Theatre Design & Technology - Summer 1992 - 56

In rhe following documenrarion, as
well as in MIDI specifIcarions generally,
rransmirred dara is expressed in irs hex
form, often including an "H" immediareIy afrer each byre ro confirm irs hex
narure. (For a full explanarion of hex
norarion specifically relaring ro MIDI
implemenrarion, please refer ro rhe
MIDI 1.0 specifIcarion, since rhe subjecr
is well rreared and beyond rhe scope of
rhis arricle.) MSC is complerely conrained wirhin rhe Universal Real Time
Sysrem Exclusive message formar. All
messages of rhis rype begin wirh FOH (=
stare. of SysEx) followed by 7FH
(= Universal Real Time header)
rhen a user defined desrinarion address in
rhe range 00H-7FH ( = device_IO
0.) and 02H ( = MSC message
header) -all in fronr of rhe command
variables and relared dara in rhe message.
The message is rerminared by F7H ( =
end of SysEx) and rhe maximum
lengrh of any MSC message is 128 byres.
Wirhin rhese paramerers, a number
of variables may be senr as follows (in
hex):

FO 7F  02
   F7
Command formae. rells rhe addressed
device whar kind of message is being
senr, including general caregories of
lighring, sound, machinery, video, projecrion, process conrrol, pyro, and allrypes. A number of sub-caregories are
defined (excepr under all-rypes) and
rhere is room for furure expansion along
wirh rhe abiliry ro address an enrire
group or jusr a specific sub-caregory (see
Table 1).
The command rells rhe Conrrolled
Device wirh a marching device_IO
and command_format whar rhe Conrroller wishes ir ro do. Commands may
be simple or complex, wirh rhe Conrrolled Device's response designed ro be
appropriare for rhe applicarion. A number of dara variables may follow each
command so rhar rhe mosr complex
devices can be conrrolled while simpler
Conrrolled Devices simply ignore rhe
informarion rhey do nor use. Variables
are senr in rhe order of generic ro specific, wirh null characrers (OOH) separaring each one. Each Conrrolled Device
may use rhe dara variables of each command in irs own way, bur 1024 Srandard
Generic Conrrol Numbers have been
defined for lighring-wirh 14,000 more
undefined.
The fIrsr group of commands defined
are: GO (OlH); STOP (02H);
54

1992 SUMMER

TD&T

TABLE 1

00

reserved for extensions

01
02
03
04
05
06

=-.igne.:. g (Genera:'Cae.egory)
Moving Lighe.s
Colour Changers
Strobes
=-.asers
Chasers

10
11
12
13
14
15
16
17
18

Sound (General Category)
Music
CD Players
EPRO 1 Playback
Audio Tape Machines
Intercoms
Amplifiers
Audio Effects Devices
Equalizers

20

Machinery (General Category)
Rigging
Flys
Life.s
Turn abies
russes
Robots
.::>nimation
Floa s
reakaltlays
Barges

21
22
23
24
25
26
27
28
29
2A
30
3
32
33
34
35
36
37
38

40
41
42
43
4
45
50
51
52
53
54
55
56
57
5

ideo
Video
Video
Video
'!ideo
Video
Video
tors
Video
Video

(General Category)
ape Machines
Cassee. e Machines
Disc Players
SItlitchers
Effec s
Character GeneraStill Stores
Monitors

Projection (General Category)
Film Projectors
Slide Projectors
Video Projectors
oissolvers
Shutter Controls
Process Control (General
Ca egory)
Hydra lic Oil
H'O
CO'
Compressed Air
a ural Gas
Fog-

Smoke
Cracked Haze

60
61
62
63
64

Pyro (Ge eral Ca egory)
Fireworks
Explosions
Flame
Smoke po s

7F

All-types

RESUME (03H); TIMED_GO (04H),
which is like GO wirh an execurion rime;
LOAD (05H), which purs a cue inro
srandby, ready ro execure immediarely;
and GO_OFF (OBH), which srans a rransi rion or fade ro an off srare. Each can
oprionally conrain a cue number, a cue
lisr, and a cue parh as dara. SL' (06H)
defines rhe value of a numbered Generic
Conrrol and may include an execurion
rime; FIRE (07H) rriggers a numbered
macro; .~L_OFF (08H) rurns everyrhing off; RES ORE (09H) resrores
everyrhing as ir was prior ro .~L_OFF;
RESET (OAH) presers ro rhe rop of rhe
show.
The second group of commands are
specific ro com purer conrrolled rhearrical
sound sysrems: GO/JAM_CLOCK (10H),
which forces rhe auro follow clock rimer
ro rhe rime of rhe auro follow cue;
STANDBY_+ (llH) and STA.NDBY_(12H), which load inro srandby rhe nexr
or
previous
cue,
respecrively;
SEQUENCE_+ (l3H) and SEQUENCE_(14H), which load inro srandby rhe nexr
or previous parenr (using the whole inreger value of the cue only) cue;
STAR _CLOCK (l5H) , STOP_CLOCK
(16H),
ZERO CLOCK
(17H),
SET_CLOCK (18H), which srarr, srop,
reser and ser rhe clock rimer ro a parricuC_CH.:"'SE_O
(19H) and
lar rime;
M C_CHASE_OFF (lA.H) , which lock
and unlock rhe clock rimer ro incoming
MIDI Time Code; OPE _CUE_LIS
(lBH) and CLOSE_CUE_LIST
(lCH) , which include in rhe show or
exclude from rhe show a specified Cue
Lisr and rhe cues ir conrains; and
OPEN_CUE_PATH (lDH) and CLOSE
_CUE_PATH (1 EH) , which include in
rhe show or exclude from rhe show a
specified Cue Parh.
A srandard command dara formar for
cue, cue lisr and cue parh numbers is parr
of rhe specifIcarion.
umbers including
decimal poinrs are rransmirred as ASCII
characrers (0-9 = 30H-39H; u . u =
2EH). For many commands, cue numbers are oprional, as are Cue Lisr and Cue
Parh dara, and rhe Conrrolled Device
may simply discard dara rhar it does nor
supporr. In rhis way, rhe srandard provides a rremendous amounr of flexibility
for complex sysrems while allowing rhe
same commands ro be used wirh much
simpler devices. Time dara is represenred
in rhe srandard full form MIDI Time
Code (MTC) formar, which is basically
an expanded implemenrarion of SMPTE
Time Code wirh accuracy ro 11100 ofa
frame (330 microseconds).
As an example, here's how an MSC
message would acrually look (in hex):
Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1992
