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203

MIDI Implementation

Appendices

■ Decimal/Hexadecimal Table (hexadecimal values

are indicated by a following “H”)

MIDI uses 7-bit hexadecimal values to indicate data values and the address and size of

exclusive messages. The following table shows the correspondence between decimal and

hexadecimal numbers.

+——————+——————++——————+——————++——————+——————++——————+——————+

| D | H || D | H || D | H || D | H |

+——————+——————++——————+——————++——————+——————++——————+——————+

| 0 | 00H || 32 | 20H || 64 | 40H || 96 | 60H |

| 1 | 01H || 33 | 21H || 65 | 41H || 97 | 61H |

| 2 | 02H || 34 | 22H || 66 | 42H || 98 | 62H |

| 3 | 03H || 35 | 23H || 67 | 43H || 99 | 63H |

| 4 | 04H || 36 | 24H || 68 | 44H || 100 | 64H |

| 5 | 05H || 37 | 25H || 69 | 45H || 101 | 65H |

| 6 | 06H || 38 | 26H || 70 | 46H || 102 | 66H |

| 7 | 07H || 39 | 27H || 71 | 47H || 103 | 67H |

| 8 | 08H || 40 | 28H || 72 | 48H || 104 | 68H |

| 9 | 09H || 41 | 29H || 73 | 49H || 105 | 69H |

| 10 | 0AH || 42 | 2AH || 74 | 4AH || 106 | 6AH |

| 11 | 0BH || 43 | 2BH || 75 | 4BH || 107 | 6BH |

| 12 | 0CH || 44 | 2CH || 76 | 4CH || 108 | 6CH |

| 13 | 0DH || 45 | 2DH || 77 | 4DH || 109 | 6DH |

| 14 | 0EH || 46 | 2EH || 78 | 4EH || 110 | 6EH |

| 15 | 0FH || 47 | 2FH || 79 | 4FH || 111 | 6FH |

| 16 | 10H || 48 | 30H || 80 | 50H || 112 | 70H |

| 17 | 11H || 49 | 31H || 81 | 51H || 113 | 71H |

| 18 | 12H || 50 | 32H || 82 | 52H || 114 | 72H |

| 19 | 13H || 51 | 33H || 83 | 53H || 115 | 73H |

| 20 | 14H || 52 | 34H || 84 | 54H || 116 | 74H |

| 21 | 15H || 53 | 35H || 85 | 55H || 117 | 75H |

| 22 | 16H || 54 | 36H || 86 | 56H || 118 | 76H |

| 23 | 17H || 55 | 37H || 87 | 57H || 119 | 77H |

| 24 | 18H || 56 | 38H || 88 | 58H || 120 | 78H |

| 25 | 19H || 57 | 39H || 89 | 59H || 121 | 79H |

| 26 | 1AH || 58 | 3AH || 90 | 5AH || 122 | 7AH |

| 27 | 1BH || 59 | 3BH || 91 | 5BH || 123 | 7BH |

| 28 | 1CH || 60 | 3CH || 92 | 5CH || 124 | 7CH |

| 29 | 1DH || 61 | 3DH || 93 | 5DH || 125 | 7DH |

| 30 | 1EH || 62 | 3EH || 94 | 5EH || 126 | 7EH |

| 31 | 1FH || 63 | 3FH || 95 | 5FH || 127 | 7FH |

+——————+——————++——————+——————++——————+——————++——————+——————+

D: decimal

H: hexadecimal

* Decimal expressions such as used for MIDI channel, Bank Select, and Program Change

will be the value 1 greater than the decimal value given in the above table.

* Since each MIDI byte carries 7 significant data bits, each byte can express a maximum of

128 different values. Data for which higher resolution is required must be transmitted

using two or more bytes. For example a value indicated as a two-byte value of aa bbH

would have a value of aa x 128 + bb.

* For a signed number (+/-), 00H = -64, 40H = +/-0, and 7FH = +63. I.e., the decimal

equivalent will be 64 less than the decimal value given in the above table. For a two-byte

signed number, 00 00H = -8192, 40 00H = +/-0, and 7F 7FH = +8191. For example the

decimal expression of aa bbH would be aa bbH - 40 00H = (aa x 128 + bb - 64 x 128.

* Hexadecimal notation in two 4-bit units is used for data indicated as “nibbled”. The

nibbled two-byte value of 0a 0b H would be a x 16 + b.

<Example 1> What is the decimal equivalent of 5AH?

From the above table, 5AH = 90.

<Example 2> What is the decimal equivalent of the 7-bit hexadecimal values 12 34H?

