CV29 and long address calculator

The two bits of decoder maths everyone ends up doing by hand at some point. Tick what you want and read off the value, or the other way round. Background on what these actually do is on the decoder programming page and the CV reference.

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CV29 calculator

CV29 packs eight independent settings into one number. This covers the six that apply to locomotive decoders — the top two bits are used only by accessory decoders, so they're left out here.

Tick what you want28 or 128 speed steps instead of 14 (bit 1, value 2)Long address (CV17/CV18) instead of the short address in CV1(bit 5, value 32)Custom speed table (CV67–94) instead of CV2/5/6(bit 4, value 16)RailCom enabled (bit 3, value 8)Analogue (DC) conversion allowed(bit 2, value 4)— see the note below before ticking this oneReversed direction (bit 0, value 1)

CV29 = 2

Or type a CV29 value you already have

Ticks the boxes above to show what that value means.

Leave "analogue conversion" off unless you specifically need it

It means the decoder will start driving the motor if it ever sees plain DC on the rails. A dodgy connection or a booster fault can produce something a decoder reads as DC — and a loco setting off on its own is a memorable way to find that out.

Long address calculator

Long addresses (128–10239) are split across two CVs. Ticking "long address" above setsbit 5 of CV29 — without that, the decoder keeps using CV1 regardless of what's in CV17/18.

Address

Enter an address above

CV17 and CV18

Enter both CVs above

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