Command_formats
Command_formats fall into the categories of General, Specific and All-types. General command_formats have a least significant nibble equal to 0, except for lighting which is 01H. Specific command_formats are related to the General command_format with the most significanl nibble of the same value, but represent a more restricted range of functions within the format.
Command_format "All-types" (7FH) is used for system wide "broadcasts" of identical commands to devices of the same device_lD (or to all devices when used with <device_lD>=All-call>; see Device Identification, above). For example, use of the All-types command_format along with the All-call device_lD allows a complete system to be RESET with a single message.
Controlled Devices will normally respond to only one command_format besides All-types. Occasionally, more complex control systems will respond to more than one command_format since they will be in control of more than one technical performance element. Controllers, of course, should normally be able to create and send commands in all command_formats, otherwise their usefulness will be limited.
Table XXII
AIthough it can be seen that a wide variety of potentially dangerous and life-threatening performance processes may be under MIDI Show Control, the intent of this specification is to allow the user considerably more exacting and precise control over the type of command_format and command which will result in the desired result than normally may be provided in a non-electronic cueing situation. The major advantages to the use of MIDI Show control in these conditions are:
In no way is this specification intended to replace any aspect of normal performance safety which is either required or makes good sense when dangerous equipment is in use. Manual controls such as emergency stops, deadman switches, confirmation enable controls or like safety devices shall be used for maximum safety.
Automatic safety devices such as limit switches, proximity sensors, gas detectors, infrared cameras and pressure and motion detectors shall be used for maximum safety. MIDI Show Control is not intended to tell dangerous equipment when it is safe to go: it is only intended to signal what is desired if all conditions are acceptable and ideal for safe performance. Only properly designed safety systems and trained safety personnel can establish if conditions are acceptable and ideal at any time.
Recommended Minimum Sets
MIDI Show Control does not specify an absolute minimum set of commands and data which must be implemented in each device responding to a given command_format.
However, in order to ease the burden of interfacing between Controllers and Controlled Devices from different manufacturers, four RECOMMENDED MINIMUM SETS of commands and data have been created. Once a Controlled Device is specified to conform to a particular Recommended Minimum Set, then the task of designing a Controller which will successfully operate that device is considerably simplified.
The currently defined Recommended Minimum Sets are:
General Commands The following commands are basic to the current implementation of Memory Lighting systems and probably apply to all dedicated theatrical show control systems in a general sense. Although it is not required that Controlled Devices incorporate all of these commands, it is highly recommended:
Table XXIII
Sound Commands The following commands, in addition to the above, are basic to the current implementation of Computer Controlled Sound Memory Programming Systems and are widely used by Show Control Systems in more comprehensive applications. It is recommended that Controllers support the transmission of these commands:
Table XXIV
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