Roland RD-600 - Examples of Actual MIDI Messages; Calculating MIDI Checksums

@ Examples of actual MIDI messages
<Example 1> 92 3 SF
9n is the Note-on status, and nis 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 FH = 14 and
73, this is a Program Change message with MIDI CH = 15, program number 74
SA E.Grand 2 in RD-600).
<Example 3> EA 00 28
EnH is the Pitch Bend Change status, and n is the MIDI channel number. The 2nd byte
(OOH = 0) is the LSB and the 3rd byte (28H = 40) is the MSB, but Pitch Bend Value is a
signed number in which 40 OOH (= 64x 128 ~ 0 = 8192) is 0, so this Pitch Bend Value is
28 NOH - 40 GOH = 40x 128 + 0+ (64x 128 + 0) = 5120 - 8192 = -3072
If the Pitch Bend Sensitivity is set to 2 semitones, -8192 (00 OOH) will cause the pitch to
change -200 cents, so in this case -200 x (-3072) / (-8192) = -75 vents of Pitch Bend is being
applied to MIDI channel 11.
<Example 4> 83 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. fn a case in
which two or more messages consecutive messages have the same status, MIDI has a pro-
vision 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
BI 64.00 MIDI cha, lower byte of RPN parameter number: 00H
(B3) 65.00 (MIDI ch.4) upper byte of RPN parameter number: OOH
(B3) 060C (MIDI ch) upper byte of parameter value: OCH
(B3) 2600) (MIDI ch.4) lower byte of paraineter value: OH
(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
In other wards, the above messages specify a value of OC OOH for RPN parameter number
00 OOH 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 indi-
cates semitone units, so a value of OCH = 12 sets the maximum pitch bend range to +12
semitones (1 octave). (On RD-600 sound sources the LSB of Pitch Bend Sensitivity 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 KPN or NRPN, all Data Entry mes-
sages transmitted on that same channel will be valid, so atter the desired value has been
transmitted, it is a good idea to sct the parameter number to 7F 7FH to prevent accidents.
This is the reason for the (B3) 64 7F (B3) 65 7F at the end.
ft 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 source 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 setting
be done in the proper order. On sume sequencers, events occurring in the same (or consec-
utive) clock may be transmitted in an order different than the order in which they were
received. Por this reason il is a good idea to slightly skew the time of each event (about 1
tick lar TPQN = 96, and about § ticks for FPQN = 481).
* FPON: Ticks Per Quarter Note
72
@Exampie of an Exciusive message and calculating a
Checksum
Roland Exclusive messages (ROV, DTI} are transmitted with a checksum at the end
(before F7} ta make sure that the messape was correctly received. The value of the check-
sum 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 thal in the exclu-
sive message we are transmitting, the address is aa bb cc ddl and the data or size is ee ff
yg hhH.
aat bb coe dd + ee 4 ff + ge + hh =sum
sum / 128 = quotient ... remainder
128 - remainder = checksum
<Example 1> Setting “Effect Reverb type” of “Tempotary” to “ROOM1" (DT1).
The “Parameter address map” indicates that the starting address of the Temporary is 4
00 00 OOH, that the Effect Parameter offset address is 30 00H, and that the “Reverb type”
type address is OOH. Thus, the address is:
Since “ROOM1” is parameter value 00H,
FO 4) 10 0009 12 01003000 OG 2? F7
a) 2) @ (4) (5) address data checksum (6)
(1) Exclusive status (2) {1D number (Roland) — (3) device ID(17)
(4) model [D (RD-600) {5) command [ID (DT1} {b) EOX
Next we calculate the checksum.
OH + OOH + 301] + OOH + OOH = 1+ 04 48-0 + 0 = 49(sum)
49 (total) + 128 = 0 (quotient)... 49 (remainder)
checksum = 128 - 49 (quotient) = 79 = 4FH
This means that the message transmilted will be FO 41 10.00.09 £2.01 00-30 0000 4F F7.
<Example 2> Retrieving data for Temporary Rx.Part2 Parameter (RQ1)
The “Parameter address map” indicates that the starting address of Temporary is 01 00.00
OOLL and that the offset address of Rx.Part2 Parameter is 20 01H.
Thus, the address is:
Since the size of the Performance Part is 00.00 00 09H,
FO 4h 1 00098 iT Ob 0e2001 0800 0009 2? F7
{t) (2) @) (4) (3) address size checksum (6)
(EL) Exclusive status (2) 1D number (Roland) (3) Device 117)
(4) Model [D (RD-600) (5) Command ID (RQ) (6) EOX
Next we calculate the checksum.
OTH = 00H + 20H + 01H + 00H + O01 + QOH + 09H =
1+0+324140-0+ 0+ 9=43(sum)
43(total) + 128 = Oproduct) ... 43(remainder}
checksum = 128 - 43{remainder) = 85 = 55H
Thus, a message of Fo 41 £0 04.09 11701 00 20.41 00-00.00 09 55 F7 would be transmitted.