Bob,
Let me first say that while the decoders under discussion belong to Digitrax there are other decoder manufacturers that are effected in the same way.
This is just a suggestion and works in concept on paper. Earlier this summer I started working on the idea of a DCC comparision web site. Depending on the type of DCC hardware under comparison I have grouped things differently.
In the area of Command stations I have two divisions:
a) entry level
b) full feature
In the area of decoders I have five divisions:
a) N/Z scale decoders
b) HO/O scale decoders
c) Large scale decoders
d) Function Only decoders
e) Stationary decoders
In my comment section of the decoder areas I have a statement that scale is not the only factor in choosing a decoder. I know many HO scale modelers that are using N/Z scale decoders. This usually happens when dealing with small locomotives. As an example several years ago I gave Don Crano a working HO scale Gandy Dancer. It is almost impossible to install a HO scale decoder in it but a Z scale might work just fine.
There is a problem in the standards when dealing with CV7. The Recommended Practices RP-9.2.2 only define CV7 as "This is reserved for the manufacturer to store information regarding the version of the decoder". It does not define how the manufacturer must use it. It RP allows the manufacturer use or not use this space as he sees fit. This allows the each manufacturer to make up their own rules for what is placed in CV7. It even allows for the manufacturer to change their mind. In my opinion at this time CV7 is worthless and should not be used in assisting to identify the decoder.
As I side note I have heard a rummor on several occasions that the NMRA DCC WG has discussed this problem but has not found a solution. I have heard that a solution discussed was the addtion of another recommended CV. In several of these rumors CV7 was to be the model of the decoder and the other CV would be related to the firmware issue and any subsequent changes to the hardware. Of course the manufacturers will have to change the rules they use to insure that the CV7 and this other CV are updated as a change in the decoder is implemented.
Just a few thoughts on my part.
Al
