Is there a convention for how a driver should handle frequencies that are not tunable due to tuning step capabilities?

 

For instance, the radio cannot tune 450.611 so the radio refuses user entry (onboard keypad), but when 450.612 is entered the radio automatically adds 500 Hz to make 450.6125.

 

In what functions of the software might the driver raise an exception and where might it auto-adjust a given frequency to fit an available tuning step?

 

Thanks for the guidance,

Brad Schuler

K0BAS