Roland Audio Canvas UA-100 User Manual page 88

MIDI Implementation
4. Supplementary Material
Decimal and Hexadecimal table
In MIDI documentation, data values and addresses/sizes of Exclusive messages etc.
are expressed as hexadecimal values for each 7 bits. The following table shows how
these correspond to decimal numbers.
Decimal and Hexadecimal table(An "H" is appended to the end of numbers in
hexadecimal notation.)
Dec. Hex. Dec.
0 00H 32
1 01H 33
2 02H 34
3 03H 35
4 04H 36
5 05H 37
6 06H 38
7 07H 39
8 08H 40
9 09H 41
10 0AH 42
11 0BH 43
12 0CH 44
13 0DH 45
14 0EH 46
15 0FH 47
16 10H 48
17 11H 49
18 12H 50
19 13H 51
20 14H 52
21 15H 53
22 16H 54
23 17H 55
24 18H 56
25 19H 57
26 1AH 58
27 1BH 59
28 1CH 60
29 1DH 61
30 1EH 62
31 1FH 63
* Decimal values such as MIDI channel, Bank Select, and Program Change are
listed as one greater than the values given in the above table.
* 7-bit byte can express data in the range of 128 steps. For data where greater
precision is required, we must use two or more bytes.
For example, two hexadecimal numbers aa bbH expressing two 7-bit bytes would
indicate a value of aa x 128 + bb.
* In the case of values which have a +/- sign, 00H = -64, 40H = +/-0, and 7FH =
+63, so that the decimal expression would be 64 less than the value given in the
above chart.
In the case of two types, 00 00H = -8192, 40 00H = +/-0, and 7F 7FH = +8191. For
example if aa bbH were expressed as decimal, this would be aa bbH - 40 00H = aa
x 128 + bb - 64 x 128.
<Example 1> What is the decimal expression of 5AH?
From the preceding table, 5AH = 90
<Example 2> What is the decimal expression of the value 12 34H given as
hexadecimal for each 7 bits?
From the preceding table, since 12H = 18 and 34H = 52
18 x 128 + 52 = 2356
88
Hex. Dec. Hex. Dec.
20H 64 40H 96
21H 65 41H 97
22H 66 42H 98
23H 67 43H 99
24H 68 44H 100
25H 69 45H 101
26H 70 46H 102
27H 71 47H 103
28H 72 48H 104
29H 73 49H 105
2AH 74 4AH 106
2BH 75 4BH 107
2CH 76 4CH 108
2DH 77 4DH 109
2EH 78 4EH 110
2FH 79 4FH 111
30H 80 50H 112
31H 81 51H 113
32H 82 52H 114
33H 83 53H 115
34H 84 54H 116
35H 85 55H 117
36H 86 56H 118
37H 87 57H 119
38H 88 58H 120
39H 89 59H 121
3AH 90 5AH 122
3BH 91 5BH 123
3CH 92 5CH 124
3DH 93 5DH 125
3EH 94 5EH 126
3FH 95 5FH 127
Examples of actual MIDI messages
<Example 1> E1 00 28
EnH is the Pitch Bend Change status, and n is the MIDI channel number. The 2nd
byte (00H = 0) is the LSB and the 3rd byte (28H = 40) is the MSB, but Pitch Bend
value is a signed number in which 40 00H (= 64 x 12 + 80 = 8192) is 0, so this Pitch
Bend value is
28 00H - 40 00H = 40 x 12 + 80 - (64 x 12 + 80) = 5120 - 8192 = -3072
Hex.
If the Pitch Bend Sensitivity is set to 2 semitones, -8192 (00 00H) will cause the pitch
60H
to change -200 cents, so in this case -200 x (-3072) / (-8192) = -75 cents of Pitch Bend is
61H
being applied to MIDI channel 2.
62H
63H
<Example 2> B1 64 00 65 00 06 0C 26 00 64 7F 65 7F
64H
65H
BnH is the Control Change status, and n is the MIDI channel number. For Control
66H
Changes, the 2nd byte is the Controller number, and the 3rd byte is the value. In a
67H
case in which two or more messages consecutive messages have the same status,
68H MIDI has a provision called running status which allows the status byte of the
second and following messages to be omitted. Thus, the above messages have the
69H
following meaning.
6AH
6BH
B1 64 00
6CH
(B1) 65 00
6DH
(B1) 06 0C
6EH
(B1) 26 00
6FH
(B1) 64 7F
70H
(B1) 65 7F
71H
In other words, the above messages specify a value of 0C 00H for RPN parameter
72H
number 00 00H on MIDI channel 2, and then set the RPN parameter number to 7F
73H
7FH.
74H
75H
RPN parameter number 00 00H is Pitch Bend Sensitivity, and the MSB of the value
76H
indicates semitone units, so a value of 0CH = 12 sets the maximum Pitch Bend range
77H
to +/-12 semitones (1 octave). (On UA-100 the LSB of Pitch Bend Sensitivity is
78H
ignored, but the LSB should be transmitted anyway (with a value of 0) so that
79H
operation will be correct on any device.)
7AH
Once the parameter number has been specified for RPN, all Data Entry messages
7BH
transmitted on that same channel will be valid, so after the desired value has been
7CH
transmitted, it is a good idea to set the parameter number to 7F 7FH to prevent
7DH
accidents. This is the reason for the (B3) 64 7F (B3) 65 7F at the end.
7EH
7FH
It is not desirable for performance data (such as Standard MIDI File data) to contain
many events with running status as given in <Example 2>. This is because if
playback is halted during the song and then rewound or fast-forwarded, the
sequencer may not be able to transmit the correct status, and the sound source will
then misinterpret the data. Take care to give each event its own status.
It is also necessary that the RPN parameter number setting and the value setting be
done in the proper order. On some sequencer software, events occurring in the same
(or consecutive) clock may be transmitted in an order different than the order in
which they were received. For this reason it is a good idea to slightly skew the time
of each event (about 1 tick for TPQN = 96, and about 5 ticks for TPQN = 480).
* TPQN: Ticks Per Quarter Note
MIDI ch.2, lower byte of RPN parameter number:
(MIDI ch.2) upper byte of RPN parameter number:
(MIDI ch.2) upper byte of parameter value:
(MIDI ch.2) lower byte of parameter value:
(MIDI ch.2) lower byte of RPN parameter number:
(MIDI ch.2) upper byte of RPN parameter number:
00H
00H
0CH
00H
7FH
7FH