How does communication take place through a cat 5 cable in CBUS

Discussion in 'General Discussion' started by jayantc11, Jun 6, 2012.

  1. jayantc11

    jayantc11

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    Could someone please provide an answer to the following doubts of mine ( or provide a link which could answer my doubts):

    How does communication through a cat 5 cable exactly take place in cbus? Which wires actually carry the message signals? and how does the protocol exactly work ? how many start bits stop bits etc. which kind of modulation is used to encode the messages? I know ive asked quite a few questions here but i would be really grateful if someone could be willing to help me out.

    Thanks
     
    jayantc11, Jun 6, 2012
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  2. jayantc11

    tobex

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    The protocol is very similar but not identical to RS485 differential serial, multi-drop.

    There are two wires for the negative voltage and two wires for the positive voltage. The system is balanced for the 300ohm Category 5 wire impedance.

    The system voltage is a nominal 36V but can be lower with loads.

    The stop and start bits are defined by the serial protocol standards written by clipsal.
     
    tobex, Jun 6, 2012
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  3. jayantc11

    Ashley W

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    You know if you look at the install sheet for any C-bus device it will show you exactly the wires that are used. Specifically they are the orange and blue pair, however unlike Ethernet which uses a colour and white pair for each direction, C-bus is not directional (being a bus) and splits the pairs by using the orange and blue both to carry the +'ve signal with the corresponding white mates carrying the return.
     
    Ashley W, Jun 6, 2012
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  4. jayantc11

    ashleigh Moderator

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    Not quite, but close. It is actually a lot more complex than that, and it allows genuine multi-cast addresses with multiple devices transmitting at the same time, with collision detection, resolution, backoff, retry, and multi-mastering. (Something, incidentally, that nothing else does properly.)
     
    ashleigh, Jun 7, 2012
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  5. jayantc11

    tobex

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    I was going to say the protocol is the grandfather to CANBUS but why complicate things.
     
    tobex, Jun 7, 2012
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  6. jayantc11

    TimB C-Bus Systems Engineer

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    That's not actually true, the two protocols have a few similarities but are quite unrelated.
     
    TimB, Jun 8, 2012
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  7. jayantc11

    tobex

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    I will ask someone about that.
     
    tobex, Jun 8, 2012
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  8. jayantc11

    Darren Senior Member

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    Tim is correct. They are quite different, but have a similar purpose.
     
    Darren, Jun 8, 2012
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