Roland MT-32 - 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
H
#
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
H
OOH, 02H
OOH, OOH,
01
H
#
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 dala
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