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APPENDIX A
DATA FORMAT
The messages used to control the system exclusives accept data in the following formats:
format =0 (7 bit data value): the natural data format with values from 0 to 127. Does not require any form of treatment.
format =1 (7 bit wide word LSB_J): the value of the data present in the stream has a range defined by the number of bytes
transmitted. For example, to transmit the hexadecimal value F123 (61731 decimal) three bytes configured as follows are re-
quired:
03 62 23. This format is useful to transmit single data (byte, short, int, long, float, double) which do not fall within the range 0-127.
format =2 (nibble): single byyes contain only 4 significant bits but which can represent much greater values. for example, to
transmit the hexadecimal value F123 (61731 decimal) would require four bytes configured as: 0F 01 02 03; i practice, each single
byte is sliced in two and transmitted on two bytes with the four most significant bits at 0.
format =3 (octect): the bytes are groups in sets of 8 Bytes with 7 significant bits to represent 7 real bytes in 8 MIDI bytes (56 bit).
This format allows, therefore, to achieve maximum compactness of the data to transmit in cases of data consisting of a large
number of bytes whose priory value is not known.
The procedure is as follows: from each bytes of the 7 in sequence, the least significan bit is extracted and saved in an eighth byte,
therefore the same byte is shifted to the right; finally all is transmitted in the order. For example:
7 real bytes = 0x11 0x22 0x33 0x44 0x55 0x66 0x77
then shifting to the right and memorizing in a byte the "extracted" bits:
0x11 = 0x09 + 1 (b0)
0x22 = 0x11 + 0 (b1)
0x33 = 0x1A + 1 (b2)
0x44 = 0x22 + 0 (b3)
0x55 = 0x2B + 1 (b4)
0x66 = 0x33 + 0 (b5)
0x77 = 0x3C + 1 (b6)
8 byte Midi = 0x09 0x11 0x1A 0x22 0x2B 0x33 0x3C 0x55.
format =4 (nibble data dump): the single bytes containing only 4 significant bits to be able to represent any data stream. For
example, the stream "ciao" corresponds to the ASCII data 0x63 0x69 0x61 0x6f and will, therefore, be represented by the follow-
ing bytes: 0x06 0x03 0x06 0x09 0x06 0x01 0x06 0x0f.
format =5 (BCD data dump): the single bytes are subdivided in two nibbles and subsequently converted in BCD; this is a format
particularly useful with numerical data which does not permit direct visualization. For example, the number 0x12345678 corre-
sponds to the ASCII data 0x12 0x34 0x56 0x78 which subdevided in nibbles give:
which when conve rted in BCD give:
0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38
which when shown on the terminal gives the stream "12345678", representing the initial data.
8 byte: 0x01
0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08
0x01
0x05
0x05
0x15
0x15
0x55
System Exclusive A•41
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