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

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

 

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.

 

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.

 

I was going to say the protocol is the grandfather to CANBUS but why complicate things.

 

That's not actually true, the two protocols have a few similarities but are quite unrelated.

 

I will ask someone about that.

 

Tim is correct. They are quite different, but have a similar purpose.