The DCC Standard - A question on transmission

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Hey guys, I'm not sure if any forum members have an in-depth knowledge of the DCC standard and how exactly everything works at the packet and physical layer, but I have a question for anyone who might know. I am using a Beagleboard to create a DCC command station (I am a tinkerer) and I have the general idea of what I am going to do. My question is, what does the command station send out across the track while no data packets are actively being sent? Is it simply a long series of zeros until the next packet preamble, or are DCC idle packets sent during periods of no activity on the rails? Any advice on this is greatly appreciated!
 
I already printed that sheet, but it isn't quite clear from the spec what the controller does at idle. I suppose I will try to determine from an existing controller what goes on. Thanks!
 
If there truly is nothing to send, then the command station will send idle packets, but generally there is something to send. Any time a locomotive is selected on a throttle, the command station will continue to send commands to that locomotive. Even if the loco is stopped, the command station will continue to send packets with the speed set to zero and which functions are on and off.
 




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