Special Function Bytes - Kurzweil ExpressionMate User Manual

Sending MIDI Messages

Special Function Bytes

The MIDI special function ÒsystemÓ messages (those with a hex
value from $F0 to $FF) are brießy explained below. For more
detail refer to the MIDI spec.
SOX ($F0) and EOX ($F7) identify a System Exclusive message.
The number and format of the data bytes between the SOX and
EOX bytes is completely device dependent and varies with
manufacturer and model. Typically the Þrst data byte (or 3 bytes
for those who got into the game late) identiÞes the manufacturer.
Subsequent bytes identify the model and usually a device ID.
To Þnd out about the SysEx format for a speciÞc device, check the
ÒSysEx ImplementationÓ information in its manual.
MTC ($F1) is used to endow MIDI with a SMPTE-like absolute
time code capability. It is always followed by one 7-bit data byte
which is further broken down into bit Þelds. See the MIDI Time
Code spec for details. It is unlikely that MIDI time code would
ever need to be sent by the ExpressionMate
Song Position Pointer ($F2) is used to instruct a sequencer to fast-
forward (or rewind) to a speciÞc place in a performance. The two
data bytes identify the position. See the MIDI spec for details on
their format.
Song Select ($F3) is used to instruct a sequencer to Þnd and load a
speciÞc song. The single data byte identiÞes the song by number.
Tune Request ($F6) is used to instruct analog synthesizers to
retune or recalibrate themselves and is thus largely obsolete now.
Timing Clock (or simply just ÒclockÓ) is used to keep sequencers
and arpeggiators in sync. The MIDI standard calls for this byte to
be sent at 24 times the selected tempo. Thus for a 120BPM tempo,
the transmission rate would be 48 times per second. ItÕs unlikely
that sending single Clock messages using the MIDI strings
feature would be useful.
Start, Continue, and Stop are sequencer and arpeggiator controls
which perform the functions implied by their names.
Active Sensing ($FE) is used by some Japanese synthesizers to
signal ÒI'm aliveÓ to anything connected to their outputs. Its
intended use is to allow detection of an unconnected cable and
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