Roland JV-80 Owner's Manual page 198

Roland
Exclusive
Messages
*
The
size of the requested data
does
not indicate the
number
of
bytes
that will
make
up
a
DT)
message, but represents the address
fields
where
the requested data
resides.
* Some
models are subject (o limitations
in
data format used
for
a
single transaction.
Requested
data, for
example,
may
have
3
limit
in
length or
must
tie
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 Model-ID.
*
The
error checking process uses a
checksum
thai
provides a
bit
pattern
where the
least significant
7
bits
are zero
when
values
for
an
address,
size,
and
that
checksum
are
summed.
#Data
set
1
:
DTI (12H)
This message corresponds
to the actual
data
transfer process.
Dccause every byte
in
the data
is
assigned a unique address, a
DTI
message can convey
the
starting
address of one or
more
data as well
as a
series
of data formatted
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
"sofl-through" mechanism.
To
maintain
compatibility
with such devices.
Roland has
limited the
DTI
to
256 bytes so
that
an excessively long
message
is
sent out
in
separate segments.
•
Device B requesting data from Device
A
Device B
sends
an RQl message
to
Device A. Checking
the
message. Device
A
sends
a
DTI message back
to
Device
B.
Device (A)
Device
(8)
[Data s«t 1]
-^
[Request
data]
[Data
set
1]
^-
« More than
20m
sec time internal.
[Data set
1]
;
*-
[Data set
1J
'
^-
Byte
De
so
r
lotion
FOH
Exclusive
41H Manufacturer
ID
(Roland)
DEV
Device ID
MDL
Model ID
12H
Command
ID
aaH Address
MSB
LSB
ddH
Data
sum
Check
sum
F7H End
of exclusive
* A DTI
message
is
capable of providing only
the valid
data
among
those specified
by an
RQJ
message.
* Some
models
are subject to limitations in
data format used
for a
single transaction.
Requested
data, for
example,
may have
a
limit
in
length or
must
l>e
divided into predetermined address
fields
before
it
is
exchanged
across the interface.
*
The number
of bytes comprising address data varies from
one
Model-
ID
to
another.
*
The
error checking process uses a
checksum
thai
provides a
bit
piittcrn
where
the
least significant
7
bits
are zero
when
values
for
an
address,
size,
and
that
checksum are
summed.
#
Example
of
Message Transactions
*
Device
A
sending data
to
Device B
Transfer
of a
DTI
message
is all
that
takes
place.
Device (A) Device
(B)
[Data
set I)
^-
* More
than
20m
sec time
internal.
[Data
set 1]
[Data set
1]
198