Roland XP-30 owner manual 204, Examples of Exclusive Messages Calculating the Checksum

MIDI Implementation

■Examples of Exclusive Messages and

Calculating the Checksum

Roland exclusive messages (RQ1, DT1) are transmitted with a checksum at the end of the data (before F7) to check that the data was received correctly. The value of the checksum is determined by the address and data (or size) of the exclusive message.

●How to Calculate the Checksum

(hexadecimal values are indicated by a “H”)

The checksum consists of a value whose lower 7 bits are 0 when the address, size and checksum itself are added.

The following formula shows how to calculate the checksum when the exclusive message to be transmitted has an address of aa bb cc ddH, and data or size of ee ffH.

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

<Example 1> Setting the Performance Common REVERB TYPE to DELAY (DT1)

The “Parameter address map” indicates that the starting address of the Temporary Performance is 01 00 00 00H, that the Performance Common offset address is 00 00H, and that the REVERB TYPE address is 00 28H. Thus, the address is:

01 00 00 00H

00 00H

+) 00 28H 01 00 00 28H

Since DELAY is parameter value 06H,

F0	41	10	6A	12	01 00 00 28	06	??	F7
(1)	(2)	(3)	(4)	(5)	address	data	checksum	(6)
(1) Exclusive status			(2) ID number (Roland)			(3) Device ID (17)
(4) Model ID (XP-30)			(5) Command ID (DT1)			(6) EOX

Next we calculate the checksum.

01H + 00H + 00H + 28H + 06H = 1 + 0 + 0 + 40 + 6 = 47 (sum) 47 (total) / 128 = 0 (quotient) ... 47 (remainder)

checksum = 128 - 47 (quotient) = 81 = 51H

This means that the message transmitted will be F0 41 10 6A 12 01 00 00 28 06 51 F7.

<Example 2> Retrieving data for USER:03 Performance Part 3 (RQ1)

The “Parameter Address Map” indicates that the starting address of USER:03 is 10 02 00 00H, and that the offset address of Performance Part 3 is 12 00H. Thus, the address is:

10 02 00 00H

+) 12 00H 10 02 12 00H

Since the size of the Performance Part is 00 00 00 19H,

F0	41	10	6A	11	10 02 12 00	00 00 00 19	??	F7
(1)	(2)	(3)	(4)	(5)	address	size	checksum	(6)
(1) Exclusive status			(2) ID number (Roland)			(3) Device ID (17)
(4) Model ID (XP-30)			(5) Command ID (RQ1)			(6) EOX

Next we calculate the checksum.

10H + 02H + 12H + 00H + 00H + 00H + 00H + 19H = 16 + 2 + 18 + 0 + 0 + 0 + 0 + 25 = 61 (sum)

61 (total) / 128 = 0 (product) ... 61 (remainder) checksum = 128 - 61 (remainder) = 67 = 43H

Thus, a message of F0 41 10 6A 11 10 02 12 00 00 00 00 19 43 F7 would be transmitted.

<Example 3> Retrieving data for Temporary Performance (RQ1)

*When a data transfer is executed in Utility mode, data that is accessed will be the same as that which is transmitted when the Type parameter is set to PERFORM and the Source parameter is set to TEMP: -PATCH

The “Parameter Address Map” gives the following start addresses for Temporary Performance data.

01 00 00 00H	Temporary Performance Common
01 00 10 00H	Temporary Performance Part 1
:
01 00 1F 00H	Temporary Performance Part 16

Since Performance Part has a size of 00 00 00 19H, we add that size to the start address of the Temporary Performance Part 16, resulting in:

01 00 1F 00H +) 00 00 00 19H 01 00 1F 19H

Thus, the Size for the retrieved data will be:

	01 00	1F	19H
-) 01 00 00			00H
	00 00	1F	19H
F0	41		10	6A	11	01 00 00 00	00 00 1F 19	??	F7
(1)	(2)		(3)	(4)	(5)	address	size	checksum	(6)
(1) Exclusive status				(2) ID number (Roland)			(3) Device ID (17)
(4) Model ID (XP-30)				(5) Command ID (RQ1)			(6) EOX

Calculating the checksum as shown in <Example 2>, we get a message of F0 41 10 6A 11 01 00 00 00 00 00 1F 19 47 F7 to be transmitted.

<Example 4> Retrieving the Temporary Performance data together with all Temporary

Part and Rhythm Set data (RQ1)

*When a data transfer is executed in Utility mode, the data that is accessed will be the same as that which is transmitted when the Type parameter is set to PERFORM and the Source parameter is set to TEMP: +PATCH

The “Parameter Address Map” gives the following start addresses for Temporary Performance, Performance Mode Temporary Patch and Performance Mode Temporary

Rhythm.
01	00 00 00H	Temporary Performance
02	00 00 00H	Performance Mode Temporary Patch(part 1)
	:
02	08 00 00H	Performance Mode Temporary Patch(part 9)
02	09 00 00H	Temporary Rhythm Setup
02	0A 00 00H	Performance Mode Temporary Patch(part 11)
	:
02	0F 00 00H	Performance Mode Temporary Patch(part 16)
The Patch offset addresses are as follows.
00	00H	Patch Common
10	00H	Patch Tone 1
:
16	00H	Patch Tone 4

Since Patch Tone has a size of 00 00 01 01H, we add this size to the start address of Performance Mode Temporary Patch (Part 16) Tone 4, to get:

02 0F 00 00H

1600H +) 00 00 01 01H 02 0F 17 01H

Thus, the size of the retrieved data will be:

02	0F	17	01H
-) 01	00	00	00H
01	0F	17	01H

F0	41	10	6A	11	01 00 00 00	01 0F 17 01	??	F7
(1)	(2)	(3)	(4)	(5)	address	size	checksum	(6)
(1) Exclusive status			(2) ID number (Roland)			(3) Device ID (17)
(4) Model ID (XP-30)			(5) Command ID (RQ1)			(6) EOX

Calculating the checksum as shown in <Example 2>, we get a message of F0 41 10 6A 11 01 00 00 00 01 0F 17 01 57 F7 to be transmitted.

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