Roland MT-32 Owner's Manual page 32

Roland
Exclusive
Messages
Data
Format for Exclusive
Messages
Roland's
MIDI implementation uses Ihe following data
format
for
al!
exclusive
messages (type IV)
:
Byte
Description
FOH
Exclusive status
41H Manufacturer
ID
(Roland)
OEV
Device
ID
MDL
Model
ID
CMD Command
ID
[BODY] Main data
F7H
End
of exclusive
#
MIDI status
FOH,
F7H
An
exclusive
message must be flanked by a
pair
of status
codes,
starting
with
o
Manufacturer- ID immediately after
FOH
(MIDI version!.
0).
#
Manufacturer-
ID
:
41H
The
Manufacturer- ID identifies the
manufacturer
of
a MIDI
inslrument that
triggeres
an exclusive message.
Value 41H
represents Roland's
Manufacturer -ID.
#
Device-
ID
:
DEV
The
Device- ID
contains a unique value that Identifies
the
individual
device in the multiple
implementation of
MIDI
instruments.
H
is
usually set to
00H
-
OFH, a
value
smaller
by one than that of a basic
channel, but value
OOH
-
1FH
may
be used for
a device with
multiple basic channels.
#
Model-
ID
:
MDL
The
Model
-ID
contains
a value that
uniquely
identifies
one
model from another. Different models,
however,
may share an
identical
Model-
ID
if
they handle similar data.
The Model -ID format
may
contain
00H
in
one or
more
places
to
provide
an extended data
field.
The
following are
examples
of valid
Model-IDs, each representing a
unique model
:
Q1H
02H
03H
0OH..O1H
00H,
02H
OOH, OOH,
01
#
Command-
ID
:
CMD
The Command -ID
indicates the
function of
an
exclusive
message.
The
Command
-ID formal
may
contain
OOH
in
one
or
more
places to
provide
an extended data
field.
The
following
are
examples
of valid
Command-IDs
,
each
representing, a
unique function
:
01H
0211
03H
OOH, 01
OOH,
02H
OOH, OOH, 01
#
Main
data
:
BODY
This
field
contains
a message
to
be exchanged across
an
interface.
The exact data
size
and contents
will
vary with the
Model-ID
and
Command-ID.
Address-
mapped
Data Transfer
Address
mapping
is
a
technique for transferring
messages
conforming
to
the data
format given
in
Section
1. It
assigns
a
series of
memory
-resident records
—
waveform and
tone
data,
switch status,
and parameters, for
example
—
to specific
locations in a
machine -dependent address
space, thereby
allowing access
to
data residing at the
address a
message
specifies.
Address
-mapped
data transfer
is
therefore
independent of
models and data categories.
This technique allows use
of
two
different
transfer
procedures
:
one— way
transfer
and
handshake
transfer.
#
One-
way
transfer
procedure (See Section3 for details.)
This procedure
is
suited for
Ihe transfer of
a small
amount
ol
data.
U
sends out an exclusive
message completely independent
of
a receiving device status.
Connection Diagram
Device (A)
Device (B)
MIDI
OUT
Mini
in
MIDf IN
MM
OUT
2
Connections! eoinl2
is
essentia! for
"Request data"
(See Sections.)
procedures.
#
Handshake-
transfer
procedure (See Section* for details.)
This procedure
initiates
a predetermined transfer
sequence
(handshaking) across the
interface
before data transfer
lakes
place.
Handshaking ensures that
reliability
and
transfer
speed
are
high
enough
to
handle a large
amount
of data.
Connection Diagram
Device (A)
Device (B)
Connections! points]
and 2
is
essential.
Notes on
the
above
two
procedures
* There
are separate
Command
-IDs
for
different transfer
procedures.
DevicosA and
D cannot exchange
data unless they use the
same
transfer
procedure, share identical
Device— ID and Model
ID,
and
are ready for
communication.
EM
One- way Transfer Procedure
This procedure sends out data
al!
the
way
until it
stops
when
the
messages are so short that
answerback* need
not
be
checked.
For long
messages, however,
the
receiving device
must acquire
each
message
in
time
with
the transfer
sequence,
which
inserts
intervals of
a! least
20miliiseconds
in
between.
Types
of
Messages
Message
Request data
1
Data set
I
Command
ID
RQ1
(MH)
DTI
(12H)
#
Request data
#1
RQ1 (11H)
This
message
is
sent out
when
there
is
a
need
to
acquire data
from
a device at
the other
end
of the interface. It
contains
data
(or
the address
and
site
that specify
designation
and
length,
respectively, of
da
la
required.
On
receiving
an RQI message,
the
remote
device
checks
its
memory
for
the data address and
size
that satisfy the request.
If it
finds
them and
is
ready
for
communication, the device will
transmit a
"Data set
1
(DTI)" message,
which contains
the
requested data.
Otherwise, the device will
send out nothing.
Byte
Description
FOH Exclusive status
41H
Manufacturer
ID
(Roland)
DEV
Device ID
MDL Model ID
1IH
Command
ID
aaH
Address
MSB
!
LS9
ssH Size
MSB
LSB
sum Check
sum
F7H
End
of exclusive