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Example of an Exclusive message and calculating a
Checksum
Roland Exclusive messages 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> Setting REVERB MACRO to ROOM 3
According to the "Parameter Address Map," the REVERB MACRO Address is 40 01 30H,
and ROOM 3 is a value of 02H. Thus,
F0
41
10
42
12
(1)
(2)
(3)
(4)
(5)
(1) Exclusive Status, (2) ID (Roland), (3) Device ID (17),
(4) Model ID (GS), (5) Command ID (DT1), (6) End of Exclusive
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.
About tuning
In MIDI, individual Parts are tuned by sending RPN #1 (Master Fine Tuning) to the appro-
priate MIDI channel.
In MIDI, an entire device is tuned by either sending RPN #1 to all MIDI channels being
used, or by sending a System Exclusive MASTER TUNE (address 40 00 00H).
RPN #1 allows tuning to be specified in steps of approximately 0.012 cents (to be precise,
100/8192 cent), and System Exclusive MASTER TUNE allows tuning in steps of 0.1 cent.
One cent is 1/100th of a semitone.
The values of RPN #1 (Master Fine Tuning) and System Exclusive MASTER TUNE are
added together to determine the actual pitch sounded by each Part.
Frequently used tuning values are given in the following table for your reference. Values
are in hexadecimal (decimal in parentheses).
+————————+————————+——————————————+———————————————————+
|Hz in A4|
cent
| RPN #1 | Sys.Ex. 40 00 00
+————————+————————+——————————————+———————————————————+
|
445.0 | +19.56 | 4C 43 (+1603)| 00 04 0C 04 (+196)|
|
444.0 | +15.67 | 4A 03 (+1283)| 00 04 09 0D (+157)|
|
443.0 | +11.76 | 47 44 (+ 964)| 00 04 07 06 (+118)|
|
442.0 | + 7.85 | 45 03 (+ 643)| 00 04 04 0F (+ 79)|
|
441.0 | + 3.93 | 42 42 (+ 322)| 00 04 02 07 (+ 39)|
|
440.0 |0.00 | 40 00 ( 0)| 00 04 00 00 (0)|
|
439.0 | - 3.94 | 3D 3D (- 323)| 00 03 0D 09 (- 39)|
|
438.0 | - 7.89 | 3A 7A (- 646)| 00 03 0B 01 (- 79)|
+————————+————————+——————————————+———————————————————+
<Example> Set the tuning of MIDI channel 3 to A4 = 442.0 Hz
Send RPN#1 to MIDI channel 3. From the above table, the value is 45 03H.
B2
64 00
MIDI ch.3, lower byte of RPN parameter number: 00H
(B2)
65 01
(MIDI ch.3) upper byte of RPN parameter number: 01H
(B2)
06 45
(MIDI ch.3) upper byte of parameter value: 45H
(B2)
26 03
(MIDI ch.3) lower byte of parameter value: 03H
(B2)
64 7F
(MIDI ch.3) lower byte of RPN parameter number: 7FH
(B2)
65 7F
(MIDI ch.3) upper byte of RPN parameter number: 7FH
40 01 30
02
??
Address
data
Checksum
|
The Scale Tune Feature (address: 40 1x 40)
The scale Tune feature allows you to finely adjust the individual pitch of the notes from C
through B. Though the settings are made while working with one octave, the fine adjust-
ments will affect all octaves. By making the appropriate Scale Tune settings, you can obtain
a complete variety of tuning methods other than equal temperament. As examples, three
possible types of scale setting are explained below.
Equal Temperament
This method of tuning divides the octave into 12 equal parts. It is currently the most widely
used form of tuning,
especially in occidental music. On AT-90R, the default settings for the Scale Tune feature
produce equal temperament.
Just Temperament (Keytone C)
The three main chords resound much more beautifully than with equal temperament, but
this benefit can only be obtained in one key. If transposed, the chords tend to become
ambiguous. The example given involves settings for a key in which C is the keynote.
Arabian Scale
By altering the setting for Scale Tune, you can obtain a variety of other tunings suited for
ethnic music. For example, the settings introduced below will set the unit to use the Arabian
F7
Scale.
(6)
Example Settings
Note name
Equal Temperament
C
0
C#
0
D
0
D#
0
E
0
F
0
F#
0
G
0
G#
0
A
0
A#
0
B
0
The values in the table are given in cents. Refer to the explanation of Scale Tuning to convert
these values to hexadecimal, and transmit them as exclusive data.
For example, to set the tune (C-B) of the Part1 Arabian Scale, send the data as follows:
F0 41 10 42 12 40 11 40 3A 6D 3E 34 0D 38 6B 3C 6F 40 36 0F 50 F7
Just Temperament (Keytone C)
Arabian Scale
0
-6
-8
+45
+4
-2
+16
-12
-14
-51
-2
-8
-10
+43
+2
-4
+14
+47
-16
0
+14
-10
-12
-49
153
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