Digital Control Bus

DCB (Digital Control Bus, Digital Connection Bus or Digital Communication Bus in some sources) was a proprietary data interchange interface by Roland Corporation, developed in 1981 and introduced in 1982 in their Roland Juno-60 and Roland Jupiter-8 products. DCB functions were basically the same as MIDI, but unlike MIDI (which is capable of transmitting a wide array of information), DCB could provide note on/off, program change and vcf/vca control only. DCB-to-MIDI adapters were produced for a number of early Roland products. The DCB interface was made in 2 variants, the earlier one used 20-pin sockets and cables, later switching to the 14-pin Amphenol DDK connector vaguely resembling a parallel port.

DCB was quickly replaced by MIDI in the early 1980s. The only DCB-equipped instruments produced were the Roland Jupiter-8 and Juno-60; Roland produced at least two DCB sequencers, the JSQ-60 and the MSQ-700. The latter was capable of saving eight sequences, or a total of 3000 notes, and was capable of transmitting and receiving data via MIDI (though it could not convert signals between DCB and MIDI, nor could it use both protocols simultaneously). Roland later released the MD-8, a rather large black box capable of converting MIDI signals to DCB and vice versa. While this allows note on/off to be sent to a Juno-60 by MIDI, the solution pales in comparison to the full MIDI implementation on the Juno-60's successor, the Roland Juno-106. A few companies offer similar conversion boxes to connect DCB instruments to regular MIDI systems for support of vintage synths in modern sound production environments.

Following information comes from the Roland Juno 60 Service Notes, First Edition, page 17-19.

DCB uses a special 14-wire connection. The first 7 consist of 3 wires in each direction plus a shared ground. The signals are standard TTL 0-5V, except the Rx Busy output, which is an open collector pulldown.

1. Rx Busy 2. Rx Data 3. Rx Clock 4. Ground 5. Tx Busy 6. Tx Data 7. Tx Clock

The remaining 7 wires may be used for special purposes.

8. Unreg 9. VCA Lower 10. VCA Upper 11. VCF Lower 12. VCF upper 13. VCO-2 14. VCO-1

These are not used in the Juno 60.

View from rear panel. Amphenol DDK connector.

The DCB is a standard asynchronous serial stream (using an 8251A IC in the Juno 60), LSB first, 8 data bits, 2 stop bits, odd parity, and a Baud rate of 31.25 kHz.

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