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# CV29 Explained

How to change a CV

https://ncedcc.zendesk.com/hc/en-us/articles/205071359-How-to-view-or-change-a-CV

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.

How to change a CV

https://ncedcc.zendesk.com/hc/en-us/articles/205071359-How-to-view-or-change-a-CV

I found this really useful CV29 tool online

A handy CV 29 calculator