Avidyne IFD540 Pilot's Manual page 92

The "Wx Overlay" LSK on the map page brings up a control page
on which the layer combinations can be turned on or off.
Wx Overlay Selection
The options vary with the installed datalink device and
subscription level.
The Wx Overlay page is segmented into groupings of products.
One selection per grouping can be made and products selected
are indicated by a green lamp. The table below represents the
possible set of products available. Products that are not available
due to the device type or subscription level will not be displayed
as selectable choices.
3-16 Map Pages