Optical or Coax, SPDIF will support transmission of clock in both directions. As such, if an external device has both SPDIF In and Out ports and both are connected to your interface, that external device can work as either a Clock Master or Slave. If connecting ONLY the external device's SPIDIF In or Out to your interface, then the choices are limited as per the text quoted from the Ultralite Mk5 manual: an external device that is connected only by its SPDIF In port must necessarily be a Clock Slave. If connected only by its SPDIF Out port, the device must be a Clock Master.
As you know, only one device, your interface or an external device, can be the Clock Master. This is not an issue as long as there is no more than one device connected by only its Digital Output.
I have a fairly typical system with three devices connected digitally: My MOTU Interface, a PreSonus external expander that provides eight channels of analog I/O via optical I/O, and a Lexicon reverb with Coax SPDIF I/O. The external devices are digitally connected both to and from the interface. As such, any single device could serve as the Clock Master. The Master device must run from it's internal Clock. The other two devices must be set to Receive External Clock to Slave to the Master Clock.
In my case, my interface runs from its Internal Clock. There is a setting in the interface that allows this. (The Ultralite has a similar setting option, and the clock source is displayed on its front panel.) My PreSonus receives the interface's clock via a Word Clock BNC connection, but it could receive that same Clock from its Optical In Port. The Lexicon receives clock from its SPDIF In Port. Both the PreSonus and Lexicon are set to receive external clock.
fredrick wrote: ↑Tue Feb 01, 2022 1:51 amOK, but what about when
both S/PDIF inputs and S/PDIF outputs are being used simultaneously? If I use Clock Source = S/PDIF, will the S/PDIF output inherit the input sources clock? If so, will I lose the S/PDIF output if the S/PDIF input source is shut down??
You can certainly connect two external devices simultaneously using both the Optical and Coax ports and designate either Optical In or Coax In as Clock Master. Clock signal fed to the Ultralite via either of its Digital In ports (Optical or Coax) will be passed through to the other format Digital Out Port. For clarity: Clock received at Coax In on the Ultralite will be expressed at the Optical Out port when the Ultralite is set to receive clock from its Coax In and vice-versa. Of course, whatever device is the Clock Master must be powered on and connected for the system to function.
The phrasing of your question has me wondering whether you hope to connect two
different external devices to the Coax SPDIF Ports simultaneously; one device to the Coax In and a second to the Coax Out. I am uncertain whether the the Coax SPDIF Out port will mirror the clock received on its corresponding Coax SPDIF In port. My guess is it would not, but if this is your desire, a call to MOTU should get you an answer, (or perhaps someone else will come in with the info.)