CV29 Explained

Ed's quick and easy tip to wrap your head around CV29: Think of it as a bank of 8 toggle switches and NOT as a real number that can be adjusted like a volume control knob. Inside CV29, each bit has a unique meaning. Here is a listing of the bit meanings: 

Bit 0 ON [1] = Direction of operation is reversed
         OFF [0] = Direction of operation is normal

Bit 1 ON [1] = 28 Speed Step Mode (should always be enabled)

Bit 2 ON [1] = Analog mode operation enabled
      OFF [0] = Analog mode disabled

Bit 3 is  Railcom and is usually ignored by the DCC system firmware.

Bit 4 ON [1] = Alternate Speed Curve Active OFF [0] = Use table defined by CV 2, 5 and 6

Bit 5 ON [1] = Use long address in CV17/18 OFF [0] = Use short address defined in CV1

Bits  6 and 7 are ignored by the DCC system firmware.

Now to transfer the state of all of the individual bits as a single numeric value is where the confusing part comes into play. What is required is a little binary mathematics to calculate the final numeric value but even that is pretty easy once you know how to do it. First, start by reading a bit string from right to left. As you move to each successive bit to the left, you will notice that the bit value doubles from the previous bit value.




I found this really useful CV29 tool online   

A handy CV 29 calculator



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