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*
The
size
of the
requested data
does
not
indicate the
number
of
byl^
that
will
make
up
a
DTI
message, but represents the address
fields
where
the
requested data
resides.
*
Some
models
are subject to
limitations in
data fonnat used
for
a
single
transaction.
Requeued
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 numt»r
of bytes comprises address
and
size data,
which, however,
vary with the
Mode!
ID.
'
The
error-checking pracf^s
use
a
checksum
that
provides a
bit
pattern
where
the
last
7
bits
are
zero
when
values
for
an
address,
size,
and
thai
checksum
are
summed.
•Data
sell:
DTI
(12H)
This
message
corresponds
to
Ihe 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
bits
of data as well as a
series
of
data fomiafled
in
an
address-dependent
order.
The MID!
standards
inhibit
non
real-time
messages from
interrupting
an
Exclusive
one.
This
fact
is
inconvenient
for
devices
that
support
a
"soft-thm"
function.
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'.
Byte
Description
FOH
Exclusive Status
41H
Manufacturer ID (Roiand)
DEV
Device
ID
MDL
Model
ID
I2H
Command
ID
aaH
1
Address
MSB
1
1
1
LSB
ddH
i
Data
MSB
1
1
1
LSB
sum
Checksum
F7H
End
ot
exclusive
*
A
DTI
message
is
capaUe
of
providing only the
valid
data
among
those
specified
by an
RQ1
message.
"
Some
models
are subject
to limitations in
data
fom»t
used
for
a
single
transaction.
Ret^ested
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 number
of bytes
comprising address data
varies
from one Model
ID
to
another.
'
Hie
error-checking process uses a
diecksum
that
provides a
bit
pattern
where
the
last
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.
I
Dgy
tcB
A^
I
I
Device
B~
{Data
set
1]
^
*
More
Itian
Wm
sec
time
interval.
[Data
set
1
]
*•
(Data
set
1]
•Device B
requesting data
from Device
A
Device B sends an
RQl
message
lo
Device
A,
Checking
the
message, Device
A
sends
a
DTI
message back
to
Device
B.
tPevicB
A
I
I
EiteviceB
I
[Request
data]
{Data
set
i]
>
*
Mora
than
20m
sec
time
interval.
[Data
set
1]
[Data
set
1]
131
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