E-Mu Vintage Keys Operation Manual page 123

MIDI SPECIFICATIONS
• 14-bit Signed 2's Complement Numbers
If the data value is negative, you must first take the 2's complement of
the number: In the case of a 14-bit number this is equivalent to add-
ing 16384 to the original negative value.
To fit the 7-bit MIDI protocol, numbers must be "nibble-ized".
Status Bit MUST be "0"
in MIDI data bytes.
To get the 14-bit nibble-ized value (of a positive value or a 2's
complemented negative value):
msb = value DIV 128 (divide and ignore the remainder)
lsb = value MOD 128 (divide and use only the remainder)
To go the other way (convert 14 bit signed 2's complement to a signed
real number)
raw Value = (msb*128) + lsb (gives you the unsigned raw value)
if raw Value ≥ 8192
then signed Value = raw value - 16384
Example: To find the "nibble-ized" Hex value of -127:
1) -127 + 16384 = 16252
16252 ÷ 128 = 126 r-124
2)
3) 126 in Hex = 7E = msb
4) 124 in Hex = 7C = lsb
5) Parameter value would be transmitted as 7C 7E
Example: To find the "nibble-ized" Hex value of parameter number
257:
257 ÷ 128 = 2 r-1
1)
2) 2 in Hex = 02 = msb
3) 1 in Hex = 01 = lsb
4) Parameter number would be transmitted as 01 02
114 Vintage Keys Operation Manual
data bits data bits
00000000 00000000
Status Status
Bit Bit
(8192 = 2^13)
(16384 = 2^14)