User guide

Chapter 7: MIDI Messages Defined
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Axiom User Guide
16,384 Step Resolution Through Combined Coarse and Fine Messages
Most assignable MIDI controls, including those on Axiom, operate with a resolution of 128 steps. Standard
MIDI CC messages that can be used universally between different MIDI devices are also limited to a resolution
of 128 steps. However, the RPN/NRPN concept provides a resolution of 16,384 steps by combining two 7-bit
MIDI messages into a 14-bit message (coarse + fine).
Hardware controller knobs or faders that take advantage of the full 14-bit RPN/NRPN resolution are very un-
common. To illustrate the concept and make the purpose of RPN/NRPN Coarse and Fine messages easier to
understand, the following diagram describes how such a 14-bit RPN/NRPN control would operate (not sup-
ported by Axiom):
The RPN/NRPN coarse message divides the range of 16384 steps into 128 segments and activates them by
sending each segment's first value, while the RPN/NRPN fine message provides the 128 steps of resolution
contained in each of these segments.
Coarse
9
8
7
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4
3
2
1
0
16,384
127
9
8
7
6
5
4
3
2
1
0
127
9
8
7
6
5
4
3
2
1
0
127
3
9
8
7
6
6
5
5
5
5
4
4
4
4
3
3
3
9
8
7
6
6
5
5
5
5
4
4
4
4
3
3
9
8
7
6
6
5
5
5
5
4
4
4
4
3
3
1
2
0
Fine
Fine
Fine
16,384
0