There is cryptic information in the back of the JV-1080 manual explaining how to control the 1080 with SysEx messages. Unless you're a programmer, this stuff is pretty useless. Here is what I could figure out:
Set to Performance Mode:
F0 41 10 6A 12 00 00 00 00 00 00 F7
Set to Patch Mode:
F0 41 10 6A 12 00 00 00 00 01 7F F7
Set to GM Mode:
F0 41 10 6A 12 00 00 00 00 02 7E F7
I couldn't seem to find any mention of setting the 1080 to Rhythm Mode though. If you've seen it done by some software, let me know because I'm interested too. If it can't be set to Rythm Mode and you are trying to program a patch editor or something, you can still set rythm parameters without switching to rythm mode. The mode only changes what is displayed on the front panel, it doesn't effect what SysEx information can be received.
Another interesting thing to note is that you can't send the 1080 SysEx messages after you put it in GM Mode because it is forced to behave as a true GM instrument, which would not understand 1080 SysEx messages. So you can't set it back to Performance or Patch mode until you manually switch out of GM mode from the front panel.
Hopefully that helps...
If you are interested in how I derived those SysEx bytes, let me know and I will explain.
Mitch
The Sonic Spot