05-System+Messages


 * System Messages**

Within the MIDI language there is a subset of protocols that are understood by all MIDI compatible devices. These protocols are named "Universal System Exclusive Messages" though are often referred to as SysEx messages. The messages are composed of two parts. Part A, tells the computer that the message is in fact a Universal System Exclusive Message. Part B, tells the computer which one it is.

Breakdown of SysEx Messages:

The first of these messages is the System Exclusive (Data Dump). It is used to reset the midi device in order to allow data writing by another message.

The second is the "Time Code Quarter Frame" this is used for synchronizing midi devices

Song position pointer is the third message. This is a register that records the number of MIDI beats since the beginning of the song allowing the user to playback from any point

Song select (Song no) simply selects audio files for playback

Tune Request Tunes the oscillators of the synthesizers, making sure that they are all as close to perfect pitch as possible

The sixth message (EOX) End of SysEx is used to flag the end of a system message

The Seventh and Eight messages are empty carrying no data

Timing clock is the eight message, it is used to synchronize the internal midi clock.

Start is the ninth message simply beginning the playback sequence

Continue resume current playback from where stopped

Stop will stop the current sequence playback in place

Thirteen is the Active Sensing message. Active sensing works to ensure against stuck notes due to disconnected cables. When a cable disconnects before the stop message is received, the note will continue to play. With Active Sensing engaged this problem is averted.

Reset This is used to reset all of the devices in the system and should be initiated manually.

The fifteenth and sixteenth messages are again undefined and devoid of content.