Roland SC-88 Pro manual 209

Section 5. Supplementary material

●Decimal and Hexadecimal table

(An 'H' is appended to the end of numbers in hexadecimal notation.)

In MIDI documentation, data values and addresses/sizes of exclusive messages etc. are expressed as hexadecimal values for each 7 bits.

The following table shows how these correspond to decimal numbers.

+	-------	+	-------	++	-------	+	-------	++	-------	+	-------	++	-------	+	-------	+
	Dec.		Hex.		Dec.		Hex.		Dec.		Hex.		Dec.		Hex.
+	-------	+	-------	++	-------	+	-------	++	-------	+	-------	++	-------	+	-------	+
	0		00H		32		20H		64		40H		96		60H
	1		01H		33		21H		65		41H		97		61H
	2		02H		34		22H		66		42H		98		62H
	3		03H		35		23H		67		43H		99		63H
	4		04H		36		24H		68		44H		100		64H
	5		05H		37		25H		69		45H		101		65H
	6		06H		38		26H		70		46H		102		66H
	7		07H		39		27H		71		47H		103		67H
	8		08H		40		28H		72		48H		104		68H
	9		09H		41		29H		73		49H		105		69H
	10		0AH		42		2AH		74		4AH		106		6AH
	11		0BH		43		2BH		75		4BH		107		6BH
	12		0CH		44		2CH		76		4CH		108		6CH
	13		0DH		45		2DH		77		4DH		109		6DH
	14		0EH		46		2EH		78		4EH		110		6EH
	15		0FH		47		2FH		79		4FH		111		6FH
	16		10H		48		30H		80		50H		112		70H
	17		11H		49		31H		81		51H		113		71H
	18		12H		50		32H		82		52H		114		72H
	19		13H		51		33H		83		53H		115		73H
	20		14H		52		34H		84		54H		116		74H
	21		15H		53		35H		85		55H		117		75H
	22		16H		54		36H		86		56H		118		76H
	23		17H		55		37H		87		57H		119		77H
	24		18H		56		38H		88		58H		120		78H
	25		19H		57		39H		89		59H		121		79H
	26		1AH		58		3AH		90		5AH		122		7AH
	27		1BH		59		3BH		91		5BH		123		7BH
	28		1CH		60		3CH		92		5CH		124		7CH
	29		1DH		61		3DH		93		5DH		125		7DH
	30		1EH		62		3EH		94		5EH		126		7EH
	31		1FH		63		3FH		95		5FH		127		7FH
+	-------	+	-------	++	-------	+	-------	++	-------	+	-------	++	-------	+	-------	+

*Decimal values such as MIDI channel, bank select, and program change are listed as one greater than the values given in the above table.

*A 7-bit byte can express data in the range of 128 steps. For data where greater precision is required, we must use two or more bytes. For example, two hexadeci- mal numbers aa bbH expressing two 7-bit bytes would indicate a value of aa x 128+bb.

*In the case of values which have a ± sign, 00H = -64, 40H = ± 0, and 7FH = +63,

so that the decimal expression would be 64 less than the value given in the above chart. In the case of two types, 00 00H = -8192, 40 00H = ± 0, and 7F 7FH = +8191. For example if aa bbH were expressed as decimal, this would be aa bbH - 40 00H = aa x 128+bb - 64 x 128.

*Data marked "Use nibbled data" is expressed in hexadecimal in 4-bit units. A value expressed as a 2-byte nibble 0a 0bH has the value of a x 16+b.

<Example 1> What is the decimal expression of 5AH ? From the preceding table, 5AH = 90

<Example 2> What is the decimal expression of the value 12 34H given as hexadecimal for each 7 bits?

From the preceding table, since 12H = 18 and 34H = 52 18 x 128+52 = 2356

<Example 3> What is the decimal expression of the nibbled value 0A 03 09 0D ? From the preceding table, since 0AH = 10, 03H = 3, 09H = 9, 0DH = 13

((10 x 16+3) x 16+9) x 16+13 = 41885

<Example 4> What is the nibbled expression of the decimal value 1258?

16) 1258

16) 78 ... 10

16) 4 ... 14

0 ... 4

Since from the preceding table, 0 = 00H, 4 = 04H, 14 = 0EH, 10 = 0AH, the answer is 00 04 0E 0AH.

●Examples of actual MIDI messages <Example 1> 92 3E 5F

9n is the Note-on status, and n is 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 EH = 14 and 49H = 73, this is a Program Change message with MIDI CH = 15, program number 74 (Flute in GS).

<Example 3> EA 00 28

EnH is the Pitch Bend Change status, and n is the MIDI channel number. The 2nd byte (00H = 0) is the LSB and the 3rd byte (28H = 40) is the MSB, but Pitch Bend Value is a signed number in which 40 00H (= 64 x 12+80 = 8192) is 0, so this Pitch Bend Value is

28 00H - 40 00H = 40 x 12+80 - (64 x 12+80) = 5120 - 8192 = -3072

If the Pitch Bend Sensitivity is set to 2 semitones, -8192 (00 00H) will cause the pitch to change -200 cents, so in this case -200 x (-3072) ⎟ (-8192) = -75 cents of Pitch Bend is being applied to MIDI channel 11.

<Example 4> B3 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. In a case in which two or more messages consecutive messages have the same status, MIDI has a provision 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.

B3	64	00	MIDI ch.4, lower byte of RPN parameter number	: 00H
(B3)	65	00	(MIDI ch.4) upper byte of RPN parameter number	: 00H
(B3)	06	0C	(MIDI ch.4) upper byte of parameter value	: 0CH
(B3)	26	00	(MIDI ch.4) lower byte of parameter value	: 00H
(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 words, the above messages specify a value of 0C 00H for RPN parameter number 00 00H 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 indicates semitone units, so a value of 0CH = 12 sets the maximum pitch bend range to ± 12 semitones (1 octave). (On GS 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 RPN or NRPN, all Data Entry messages transmitted on that same channel will be valid, so after the desired value has been transmitted, it is a good idea to set the parameter number to 7F 7FH to prevent accidents. This is the reason for the (B3) 64 7F (B3) 65 7F at the end.

It 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 some sequencers, events occurring in the same (or consecutive) clock may be transmitted in an order different than the order in which they were received. For this reason it is a good idea to slightly skew the time of each event (about 1 tick for TPQN = 96, and about 5 ticks for TPQN = 480).

* TPQN: Ticks Per Quarter Note

●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.

Chapter 8. Appendix 207