Look at the back of UFX III and FF800. You see
- ADAT1 IN, ADAT1 OUT
- ADAT2 IN, ADAT2 OUT
What do you conclude from that?
One TOSLINK cable, one transfer direction for the 8channel at single speed (44.1/48 kHz).
Otherwise, you would see only one plug labeled "ADAT1" or "ADAT1 IN+OUT".
If you want to connect the FF800 to the UFX III and if you would like to use the FF800 for AD and DA as well.
Well, then you need to connect the FF800 with two cables, one for 8ch in sending, one for 8ch in receiving direction.
On both devices, you need to configure the routing of channels from/to ADAT1.
clock master clock slave
UFX III ADAT1 OUT-----------------TOSLINK CABLE 1 ------------------------->ADAT1 IN------FF800
\ /
+ ADAT1 IN<-----------------TOSLINK CABLE 2---------------------------ADAT1 OUT---+
Now you have port ADAT1 completely used.
ADA8200 .. well connect it with two cables to ADAT2 to use the device for AD and DA.
clock master clock slave
UFX III ADAT2 OUT-----------------TOSLINK CABLE 3 ------------------------->ADAT IN------ADA8200
\ /
+ ADAT2 IN<-----------------TOSLINK CABLE 4---------------------------ADAT OUT---+
If you only need AD or DA, well then only 1 cable on the proper direction.
Then you can use the other free port maybe for a 3rd device, if the remaining transfer direction fits.
Please keep in mind, the ADA8200 has DIP switches on the back to configure sample rate and from what port to get the clock.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14