Roland Audio Canvas UA-100 User Manual page 89

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 ff gg hhH.
aa + bb + cc + dd + ee + ff + gg + hh = sum
sum / 128 = quotient... remainder
128 - remainder = checksum
<Example 1> Setting EFX TYPE for insertion effect 3 to Guitar Multi1
According to the Parameter Address Map, the address of the EFX TYPE for insertion
effect 3 is 00 40 03 30H, and the setting data for Guitar Multi1 is [04H, 00H]. Thus,
F0 41 10 00 11 12 00 40 03 00
(1) (2) (3) (4) (5) address
(1) Exclusive status, (2) ID (Roland),
(4) Model ID (UA-100), (5) Command ID (DT1),
Next we calculate the checksum.
00H + 40H + 03H + 00H + 04H + 00H = 0 + 64 + 3 + 0 + 4 + 0 = 71 (sum)
71 (sum) / 128 = 0 (quotient)... 71 (remainder)
checksum = 128 - 71 (remainder) = 57 = 39H
This means that F0 41 10 00 11 12 00 40 03 00 04 00 39 F7 is the message we transmit.
<Example 2> Requesting sending of UA-100 MODE (operating mode)
According to the Parameter Address Map, the address of the UA-100 MODE is 00 40
00 00H, and the size is 00 00 00 01H. Thus,
F0 41 0 00 11 11 00 40 00 00
(1) (2) (3) (4) (5) address
(1) Exclusive status, (2) ID (Roland),
(4) Model ID (UA-100), (5) Command ID (RQ1),
Next we calculate the checksum.
00H + 40H + 00H + 00H + 00H + 00H + 00H + 01H = 0 + 64 + 0 + 0 + 0 + 0 + 0 + 1 = 65 (sum)
65 (sum) / 128 = 0 (quotient) ... 65 (remainder)
checksum = 128 - 65 (remainder) = 63 = 3FH
This means that F0 41 10 00 11 11 00 40 00 00 00 00 00 01 3F F7 is the message we
transmit.
04 00 ?? F7
data checksum (6)
(3) Device ID (17),
(6) End of Exclusive
00 00 00 01 ?? F7
data checksum (6)
(3) Device ID (17),
(6) End of Exclusive
MIDI Implementation
89