Dataref for airspeed kts vs mach

[Sergey22]

Hi All,

I'm working on integrating Challenger with the winwing PAP3 panel. The PAP3 panel can indicate with speed selector is Kts or Mach, just like on PFD speed tape, but I'm struggling to find a dataref which indicates the mode that's selected. 

Any suggestions?

[Sergey22]

For what it's worth I did manage to find it - abus/CL650/ARINC429/FDCU-1/words/FCC/0/IAS_REF . It's set to 1 when Mach is used and 0 if IAS/kts.