Following information comes from the Roland JUNO-60 Service Notes, First Edition, pages 17–19.
Physical connection DCB uses a 14-wire connection. The first 7 consist of 3 wires in each direction plus a shared ground. The signals are standard 5V TTL, 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.
Pinout View of Amphenol DDK connector from rear panel. 7 6 5 4 3 2 1 14 13 12 11 10 9 8
Serial data format 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
kilobaud.
Message (Block) Structure DCB data is sent in short blocks messages consisting of an identifier, one or more data codes, and an end mark. Blocks may be sent intermittently (JP-8, OP-8) or continuously (JUNO-60), in which case end marks are not used. The identifier is 1 byte using a value F1 through FE, which acts as both a start marker and a message type. Data which follows must not use these data bytes. In practice only FD (patch code) and FE (key code) are used. Data codes are one or more sections or channels, each one byte. The number of bytes or channels depends on the transmitter's configuration, but does not change once communication has been started. All data values must be in the range 00–F0. The end mark is an FF character. It is omitted if the message has a predefined length or the next message starts immediately after the data.
FD: Patch Code Block This message identifies a patch, by a single byte. JUNO-60 ignores this. It is sent once after a patch change, with the first key code by OP-8 and JP-8. It does not have an end mark.
FE: Key Code This message identifies a key event. It contains one byte for each note channel the transmitter supports, so 8 bytes for JP-8 and OP-8, or 6 bytes for JUNO-60. Each channel byte defines a key number (bits 0–6) and whether the key is gated on (1) or off (bit 7). Keys are identified with 0–96 with zero meaning C0 (16.4 Hz), up to 96 C8 (4205 Hz). Channels are assigned in the order defined by the transmitter's key assign mode. For OP-8, this is Ch1–Ch8. For JP-8 split mode, Upper 4 keys followed by Lower 4 keys. In JP-8 dual mode, the data for the first 4 channels is duplicated to the second 4. If the JUNO-60 receives more channels than it physically has voices, the extra channels are "queued" and played later when possible. The JP-8 only accepts 8 channels. == References ==