Trigger command – Grass Valley Switcher Products User Manual
Page 101
Switcher Products — Protocols Manual
101
Commands
Trigger Command
The controlling device sends a Trigger command to a selected controlled
device to cause the controlled device to lunch or run an event which has
previously been readied. An example of this is an interface to a character
generator where a disk read, whose execution time is unpredictable, recalls
the text of a credit roll sequence. This event is then followed by a precisely
timed Trigger command which causes the credit roll to begin.
The Trigger command would be sent either as part of a register recall, when
a trigger keyframe is encountered on an effect timeline, or as the result of
some manual operation on the panel. When invoked as part of a Recall
command, the Trigger command is sent to the selected controlled device
prior to the vertical interval in which the controlling device will actually
perform the Recall.
No response to the message is required of the controlled device other than
to launch the desired event.
The format for a Trigger command is:
Tddddddg
•
The first byte is the ASCII keyword for Trigger, T (54H).
•
Next a six-byte field of ASCII characters (dddddd) acts as a bit map that
identifies which controlled devices are included in the Trigger (see
).
•
Next the controlling device sends the ASCII character (g) representing
a hex number that corresponds to the controlled device function which
the controlling device wants the controlled device to launch (0H-FH).
•
A carriage return ends the message.