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EXR-5/EXR-3 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.

• Decimal values such as MIDI channel, bank select, and program change are listed

as one greater than the values given in the above table.

• A 7-bit byte can express data in the range of 128 steps. For data where greater pre-

cision 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.

• Data marked “Use nibbled data” is expressed in hexadecimal in 4-bit units. A value

expressed as a 2-byte nibble 0a 0bH has the value of a x 16+b.

[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

[Example 3] What is the decimal expression of the nibbled value 0A 03 09 0D?

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

((10 x 16+3) x 16+9) x 16+13 = 41885

[Example 4] What is the nibbled expression of the decimal value 1258?

Since from the preceding table, 0 = 00H, 4 = 04H, 14 = 0EH, 10 = 0AH, 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 with MIDI CH = 3, note number 62 (note name

is 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 with MIDI CH = 15, program number

74 (Flute in GS).

[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 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

If the Pitch Bend Sensitivity is set to 2 semitones, -8192 (00 00H) will cause the pitch

to change by -200 cents, so in this case -200 x (-3072) ÷ (-8192) = -75 cents of Pitch

Bend is being applied to MIDI channel 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. For Control

Changes, the 2nd byte is the control number, and the 3rd byte is the value. In a case

in which two or more consecutive messages have the same status, MIDI has a provi-

sion called “running status” which allows the status byte of the second and following

messages to be omitted. Thus, the above messages have the following meaning.

In other words, the above messages specify a value of 0C 00H for RPN parameter

number 00 00H on MIDI channel 4, and then set the RPN parameter number to 7F

7FH.

RPN parameter number 00 00H is Pitch Bend Sensitivity, and the MSB of the value

indicates semitone units, so a value of 0CH = 12 sets the maximum pitch bend range

to +/-12 semitones (1 octave). (On GS sound generators the LSB of Pitch Bend Sen-

sitivity is ignored, but the LSB should be transmitted anyway (with a value of 0) so that

operation will be correct on any device.)

Once the parameter number has been specified for RPN or NRPN, all Data Entry mes-

sages transmitted on that same channel will be valid, so after the desired value has

been transmitted, it is a good idea to set the parameter number to 7F 7FH to prevent

accidents. This is the reason for the (B3) 64 7F (B3) 65 7F at the end.

It is not desirable for performance data (such as Standard MIDI File data) to contain

many events with running status as given in [Example 4]. 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 generator will then misinterpret

the data. Take care to give each event its own status.

It is also necessary that the RPN or NRPN parameter number setting and the value set-

ting be done in the proper order. On some sequencers, 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

■ Example of an Exclusive message and calculating

a checksum

Roland Exclusive messages (RQ1, DT1) are transmitted with a checksum at the end

(before F7) to make sure that the message was correctly received. The value of the

checksum is determined by the address and data (or size) of the transmitted Exclusive

message.

❍

How to calculate the checksum (hexadecimal numbers are indicated by “H”)

The checksum is a value derived by adding the address, size, and checksum itself and

inverting the lower 7 bits.

Here’s an example of how the checksum is calculated. We will assume that in the

Exclusive message we are transmitting, the address is aa bb ccH and the data or size

is dd ee ffH.

aa+bb+cc+dd+ee+ff = sum

sum ÷ 128 = quotient ... remainder

128 - remainder = checksum

[Example 1] Setting REVERB MACRO to ROOM 3

According to the “Parameter Address Map (p.247),” the REVERB MACRO Address is

40 01 30H, and ROOM 3 is a value of 02H. Thus:

Next, we calculate the checksum.

40H+01H+30H+02H = 64+1+48+2 = 115 (sum)

115 (sum) ÷ 128 = 0 (quotient) ... 115 (remainder)

checksum = 128 - 115 (remainder) = 13 = 0DH

This means that F0 41 10 42 12 40 01 30 02 0D F7 is the message we transmit.

[Example 2] Setting REVERB LEVEL to 12

16) 1258

16) 78 ... 10

16) 4 ... 14

0 ... 4

Dec. Hex. Dec. Hex. Dec. Hex. Dec. Hex.

00H

01H

02H

03H

04H

05H

06H

07H

08H

09H

0AH

0BH

0CH

0DH

0EH

0FH

10H

11H

12H

13H

14H

15H

16H

17H

18H

19H

1AH

1BH

1CH

1DH

1EH

1FH

20H

21H

22H

23H

24H

25H

26H

27H

28H

29H

2AH

2BH

2CH

2DH

2EH

2FH

30H

31H

32H

33H

34H

35H

36H

37H

38H

39H

3AH

3BH

3CH

3DH

3EH

3FH

40H

41H

42H

43H

44H

45H

46H

47H

48H

49H

4AH

4BH

4CH

4DH

4EH

4FH

50H

51H

52H

53H

54H

55H

56H

57H

58H

59H

5AH

5BH

5CH

5DH

5EH

5FH

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

60H

61H

62H

63H

64H

65H

66H

67H

68H

69H

6AH

6BH

6CH

6DH

6EH

6FH

70H

71H

72H

73H

74H

75H

76H

77H

78H

79H

7AH

7BH

7CH

7DH

7EH

7FH

B3 64 00 MIDI ch.4, lower byte of RPN parameter number: 00H

(B3) 65 00 (MIDI ch.4) upper byte of RPN parameter number: 00H

(B3) 06 0C (MIDI ch.4) upper byte of parameter value: 0CH

(B3) 26 00 (MIDI ch.4) lower byte of parameter value: 00H

(B3) 64 7F (MIDI ch.4) lower byte of RPN parameter number: 7FH

(B3) 65 7F (MIDI ch.4) upper byte of RPN parameter number: 7FH

F0 41 10 42 12 40 01 30 02 ?? F7

(1) (2) (3) (4) (5) address data checksum (6)

(1) Exclusive Status, (2) ID (Roland), (3) Device ID (17),

(4) Model ID (GS), (5) Command ID (DT1), (6) End of Exclusive