Decoder Reset CV Value

[maxman]

This is basically a curiosity question.  If I have a decoder that wants to have a value of 8 entered into CV 8 to reset, and I enter this value to reset the decoder, what happens if I then enter some other number into CV 8?

Will the decoder only respond to the value of 8 and ignore the new number, or will strange things happen?

Thanks

Thanks

[Stevert]

By definition, CV8 is a read-only CV.  So when you "write" to it, all you're doing is sending a command that the decoder interprets in a specific way. 

For example, Digitrax decoders have a CV8 (Mfr. ID) value of 129.  But if you "write" a value of 8 to CV8, it will do a complete reset.  And if you "write" a value of 9 to CV8, it will reset everything except the speed tables.  But it does that by interpreting those commands.  In no case does the value of 129 ever get changed.

To directly answer your question, as far as I know, if that command isn't structured properly (contains the wrong value), the decoder will just ignore it, although I'm sure there may be some decoders with poorly-written firmware that will behave otherwise.

Steve 

 

[tbdanny]

There may be other commands as well - I know that the BLI Paragon2 decoders will remap the keys to match other brands of sound decoders for certain 'values' programmed into CV8.

Thanks for that reply, Steve - I was wondering how that could have worked.

[mfm37]

 If you try to write a value to a CV that it either doesn't recognize or is out of range, the decoder ignores it.