I have the midi out from my Roland TD-7 going into the Midi In on the MD.
I have Midi Thru checked under MISC.
When I connect the midi cable to the Midi In on MD my trigger light stays solid red and I don't get any midi data, not from the drums connected to MD or the TD-7.
I also tried enabling Midi Thru in the Options menu, still nothing.
I couldn't find any documentation on how to set this up.