Interfacing
The DR-110 could output a "V-trig" clock pulse (+6V, 10ms duration), via a 3.5mm mini-jack, to allow other slave units (e.g. arpeggiators) to synchronize to its tempo.
The DR-110 has a 10kΩ impedance unbalanced mono audio output, available on an ¼" phone connector socket. The socket was configured as the "Roland P-bus", which meant it also could be used as a simultaneous audio input, the input source being mixed with the output signal.
A separate 3.5mm headphone output socket was also present.
Sync: The standard DR110 doesn't offer any kind of external sync, but can be fitted with third party DIN-sync interfaces available from circuitbenders.co.uk or Germany's acidlabs. Internally the DR110 runs at 12ppqn (pulses per quarter note) so extra circuitry is needed to interface it with the Roland DIN-sync standard of 24ppqn.
Test Mode: Press and hold down the Start and Stop buttons when you turn on your unit. The entire LED screen show. Press your blue buttons one at the time, a big OK appear in the programming grid after last button. Turn off and then on to exit test mode and go back to normal mode.
Read more about this topic: Boss Doctor Rhythm DR-110