Roland SK-50 Owner's Manual page 20

System Real Time Messages
System Real Time Messages are used to achieve synchronization among MIDI devices.
Start
<TX> When the NUMBER 5 button is pressed while the MIDI button is held down, a "Start"
message (System Real Time) will be transmitted (
sequencer.
Stop
<TX> When the NUMBER 6 button is pressed while the MIDI button is held down, a "Stop"
message (System Real Time) will be transmitted (
stop an external sequencer.
Active Sensing
These messages are designed to detect abnormalities (such as MIDI cables accidentally being
disconnected, or damaged cable elements) which could cause notes to go on sounding
meaninglessly, or other problems.
<TX> Active Sensing messages are sent out approximately every 250 ms.
<RX> Once even one Active Sensing message has been received, the unit will thereafter
consider the arrival of Active Sensing messages at regular intervals to be the normal state of
operation. If an interval greater than about 420 milliseconds passes without a MIDI message
being received, the unit will assume that an abnormality has occurred, and will stop sounding
all notes.
System Exclusive Messages
Exclusive messages are used to control features that are unique to a certain manufacturer or
device. For this reason, all devices on line need to be able to know whether or not each
Exclusive message is directed at them, or is meant for one of the other devices. For this purpose,
these messages need to carry a Manufacturer's ID, Device ID, or a Model ID. Note, however,
that messages such as "GM System ON," which are designed to be used broadly, without being
limited to a particular manufacturer or model, fall into a different category known as "Universal
Exclusive" messages.
Since the SK-50's sound generator complies with the GS Format, it can transmit/receive
Exclusive messages that are common to all GS Format sound generators (Model ID: 42H).
GM System ON (Universal Exclusive)
The GM System ON message is used to set the values for all settings in any GM sound generator
to the GM basic setteings.
<RX> The instrument will be set to the basic settings for GM System devices. Thereafter, it
ignores all NRPNs.
p. 25). This can be used to start an external
p. 25). This can be sent when you wish to
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