Questions about ADF MODULE_VARs

#1
Ok... now I want to be sure I understand:

ADF_FREQUENCY, // |
ADF_500_HZ_TUNABLE, // | ADF frequency
ADF_EXTENDED_FREQUENCY, // |

As we know from the FAA and other resources, the ADF receiver can tune:

190.0 kHz - 1799.0 kHz

This allows pilots to tune:

NDBs: 190.0 kHz - 535.0 kHz (in CONUS)
AM: 535.0 kHz - 1799.0 kHz (Used by AM radio stations)

Finally, outside of CONUS some countries use 500 Hz increments (ie. 0.5 kHz steps).

So, I know that:

ADF_FREQUENCY

is returned as a BCD value in an UINT32 with that being in whole kHz (ie no 0.5 for outside CONUS).


Code:
  32                                           0
   X X X X  X X X X  X X X X  X X X X
     1000s     100s      10s       1s
Hence, at some point I'm guessing MS added:

ADF_500_HZ_TUNABLE

which is a boolean that when true means:

ADF_EXTENDED_FREQUENCY

is defined. This is also a BCD value but I am unsure of the coding, but suspect it encodes the 0.5 kHz digit.

Can someone clarify this one? :D

Patrick
 
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