Yamaha AW2816 Owner's Manual page 267

F
DIGITAL ST IN SYNC CAUTION
When this button is on, an error message will be
displayed in the lower part of the screen if a signal
not synchronized with the word clock source is
being input to the DIGITAL STEREO IN connector.
(Default setting = on)
G
OPTION IN SYNC CAUTION
When this button is on, an error message will be
displayed in the lower part of the screen if a signal
not synchronized with the word clock source is
being input to a digital I/O card installed in the
OPTION I/O slot. (Default setting = on)
Reference section
265