Edirol UR-80 Manual Del Usuario página 384

MIDI implementation
4. Supplementary material
Decimal and Hexadecimal table
(An "H" is appended to the end of numbers in hexadecimal notation.)
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.
fig.11-22e
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
* The decimal expression of the MIDI channel, program change, etc., is one
greater than the decimal value shown in the table above.
* The hexadecimal expression for each 7 bits allows a maximum of 128 steps (0--
127) to be expressed by one byte of data. Multiple bytes are used if the data
requires greater resolution than this. For example, a value expressed by two 7-
bit bytes "aa" and "bbH" would be aa x 128 + bb.
* In the case of signed (+/-) data, 00H = -64, 40H = +/-0, and 7FH = +63; i.e., a
value 64 less than the decimal value shown in the above table is used. In the case
of a two-byte value, 00 00H = -8192, 40 00 = +/-0, and 7F 7F = +8191. For
example, a value of "aa" and "bbH" would have a decimal expression of aa bbH
- 40 00H = aa x 128 + bb - 64 x 128.
* In the case of data indicated as "use nibble data," hexadecimal expression in 4-
bit units is used. A nibble-expressed value of the two bytes 0a and 0bH would
have a value of a x 16 + b.
<Example1>
What is the decimal expression of 5AH?
From the preceding table, 5AH = 90.
<Example2>
What is the decimal expression of the 7-bit hexadecimal value 12 34H?
From the preceding table, 12H = 18, and 34H = 52.
Thus, this is 18 x 128 + 52 = 2356
<Example3>
What is the decimal expression of the nibble-expressed value 0A 03 09 0D?
From the preceding table, 0AH = 10, 03H = 3, 09H = 9, and 0DH = 13.
Thus, this is ((10 x 16 + 3) x 16 + 9) x 16 + 13 = 41885
<Example4> What is the nibble-expressed value of decimal 1258?
1258 ÷ 16 = 78 (quotient) ... 10 (remainder)
78 ÷ 16 = 4 (quotient) ... 14 (remainder)
4 ÷ 16 = 0 (quotient) ... 4 (remainder)
From the preceding table, 0 = 00H, 4 = 04H, 14 = 0EH, 10 = 0HA.
Thus, the nibble-expressed value is
384
Hex. Dec. Hex. Dec. Hex.
20H 64 40H 96 60H
21H 65 41H 97 61H
22H 66 42H 98 62H
23H 67 43H 99 63H
24H 68 44H 100 64H
25H 69 45H 101 65H
26H 70 46H 102 66H
27H 71 47H 103 67H
28H 72 48H 104 68H
29H 73 49H 105 69H
2AH 74 4AH 106 6AH
2BH 75 4BH 107 6BH
2CH 76 4CH 108 6CH
2DH 77 4DH 109 6DH
2EH 78 4EH 110 6EH
2FH 79 4FH 111 6FH
30H 80 50H 112 70H
31H 81 51H 113 71H
32H 82 52H 114 72H
33H 83 53H 115 73H
34H 84 54H 116 74H
35H 85 55H 117 75H
36H 86 56H 118 76H
37H 87 57H 119 77H
38H 88 58H 120 78H
39H 89 59H 121 79H
3AH 90 5AH 122 7AH
3BH 91 5BH 123 7BH
3CH 92 5CH 124 7CH
3DH 93 5DH 125 7DH
3EH 94 5EH 126 7EH
3FH 95 5FH 127 7FH
00 04 0E 0AH
Example of an actual MIDI message
<Example1> CE 04
CnH is the Program Change status. "n" is the MIDI channel number. EH = 14, and
04H = 04. Thus, this is a program change message on MIDI channel 15, for program
number 05.
Checksum calculation
In order to verify that the message was received correctly, Roland exclusive
messages (RQ1, DT1) add a checksum following the end of the data (before the F7).
The checksum value is determined by the address and data (or size) of the
exclusive message that is transmitted.
Calculating the checksum
("H" has been added following hexadecimal values)
The checksum is a value that results in a lower 7 bits of 0 when the address, size,
and checksum itself are added together.
Specifically, the calculation will be as follows when the exclusive message you
want to transmit has an address of aa bb ccH and data or size of dd ee ffH.
aa + bb + cc + dd + ee + ff = total
total ÷ 128 = quotient ... remainder
128 - remainder = checksum
* However, as an exception, the checksum for a remainder of 0 is not 80H but
rather 00H.