M.T.H. HO 4-8-8-4 Big Boy Engineer's Manual page 33

So, in the above example you simply add up the values in the "Decimal Value" row
– 128+64+0+16+8 +0+0+1 = 217. You would write 217 to the CV you were
altering.
The above applies to any CV. Also, if you have a CV that already has a value
assigned that you do not want to alter but need to make additions to it, for example
CV29, you would simply add the additional bits you enabled to the existing value to
obtain the new CV value.
For example, if you had a consist address (CV19) set to 5 and you wanted to alter
this to show an engine reversed in the consist you would need to set bit 7 (decimal
value = 128) for the engine you want to reverse. To do this - take 128 (the new bit
you want to set) + 5 (the existing bit that you do not want to alter) = 133. You
would then write a value of 133 to CV19.
M.T.H. HO 4-8-8-4 Big Boy Steam Engine
33