#
Data
set
1
*The
size
of
the
requested
data
does
not
indicate the
number
of bytes
that
will malte
UP
a DTI message, but
represents
the address fields
where
the requested data resides.
*Some
models
1m!
subject to Umllations in
data
fonnat
used
for a single transaction. Requested data,
for
example, may
have a
limit in length
or
must be dIvided into predetermined
address
fields before
It
is exchanged across the interlace.
*The
same
number
of bytes comprises address and size data,
which, however, vary with the Model - lD.
*The
error
checking process uses a checksum that provides
a bit
pattern
where
the least signifil::anl 7 bits are zero
when
values
for
an
address,
size,
and
that
checksum are summed.
DTI (12H)
This message corresponds to the actual data
transfer
process.
Because
every
byte
in
the
data
Is
assigned a unique address,
a DTI message
!:.an
conveY
the
starting address
of
one
or
more data
as
well as a series
of
data
formaUed
in
an
address
-
dependent
order.
The
MIDI
standards
inhibit non - real time messages from
interrupting
an
exclusive one.
This
fact is inconvenient for the
devices that support a
~soft
- through
M
mechanism.
To
maintain compatibility with such devices. Roland has limited
the
DTl
to
256 bytes so
that
an
excessively long message is
sent
out in
separate
segments.
Byte
Description
FOH
Exclusive
41H
Manufacturer
ID
(Roland)
DEV
Device
ID
MDL
Mode:
ID
12H
Commano ID
"H
Address
MSB
'loSB
doH
Data
.em
Check
.om
F7H
End
of
exclusive
* A
OTl
message is capable of providing only
the
valid data
among
those specified by
an
RQJ message.
* Some models
are
subject
to
nmitation~
in data fonnat used
for a single transaction.
Reque~ted
data, for example, may
have a limit in length
or
mu~l
be divided into predetermined
address fields before it
is exchanged across
the
interface.
* The
number
of
bytes comprising address
data
varies from
one
ModeJ
- lD to another.
* The
error
checking
process uses a checksum that provides
a
bit
pattern
where
the least
~ignifjcan\
7 bits
are
zero when
values for
an
address, size, and that
check~um
are
summed.
:;::
Example
of
Message
Transactions
22
• Device A sending data to
DeVice
B
Transfer of a
OTl
message is
aU
that takes place.
I Device
(A)
I
[Data
set
1)
•
IDevice
(B)'I
*
More
than
20m
sec
time
internal.
(Dllte
set
1)
•
[Data
sat
1 J
..
• Device B
requesting
data
from Device A
Device B
sends
an
RQl
message
to Device
A.
Checking the
message, Device A
sends
a
OT!
message back to Device
B.
! Device
(Al
I
I
Device
(B)
I
[Data
. "
I)
•
[Request
datil]
[Datil
..
t
1)
•
*
More
than
20m
."
time
internal.
(Datil
set
1)
•
(Data
set
1J
•
II!
Handshake
-
Transfer
Procedure
\
Handshaking is an interactive process
where
two devices
exchange
eITOf
checking signals before a message transaction
takes
place, thereby increasing
data
reliability. Unlike
one-
way,
transfer
that
in5!!rts a pause between message transactions,
handshake
transfer allows much speedier transactions because
data transfer starts once the receiving device
returns
a ready
signal.
When it comes to handling large amounts of
data
- - sampler
waveforms and
synthesizer tones
over
the entire range, for
example - -
across a MID! interface, handshaking
transfer
is
more efflCient than one - way transfer.
Types
of
Messages
MesseiOle
Command ID
Want
:0
send
data
WSD
(40H)
Request
data
RGO
(41H)
Datil
set
OAT
(42H)
Acknowledge
ACK
(43H)
End
of
date
EOD
(45H)
Communicatio"
error
:;RR
(4EH)
Rejection
RJC
(4FH)
:::
Want
10
send
data:
WSD
(40H)
This
message is sent out When data must be
sent
to
a device
at
the
other
end of the interface.
It
contains
data
for the
address and
sire that specify designation and
length,
respectively. of the data to be senL
On receiving a WSD message, the remote device checks its
memory for the speclfied
data
address and size which will
satisfy the
request.
If
it finds them and is ready for
communication, the device will return an "Acknowledge
(ACK)"
message.
Otherwise, it
will
retum
a "Rejection
(RJC)~
message.
Byte
Description
FOH Exclusive
status
41H
Manufacturer
ID
(Roland)
DEY
Device
ID
MDL
Model ID
40H
Commaild
ID
"H
Address
MSB
LSB
"H
Size
MSB
LSB
.om
C!'\ec:',;
.um
F7H
End
of
eKclusive
*
The
size of the data to be
sent
does not indicate
the
number
of
bytes
that
make up a "Data set (OAT)" message, but
represents the
address fields where the
data
should reside.
*Some
models
are
subject to limItations
in
data
fonnat
used
for a single transaction. Requested data, for example, may
have a limit in length or must
be divided into predetermined
address
fields before it is exchanged across the interface.
* The
same
number of bytes comprises address and size data,
which, however,
vary with the Mode! - !D.
*
The
elTOr
checking process uses a checksum
that
provides
a bit
pattern
where
the least significant 7 bits are
zero
when
values for
an
address, size, and thai checksum
ere
summed.
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