Avidyne IFD540 Pilot's Manual page 24

A second way to manually tune a frequency is to touch the Active
or Standby frequency slot and when a virtual keyboard is
displayed, type the desired frequency into the numeric keypad
and press the Enter ("Enter" on the virtual keypad or "ENTR" on
the bezel) button. The numeric keypad will time out and be
removed after 10 seconds of inactivity.
Another way to manually tune a frequency (only useful for tuning
VOR Nav frequencies) is to type the identifier of the desired
frequency (e.g. "GDM" for the Gardner VOR) via the
alphanumeric virtual keypad. An automatic, geographic-based
prediction algorithm ("geofill") is running such that the most likely
VOR station is filled in based on your geographic position.
Manual Entry of VOR Identifier
A more automated way to tune a com frequency is to press the
"FREQ" button along the right edge of the bezel. This will present
a list of likely frequencies and that list can be scrolled via an
up/down motion with touch or via twisting the right hand knob. If
touch was used, double tap on the row that you want to put into
the #1 Standby. If the knob was used to scroll through the list,
push the knob in to put the frequency into the #1 Standby slot.
Frequencies can also be nominated to be put into the #1 Standby
from other pages on the IFD540 such as the INFO or NRST Tab
on the FMS page.
1-18 System Overview