Running a DC loco with NCE and DCC address “0”

Using Address “0” by Mark Gurries

Message on the DCC4EVERYONE Yahoo list, Sep 26, 2006.

Bram Bailey said

“The bottom line is that the 00 address was put in the NMRA's original specification for political reasons to satisfy those who would cling to DC until they die. In practice, very few people actually use that feature and I believe that is was removed from a later version of the NMRA specification”.

Mark replied.

This is a false assumption and is all made-up gossip.

Short Address 00 on the track is actually a reserved NMRA locomotive address per DCC Standard S9.2

Per DCC RP-9.2.1, this address is used as a global decoder address to talk to ALL DCC LOCOMOTIVES at the same time. It called the Broadcast Address. Commands like Emergency Stop can be sent down the track at address 00 and every locomotive on the layout will stop with this one command! It has always been this way and there have been no changes to the NMRA standards and RP's in this regard.

The problem thus becomes when one enters short address "0" on the cab or throttle, he or she will have GOD like control over every engine on the layout at one time. Blow the horn, they all blow at once. Turn up the speed, they all move!

Not good or useful from an Engineer/Operators point of view. Thus DCC locomotive address 00 from the Cab/throttle level is not allowed to be accessible!!

Thus becomes the problem, what does one do when the user enters short address 00 into the cab/throttle?

Another thing you need to know is that the DCC Standards and RP did NOT provide ANY support from a locomotive address point of view on how access and control a DC locomotive placed on DCC powered track. The standards only provided the DCC protocol on how to modify the DCC signal such that it can FOOL a DC locomotive into moving on the track! (It does not put DC out on the track. The power remains a special form of AC, which is why the locomotive buzzes even while standing still! DCC signal are being sent down the track all the time but the DC locomotive does not know what to make of it and does nothing.)

Thus becomes a second problem, how to access a DC locomotive from a DCC throttle?

Both of these problems were left up to each DCC manufacture to figure out if and how they would support a DC locomotive on DCC powered track.

Some manufacture simply decided NOT to support DC locomotives. NCE is one manufacture that has gone down this path. Others like Digitrax and Lenz took the two independent problems, put them together, and came up with solution to access and control a DC locomotive. Thus short address 00 become a very special command that ONLY the command station recognizes as a throttle command to modify the DCC signal/waveform to conform to the protocol needed to run a analogue locomotive. It does not change any DCC commands packet information but only slows down how fast they can be sent.

Summary (not in any order)

1) Address 00 at the cab to control a DC locomotive is not part of any DCC standard. It just turned out to be a easy solution to a problem.

2) DC locomotive support depends on the DCC Manufacture. If there is anything controversial to be had, it is this! Lots of people think this is a great security blanket in adopting DCC but reality has shown its not. Once you switch to DCC at see and hear the advantages, there is never any going back to DC. Time tested proven statement!

3) Many locomotives manufactures have stated they do not support running a DC power locomotive on DCC power track. Why, the motor can get hot doing nothing! Check your warrantee.

4) Running an analogue locomotive compromises the response time performance of all the DCC controlled locomotives. Thus large layouts often ban its use.

5) There never was anything politically involved in this locomotive control process. Please do not repeat this false information.

6) I suspect when the DCC standard were being written way back in the early 90's that there might have been some strong debates as to supporting DC on DCC. (I was not part of DCC at the time myself).

Since DCC was still NOT a proven product at that time, "Marketing Sense" would have said that one must provide a way in the DCC standards to make it possible to have a back door and/or security blanket for people sitting on the fence about adopting DCC. But is was written and done in such a way as to not be a DCC REQUIREMENT so manufactures who did not want to support it did not have to! With that agreed upon...things moved forward...debate over.

Mark also wrote on the Yahoo DCC4Everyone group on 03 March 06

FYI:

Loco address 0 has nothing to do with it. The NMRA DCC standards & RP's DO NOT say a analog loco must be at address zero (long or short loco address). Informally some DCC manufactures have chosen to use short address zero, as entered on the Throttle/Cab, for analog loco control.

