed between the two. And is better if you chose asyncronous mode to communicate.
    Transmit and receive leads (2 or 3) can be reversed depending on the use of the equipment DCE or a DTE.

    Look rs232 data is bipolar 3 to +12 volts indicates an ON or 0-state condition while -3 to -12 volts indicates an OFF 1-state condition.
    Computers ignores the negative level and accepts a zero voltage level as the OFF state. This means the ON state can be achieved with a less positive voltage.So circuits powered by 5 vdc are capable of driving rs232 circuits directly. However the rage will be reduce because of the less potencial but it will work with your device.

     
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