Dave Smith Instruments PROPHET 08 DESKTOP - Manual (Page 60)

Packed Data Format
Data is packed in 8 byte “packets”, with the MS bit stripped from 7 parameter
bytes, and packed into an eighth byte, which is sent at the start of the 8 byte
packet.
Example:
Input Data
Packed MIDI data
1 A7 A6 A5 A4 A3 A2 A1 A0
1 00 G7 F7 E7 D7 C7 B7 A7
2 B7 B6 B5 B4 B3 B2 B1 B0 2 00 A6 A5 A4 A3 A2 A1 A0
3 C7 C6 C5 C4 C3 C2 C1 C0 3 00 B6 B5 B4 B3 B2 B1 B0
4 D7 D6 D5 D4 D3 D2 D1 D0 4 00 C6 C5 C4 C3 C2 C1 C0
5 E7 E6 E5 E4 E3 E2 E1 E0 5 00 D6 D5 D4 D3 D2 D1 D0
6 F7 E6 E5 E4 E3 E2 E1 E0 6 00 E6 E5 E4 E3 E2 E1 E0
7 G7 G6 G5 G4 G3 G2 G1 G0 7 00 F6 F5 F4 F3 F2 F1 F0
8 00 G6 G5 G4 G3 G2 G1 G0
This explains why it takes 439 MIDI bytes to transmit 384 Program data bytes.
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