For data where greater precision is required, we must use two or more bytes. For example, two hexadecimal 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, OH = -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 OOH = -8192,40 OOH = ±0, and 7F 7FH = +8191. For example if aa bbH were expressed as decimal, this would be aa bbH - 40 OOH = aax 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 ObH has the value of a x 16+b. 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, DTI) 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 r EM-50/30/20/10 MIDI Implementation 29 ❖ 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 ccH and the data or size is dd ee ffH. aa+bb+cc+dd+ee+ff = sum sum ] 128 = quotient... remainder 128 - remainder = checksum Setting REVERB MACRO to ROOM 3 According to the 'Parameter Address Map/ the REVERB MACRO Address is 40 01 30H, and ROOM 3 is a value of 02H. Thus, EG 41 in 42 12 4O0L3Q Q2 22 EZ (1) (2) (3) (4) (5) address data checksum (6) (1) Exclusive Status, (2) ID (Roland), (3) Device ID (17), (4) Model ID (GS), (5) Command ID (DTI), (6) End of Exclusive Next we calculate the checksum. 40H+01H+30H+02H = 64+1+48+2 = 115 (sum) 115 (sum)) 128 = 0 (quotient)... 115 (remainder) checksum = 128 -115 (remainder) = 13 = ODH This means that FO 41 10 42 12 40 01 30 02 0D F7 is the message we transmit. Requesting transmission of the LEVEL for DRUM MAP 1 NOTE NUMBER 75 (D#5; Claves) NOTE NUMBER 75 (D#5) is 4BH in hexadecimal. According to the “Parameter Address Map/ LEVEL of NOTE NUMBER 75 (D#5; Claves) in DRUM MAP 1 has an Address of 41 02 4BH and a Size of 00 00 01H. Thus, EQ 41 JQ 42 11 41MM mmi 22 £2 (1) (2) (3) (4) (5) address size checksum (6) (1) Exclusive Status, (2) ID (Roland), (3) Device ID (17), (4) Model ID (GS), (5) Command ID(RQ 1), (6) End of Exclusive Next we calculate the checksum. 41H+02H+4BH+00H+00H+01H = 65+2+75+0+0+1 = 143 (sum) 143 (sum)} 128 = 1 (quotient)... 15 (remainder) checksum = 128-15 (remainder) =113 = 71H This means that F0 41 10 42 11 41 02 4B (X) 00 01 71 F7 is the message we transmit. • About tuning In MIDI, individual Parts are tuned by sending RPN #1 (Master Fine Tuning) to the appropriate MIDI channel. In MIDI, an entire device is tuned by either sending RPN #1 to all MIDI channels being used, or by sending a System Exclusive MASTER TUNE (address 40 CO 00H). RPN #1 allows tuning to be specified in steps of approximately 0.012 cents (to be precise, 100/8192 cent), and System Exclusive MASTER TUNE allows tuning in steps of 0.1 cent. One cent is 1/100th of a semitone. The values of RPN #1 (Master Fine Tuning) and System Exclusive MASTER TUNE are added together to determine the actual pitch sounded by each Part. Frequently used tuning values are given in the following table for your reference. Values are in hexadecimal (decimal in parentheses). [Hz at A4 I cent 1 RPN #1 I Sys.Ex. 40 00 00 445, .0 I +19 .56 1 1 4C 43 ( >1603) 1 00 04 ОС 04 (+196) 444. .0 1 +15 .67 1 1 4A 03 ( >1283)1 00 04 09 0D (+157) 443, .0 1 +11 .76 1 1 47 44 ( > 964)1 00 04 07 06 (+118) 442. .0 1 + 7 .85 1 1 45 03 ( > 643)1 00 04 04 OF (+ 79) 441, .0 1 + 3 .93 1 1 42 42 < > 322) 1 00 04 02 07 (+ 39) 440. • o 1 0 1 1 40 00 ( : 0 ) I 00 04 00 00 ( 0) 439, .0 1 - 3 .94 1 1 3D 3D < > 323) 1 00 03 0D 09 (- 39) 438. .0 1 - 7 .89 1 1 ЗА 7A ( > 646) 1 00 03 0B 01 (- 79) Set the tuning of MIDI channel 3 to A4 = 442.0 Hz Send RPN#1 to MIDI channel 3. From the above table, the value is 45 03H. B2 6400 MIDI ch.3, lower byte of RPN parameter number : ООН (B2) 6501 (MIDI ch.3) upper byte of RPN parameter number : 01H (B2) 0645 (MIDI ch.3) upper byte of parameter value : 45H (B2) 2603 (MIDI ch.3) lower byte of parameter value : 03H (B2) 64 7F (MIDI ch.3) tower byte of RPN parameter number : 7FH (B2) 65 7F (MIDI ch.3) upper byte of RPN pa...
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