Titan advanced function mapping

Note: page numbers quoted are from the latest QSI manual, version 5.2.0

So, in several documents, the Titan is supposed to support function buttons higher than the NMRA standard mapping of F0 through F12.

But the only documented mapping tool is the NMRA mapping table, CV33 through 46. (page 66)

NMRA Function key mapping

The NMRA mapping allows mapping QSI "features" to a function key for F0 through F12. This table also allows mapping more than one item to a Function Key. Usually you can map up to 8 different items to that Function Key. This allowed a person to map for example the horn and ditch lights to a function key.

These are CVs 33 through 46 (page 66)

A reasonable idea when you basically had only maybe 6 outputs on the decoder.

When sound came around, manufacturers extended the use of the table to include sounds as well as the physical "function outputs" on the decoder.

Since you can (usually) map up to 8 "things" to a Function Key, that suffices for many situations.

Titan extensions to mapping

QSI added an extension on how things work in a Titan (and some other Quantum decoders)

There is a list of "Features" in a Titan, which includes sounds and other things, and these are indeed called "Features" but unfortunately are often abbreviated like:  F12, where people think it is Function Key 12, when it is actually Feature 12.

There is a list of Features (but not complete) on page 121. The Features have a "Feature ID" number.

There are some more Features listed in a different way on page 126, the defaults in most Titans: like Feature ID 62 - System Volume increase.

Note well, that lighting can be specified as in a group, called Multiple Automatic Lights. There are 3 such groups.

You can specify what lighting outputs (up to 12 lighting output ports, shown on the board pinout as LED1 through LED12) are in what lighting groups.


  • You can group lights into one of 3 groups
  • Then map features to what QSI calls Outputs which are NOT the same as the physical LED outputs on the decoder
  • Then map Outputs in the NMRA function mapping "table" using CVs 33 through 46 (page 66)

Note that you can assign up to 8 different "Outputs" to one Function Key, with some restrictions (you see grayed out selections on the NMRA "table"

Note very well that QSI admonishes to NOT map the same "Output" to different keys, it will result in erratic behavior.

"Hidden" QSI Function Key mapping

I noticed (and others have too) that QSI indicates "default" Function Key mappings for (some) Function Keys above F12 (the limit in the NMRA table)

This is in the manual, page 126, but there's more "sprinkled" through other QSI documents, often the user guide packaged with the decoder.

Below is a list that is MOSTLY correct: (I'll try to make it more correct/complete) (I've also tried to correlate the QSI Feature ID where I can:


F11 to toggle between the primary and the secondary horns. (After pressing F11 once, F2 will operate the secondary horn in the normal way.),
F13 to decrease System Volume by 2 dB, feature 63
F14 to increase System Volume by 2 dB, feature 62
F15 to play the Grade Crossing horn sequence (long, long, short, long), but only when the locomotive is moving, feature 154
F26 to start the Fuel Loading Scenario (dialog and sounds appropriate to fueling with diesel oil), but only when the locomotive is stopped,
F27 to start the Maintenance Scenario, but only when the locomotive is stopped,
F28 to start the Water Loading Scenario, but only when the locomotive is stopped.

So by interrogating the QSI Output mapping CV53.PI.SI I found that indeed you could change the SINGLE feature assigned to function keys 13 and up

Note CV53 has 2 settings, one for when it is in FWD or REV, and the other for Neutral (NFF and NFR)

The Outputs run from 1 to 30, so I started by looking at Output 30, and indeed found it was mapped to "Water Load" for F28 (only in neutral)

Continuing to investigate, it seems that Output X gets mapped to Function X-2


F28 = CV53.30.1 = 147 - water load - F28

F27 = CV53.29.1 = 148 - maintenance - F27

F26 = CV53.28.1 = 146 - fuel load -

F25?? cv53.27.1 = 10 short air letoff

F24 ?- cv26

F23? - cv25

F22? - cv24

F21? - cv23

F20? - cv 22

F19? - cv21

F18? -cv20

F17? - cv19

F16? - cv18

F15 - cv53.17.1 =

F14 - cv53.16.1

F13 - cv53.15


- cbell is feature 3

horn 1



from my testing, it appears that FKEY 28 is mapped to output 30



So far I have not tested all of the function keys, but it seems to work.

Note well, you can only map ONE Feature to a Function Key this way (as opposed to using the NMRA Function Key mapping for F0 to F12



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