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 cc ddH and the data or size is ee ffH.

aa+ bb + cc + dd + ee + ff = sum sum 128 = quotient ... remainder 128 - remainder = checksum

<Example1> Setting MFX Type of Performance Common MFX to OVERDRIVE (DT1)

According to the “Parameter Address Map” (p. 146), the start address of Temporary Performance is 10 00 00 00H, the offset address of Performance Common MFX is 02 00H, and the address of MFX Type is 00 00H. Therefore the address of MFX Type of Performance Common MFX is;

10 00 00 00H

02 00H

+) 00 00H 10 00 02 00H

OVERDRIVE has the value of 02H.

So the system exclusive message should be sent is;

F0

41

10

00 10

12

10 00 02 00

02

??

F7

(1)

(2)

(3)

(4)

(5)

address

data

checksum

(6)

(1) Exclusive Status

 

(2) ID (Roland)

(3) Device ID (17)

 

(4) Model ID (XV-2020)

(5) Command ID (DT1)

(6) End of Exclusive

 

Then calculate the checksum.

10H + 00H + 02H + 00H + 02H = 16 + 0 + 2 + 0 + 2 = 20 (sum) 20 (sum) 128 = 0 (quotient) ... 20 (remainder)

checksum = 128 - 20 (remainder) = 108 = 6CH

This means that F0 41 10 00 10 12 10 00 02 00 02 6C F7 is the message should be sent.

<Example2> Getting the data (RQ1) of Performance Part 3 in USER:03

According to the “Parameter Address Map” (p. 146), the start address of USER:03 is 20 02 00 00H, and the offset address of Performance Part 3 is 00 22 00H.

Therefore the start address of Performance Part 3 in USER:03 is;

20 02 00 00H

+) 00 22 00H 20 02 22 00H

As the size of Performance Part is 00 00 00 31H, the system exclusive message should be sent is;

F0

41

10

00 10

11

20 02 22 00

00 00 00 31

??

F7

(1)

(2)

(3)

(4)

(5)

address

data

checksum

(6)

(1) Exclusive Status

 

(2) ID (Roland)

(3) Device ID (17)

 

(4) Model ID (XV-2020)

(5) Command ID (RQ1)

(6) End of Exclusive

 

Then calculate the checksum.

20H + 02H + 22H + 00H + 00H + 00H + 00H + 31H = 32 + 2 + 34 + 0 + 0 + 0 + 0 + 49 = 117 (sum)

117 (sum) 128 = 0 (quotient) ... 117 (remainder) checksum = 128 - 117 (remainder) = 11 = 0BH

This means that F0 41 10 00 10 11 20 02 22 00 00 00 00 31 0B F7 is the message should be sent.

MIDI Implementation

<Example3> Getting Temporary Performance data (RQ1)

According to the “Parameter Address Map” (p. 146), the start address of Temporary Performance is assigned as following:

10 00 00 00H

Temporary Performance Common

:

 

10 00 20 00H

Temporary Performance Part 1

:

 

10 00 2F 00H

Temporary Performance Part 16

As the data size of Performance Controller is 00 00 00 31H, summation of the size and the start address of Temporary Performance Part 16 will be;

10

00

2F

00H

+) 00

00

00

31H

10

00

2F

31H

And the size that have to be got should be;

10

00

2F

31H

 

 

 

 

 

 

Implementation

 

 

 

 

 

 

 

-) 10

00 00

00H

 

 

 

 

 

 

 

00

00

2F

31H

 

 

 

 

 

 

 

Therefore the system exclusive message should be sent is;

 

 

 

 

F0

41

10

00 10

11 10 00 00 00

00 00 2F 31

??

F7

MIDI

 

(1)

(2)

(3)

(4)

(5) address

data

checksum

(6)

 

 

(1) Exclusive Status

 

(2) ID (Roland)

(3) Device ID (17)

 

 

 

 

 

(4) Model ID (XV-2020)

(5) Command ID (RQ1)

(6) End of Exclusive

 

 

Calculating the checksum as shown in <Example 2>, we get a message of F0 41 10 6A 11 10 00 00 00 00 00 2F 31 10 F7 to be transmitted.

<Example4> Getting data (RQ1) at once;

Temporary Performance data,

Temporary Patch data of whole part in Performance mode,

Temporary Rhythm data of whole part in Performance mode.

According to the “Parameter Address Map” (p. 146), the start address of the above all parameters is assigned as following:

10 00 00 00H

Temporary Performance

11 00 00 00H

Temporary Patch (Performance Mode Part 1)

11 10 00 00H

Temporary Rhythm (Performance Mode Part 1)

:

 

14 60 00 00H

Temporary Patch (Performance Mode Part 16)

14 70 00 00H

Temporary Rhythm (Performance Mode Part 16)

The offset address of Rhythm is also assigned as follows:

00 00 00H

Rhythm Common

:

 

00 10 00H

Rhythm Tone (Key # 21)

:

 

01 3E 00H

Rhythm Tone (Key # 108)

As the data size of Rhythm Tone is 00 00 01 41H, summation of the size and the start address of Temporary Rhythm Tone #108 in Performance mode will be;

14 70 00 00H

01 3E 00H +) 00 00 01 41H 14 71 3F 41H

And the size that have to be got should be;

14 71 3F 41H -) 10 00 00 00H 04 71 3F 41H

Therefore the system exclusive message should be sent is;

F0

41

10

00 10

11

10 00 00 00

04 71 3F 41

??

F7

(1)

(2)

(3)

(4)

(5)

address

data

checksum

(6)

(1) Exclusive Status

 

(2) ID (Roland)

(3) Device ID (17)

 

(4) Model ID (XV-2020)

(5) Command ID (RQ1)

(6) End of Exclusive

 

Calculating the checksum as shown in <Example 2>, we get a message of F0 41 10 00 10 11 10 00 00 00 04 71 3F 41 7B F7 to be transmitted.

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Kenwood XV-2020 owner manual 159, Example of an Exclusive Message Calculating a Checksum, How to calculate the checksum

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