Roland JV-30 - Page 60

*
The
size ol the
requested Oala does
not indicate
the number
of bytes
that
will make op
a DTI message,
but
represents the address
fields
where
the
retjuested data resides.
*
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
be divided into
predetermined
address fields
before
it is
exchanged across
the interface.
*
The
same
numlwr of byles
comprises address and
size data,
which,
however, vary with
the Model-ID,
*
The error
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 that
checksum are
summed.
«Data set 1
: 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
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 tor the
devices that
support a
'soft-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.
t
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.
I
Device <A)|
[D8tB sot
I] ^
[Data set 1]
^-
» Mof«
than 20m sec
time Internal.
IData sei 1]
:
^-
[Data set
U
'
^-
Davice
(8)
-(Reguest data]
Byte
Description
FOH
Exclusive
dlK
Manufacturer ID
(Rotend)
oev Device
ID
MDL
h^odel ID
12H Command ID
aa
H
Address MSB
LS6
dc H Da a
it. m Ch BCk
sum
F7H
End of exclusive 1
*
A
DTI message is
capable of providing only the
valid data among
those specified by
an RQl message.
-
*
Some models arc
subject to limitations in data
format used for a
single
transaction. Requested
data, tor example, may
have a limit
in
length or must be
divided into predetermined address
fields before
it is
exchanged across the
interface.
*
The
number ot bytes
comprising address data
varies from one Model-
ID to
another.
*
The error
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 that
checksum are summed.
;
Example of
Message Transactions
*
Device
A
sending data to
Device
B
Transfer of a
DTI message is all that
takes plate.
I
Device (A)
I
I
Device
<6>
|
[Data set 1]
^-
* More than
20m
sec
time internal.
[Data
set 1]
:
^
[Data set 1]
60