7-Bit Data Packing - M-Audio Black Box User Manual

7-Bit Data Packing

The general data packing scheme for Preset and Drumbeat Data Dumps groups 7 bytes of data, stripping off the MS bit of each, and
packing these MS bits into an additional byte. 7 bytes of internal memory yields 8 bytes of MIDI data.
Assuming 7 bytes of memory data are:
0: AAAAaaaa Memory byte 0
1: BBBBbbbb Memory byte 1
2: CCCCcccc Memory byte 2
3: DDDDdddd Memory byte 3
4: EEEEeeee Memory byte 4
5: FFFFffff Memory byte 5
6: GGGGgggg Memory byte 6
Then it is sent over MIDI with the MS bits first as follows:
0: 0GFEDCBA Packed MS bits
1: 0AAAaaaa MIDI Data Bytes
2: 0BBBbbbb
3: 0CCCcccc
4: 0DDDdddd
5: 0EEEeeee
6: 0FFFffff
7: 0GGGgggg
Note that fewer than 7 bytes can be sent, and the unused MS bits will be set to zero. For example, if two bytes are sent:
Assuming 2 bytes of memory data are:
0: AAAAaaaa Memory byte 0
1: BBBBbbbb Memory byte 1
Then it is sent over MIDI as a three-byte sequence, with the MS bits first as follows:
0: 000000BA Packed MS bits
1: 0AAAaaaa MIDI Data Bytes
2: 0BBBbbbb
User Guide 55
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