We've just posted a draft of the User Manual and we would like to know if you can find the answer to your questions there. If not, we need to add that to the manual and would appreciate your input!
MRCC Draft User Manual
To answer your question, the 12 ports available on the PC MIDI Interface connection are 12 independent inputs and 12 independent outputs on the MRCC, and also appear as 12 independent inputs and 12 independent outputs on the PC. You can route from any inputs to any outputs.
We don't really have a good excuse to include this many USB MIDI virtual ports on the PC interface, it would be great to know if anyone has a use case for this. Our only use case is using independent USB MIDI virtual outputs from MRCC to standalone soft-synths which on a Windows PC can't share ports. We aren't DAW experts, but we've seen evidence that using MIDI channels in a DAW is prefered to using independant virtual ports.
While we are on the topic, each of the MRCC host ports have 4 USB MIDI virtual inputs, and 1 USB MIDI virtual output. We did not see a use case for multiple virtual outputs, though we have discovered 1 device (besides other MIDI routers) with 2 USB MIDI virtual inputs, the Korg SQ-1.
MRCC Draft User Manual
To answer your question, the 12 ports available on the PC MIDI Interface connection are 12 independent inputs and 12 independent outputs on the MRCC, and also appear as 12 independent inputs and 12 independent outputs on the PC. You can route from any inputs to any outputs.
We don't really have a good excuse to include this many USB MIDI virtual ports on the PC interface, it would be great to know if anyone has a use case for this. Our only use case is using independent USB MIDI virtual outputs from MRCC to standalone soft-synths which on a Windows PC can't share ports. We aren't DAW experts, but we've seen evidence that using MIDI channels in a DAW is prefered to using independant virtual ports.
While we are on the topic, each of the MRCC host ports have 4 USB MIDI virtual inputs, and 1 USB MIDI virtual output. We did not see a use case for multiple virtual outputs, though we have discovered 1 device (besides other MIDI routers) with 2 USB MIDI virtual inputs, the Korg SQ-1.