What the DCC standards DO say is that loco Short Address 0 as sent on down the track is reserved as a special BROADCAST command to ALL locos regardless of their programmed/active address is and they must ALL process this command. Assuming you could actually send a DCC command to loco address 0 (short) such as turn on headlight (F0), every single locomotive on the layout will turn on its headlight! Thus given its special power, usage of this address is and must be very restricted. An example of a perfectly VALID DCC command sent to address 0 would be emergency stop.

What really happens is the command station decides when to use loco address 0 depending on what command you give the command station.

Although your are not permitted to directly control address 0 on your own, long Address 0000 is NOT a special address and has none of the power that short address 0 has. Thus per the DCC standards, long address 0000 is a valid loco address. (Not all DCC systems support long addresses below 128)

Given this restriction on short Address 0 at the track level, DCC manufactures have two choices as to what to do with short address 0 when it is entered at the throttle/cab (user) level:

1) Use it for something else such as DC/ANALOG Loco control. Digitrax, Lenz and some others have chosen this path*. When you select Loco 0 on the throttle, the command station then reroutes the speed and direction command sent by the cab into creating special signals (NOT related to DCC commands) to the track which a standard DC (analog) loco will interpret as DC power and run.

2) Do not permit access at all.

NCE has chosen this path for it actively made a company policy choice to not support ANY DC/Analog loco control operation with its DCC systems (Does not effect NCE decoders which do support DC operation). When you attempt to select Loco 0 on the throttle, the address is refused. Other DCC systems may have made the same choice*.

*Except as noted, I cannot remember who ELSE has done the same at the moment.

Hope this helps.

Best Regards,

Mark Gurries

Linear Technology

Power Supply & Battery Charger Applications Engineer/Manager

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Model Railroad Club and NMRA DCC presentations are at:

http://www.siliconvalleylines.com/index.html

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Audio Enthusiast (Love SAE equipment)

http://members.ebay.com/aboutme/gurriesm/

Running a DC loco with NCE and DCC address “0”.

Dennis Blaker asked about NCE’s Power Cab on Yahoo DCC4Everyone group on 03 March 06

Unit appears to be feature packed.

After reading the manual I still can't determine if this unit supports non DCC equipped engines. Any information on this unit (NCE Power Cab) would be greatly appreciated.

There is no function for a number zero or non DCC loco. Any DC loco placed on the track will have lights on and the motor will whine, but you will not be able to control the loco.

Mark Gurries replied

Correct. In fact there is no DC/Analog loco support with ANY NCE DCC system for that matter.

FYI:

What the DCC standards DO say is that loco Short Address 0 as sent on down the track is reserved as a special BROADCAST command to ALL locos regardless of their programmed/active address is and they must ALL process this command. Assuming you could actually send a DCC command to loco address 0 (short) such as turn on headlight (F0), every single locomotive on the layout will turn on its headlight! Thus given it's special power, usage of this address is and must be very restricted. An example of a perfectly VALID DCC command sent to address 0 would be emergency stop.

What really happens is the command station decides when to use loco address 0 depending on what command you give the command station.

Given this restriction on short Address 0 at the track level, DCC manufactures have two choices as to what to do with short address 0 when it is entered at the throttle/cab (user) level:

2) Do not permit access at all.

*Except as noted, I cannot remember who ELSE has done the same at the moment.

Hope this helps.

Best Regards,

Mark Gurries

Linear Technology

Power Supply & Battery Charger Applications Engineer/Manager

---------------------------------------------------------

Model Railroad Club and NMRA DCC presentations are at:

http://www.siliconvalleylines.com/index.html

--------------------------------------------------------

Audio Enthusiast (Love SAE equipment)

http://members.ebay.com/aboutme/gurriesm/

----------------------------------------------------------

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