Mike,
CV29 controls a number of functions - e.g. reverse direction, 28/128 speed steps, dual-mode/DCC-only, loadable speed tables, and make decoder address 128 or higher. Each of these functions is activated using a particular value and the sum of their values is what is entered into CV29.
Here are the (default) and activation values for a TCS decoder:
Say you want your F3 to have an address higher than 128 and use 28/128 speed steps, you would enter a value of "34" for CV29, or 32+2=34. In order to activate dual-mode (DC) operation along with the other two functions, you would need to increase the value of CV29 by four to "38", or 32+2+4=38.
Now, say you wanted to reverse the direction of your F3 because it ran in reverse in the forward position, you would increase CV29 by one to "39", or 32+2+4+1=39. And if you decided to turn off dual-mode operation so that your F3 only operates on a DCC layout, you would decrease CV29 by 4 to "35", or 32+2+0+1=35. Does that make sense, Mike?
Most decoder (default) sum totals for CV29 are "6", which would activate 28/128 speed steps (2) and dual-mode (4), or 2+4=6. Use your Power Cab in Programming track mode so that you can read back the value for CV29 then activate the functions you desire.
Hope that helps...
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
I have an Athearn Genesis F3A and a F7B, they are in a consist together, When I power up my NCE power cab they run backwards about 10" and stop, even if they weren't the last engines used prior to shutting down the system. I spoke with NCE and they told me I needed to disable the DC for those engines. He said its CV 29, but he wouldn't tell me howto do it because there are"too many different decoders". So is he correct, and if so how do I do it?