From the above table, 12H = 18 and 34H = 52

Thus, 18 x 128 + 52 = 2356

<Example 3> What is the decimal equivalent of the nibbled expression 0A 03 09 0DH?

From the above table, 0AH = 10, 03H = 3, 09H = 9, 0DH = 13

Thus, the result is ((10 x 16 + 3) x 16 + 9) x 16 + 13 = 41885

<Example 4> What is the nibbled equivalent of the decimal number 1258?

16 ) 1258

16 ) 78...10

16 ) 4...14

0... 4

From the above table, 0=00H, 4=04H, 14=0EH, 10=0AH

Thus the result is 00 04 0E 0AH

■ Examples of Actual MIDI Messages

<Example 1> 92 3E 5F

9n is the Note On status and `n' is the MIDI channel number. Since 2H = 2, 3EH = 62, and

5FH = 95, this is a Note On message of MIDI CH = 3, note number 62 (note name D4) and

velocity 95.

<Example 2> CE 49

CnH is the Program Change status and `n' is the MIDI channel number. Since EH = 14, and

49H = 73, this is a Program Change message of MIDI CH = 15, Program number 74 (in the

GS sound map, Flute).

<Example 3> EA 00 28

EnH is the Pitch Bend Change status and `n' is the MIDI channel number. The 2nd byte

(00H=0) is the LSB of the Pitch Bend value, and the 3rd byte (28H=40) is the MSB. However

since the Pitch Bend is a signed number with 0 at 40 00H ( = 64 x 128 + 0 = 8192), the Pitch

Bend value in this case is

28 00H - 40 00H = 40 x 128 + 0 - (64 x 128 + 0) = 5120 - 8192 = -3072

If we assume that the Pitch Bend Sensitivity is set to two semitones, the pitch will change

only -200 cents for a Pitch Bend value of -8192 (00 00H). Thus, this message is specifying a

Pitch Bend of -200 x (-3072) / (-8192) = -75 cents on MIDI CH = 11.

<Example 4> B3 64 00 65 00 06 0C 26 00 64 7F 65 7F

BnH is the Control Change status, and `n' is the MIDI channel number. In Control Change

messages, the 2nd byte is the controller number, and the 3rd byte is the parameter value.

MIDI allows what is known as “running status,” when if messages of the the same status

follow each other, it is permitted to omit the second and following status bytes. In the

message above, running status is being used, meaning that the message has the following

content.

B3 64 00 MIDI CH = 4, RPN parameter number LSB: 00H

(B3) 65 00 MIDI CH = 4, RPN parameter number MSB: 00H

(B3) 06 0C MIDI CH = 4, parameter value MSB: 0CH

(B3) 26 00 MIDI CH = 4, parameter value LSB: 00H

(B3) 64 7F MIDI CH = 4, RPN parameter number LSB: 7FH

(B3) 65 7F MIDI CH = 4, RPN parameter number MSB: 7FH

Thus, this message transmits a parameter value of 0C 00H to RPN parameter number 00

00H on MIDI CH = 4, and then sets the RPN parameter number to 7F 7FH.

The function assigned to RPN parameter number 00 00H is Pitch Bend Sensitivity, and the

MSB of the parameter value indicates semitone steps. Since the MSB of this parameter value

is 0CH = 12, the maximum width of pitch bend is being set to [+-]12 semitones (1 octave)

(GS sound sources ignore the LSB of Pitch Bend Sensitivity, but it is best to transmit the LSB

(parameter value 0) as well, so that the message can be correctly received by any device.

Once the parameter number has been set for RPN or NRPN, all subsequent Data Entry

messages on that channel will be effective. Thus, it is recommended that after you have

made the change you want, you set the parameter number to 7F 7FH (an “unset” or “null”

setting). The final (B3) 64 7F (B3) 65 7F is for this purpose.

It is not a good idea to store many events within the data of a song (e.g., a Standard MIDI

File song) using running status as shown in <Example 4>. When the song is paused, fast-

forwarded or rewound, the sequencer may not be able to transmit the proper status, causing

the sound source to misinterpret the data. It is best to attach the proper status byte to all

events.

It is also important to transmit RPN or NRPN parameter number settings and parameter

values in the correct order. In some sequencers, data events recorded in the same clock (or a

nearby clock) can sometimes be transmitted in an order other than the order in which they

were recorded. It is best to record such events at an appropriate interval (1 tick at TPQN=96,

or 5 ticks at TPQN=480).

* TPQN: Ticks Per Quarter Note (i.e., the time resolution of the sequencer)

1 2 ... 198 199 200 201 202 203 204 205 206 207 208 ... 215 216

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Roland XP-60 Owner's Manual Page 203

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