S/PDIF is not limited to 48kHz. But, because of its reduced electrical specifications, we don't recommend its use at higher rates.
ADAT, on the other hand, IS limited to 48kHz. There is a higher frequency variant known as S-MUX, that will operate at higher rates, but with half the number of channels. This format is not supported by Eclipse.
If you are working with a DAW, Wordclock is probably the way to go. Depends on your hardware…
