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zData
set 1:
*The
size of the requested
data does not indicate the number
of bytes that will make
up а DTI
message, but represents
Ше address fields where the requested data resides.
*Some models are subject to limilalions 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 number of bytes comprises address and size data,
which, however, vary with the Моде! - ID.
*The error checking process uses a checksum
that provides
a bit patlern where the least significant 7 bits are zero when
values for an address, size, and that checksum
are summed.
от
(12H)
This message
corresponds
to the actual data transfer process.
Because every
byte in the data is assigned
a unique
address,
a
ОТ!
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
"soft ~ through"
mechanism.
То
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.
Exctusive
Manufacturer
ID (Roland)
Device
ID
Model
ID
Command
0
Address
MSR
a
ee ashes
ae E
т
Check
sum
End of exclusive
ЖА
DTI
message
is capable of providing
only the уан! data
among
those specified bv ап КО]
message.
*Some
models are subject to limitations in data
format
used
for a single transaction.
Requested.
data, Гог example, may
have à 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
оле
Model ~ ID to another.
* The error
checking
process
uses
a checksum
that
provides
a bit pattern where the least significant
7 hits are zero when
values for an address. size, and that checksum
are summed,
z Example
of Message Transactions
@ Device A sending data to Device В
Transfer of а DT1
message
is all that takes place.
[Data set
Романия
ж More
than
20m
sec
time
interna',
[Data set 1]
———————
—— ——»
———————————
[Data set
1)
@ Device B requesting
data
from
Device
A
Device B sends an RQ!
message
to Device
A. Checking
the
message, Device
A sends
a DTI
message
back
to Device
В.
[Date set 1] -«————— ———————— —Reauest
data]
(B)
[Data set 1]
me
P
* More
than 20m
sec
time internal.
[Data set
1]
——
——
—— —— Be
(Data set
!]
————————
Ё
Handshake - Transfer Procedure |
Handshaking
is an
interactive
process
where
two
devices
exchange
error checking
signals
before
a message
transaction
lakes place, thereby increasing data reliability,
Unlike one - way
transfer
that
inserts
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 MIDI
interface, handshaking
transfer
is
more efficient than one - way
transfer.
Want
10 send
data
WSD
(40H)
Request
data
ROD (ан)
Data
set
DAT
(42H)
Acknowledge
ACK
(43H)
End
of data
EOD
(45H)
Communication
error
| ERR (4ЕН)
Rejection
АЈС (4FH)
= Want to send data:
WSD
(40H)
This message
is sent out when data must be sent (о a device
al the other end of the interface.
Н contains
data
for the
address
and
size
that
specify
designation
and
tengih,
respectively, of the dala
to be sent
On
receiving
а WSD
message,
the remote
device checks
its
memory
lor the specified
data
address
and
size which
will
satisfy
the
request.
If it finds
them
and
is ready
for
communicalion,
the
device
will
retum
ал
" Acknowledge
CACK)"
message.
Otherwise, it will return a
"Rejection.
ЕЈС)"
message.
Description
Exclusive status
Manutacturer
ID (Roland?
Device
ID
Model
ID
Command
0
Address
MSB
MSB
158
Check
sum
End of exclusive
ж The size of the data to be sent does not indicate the number
of bytes that make up a "Data set
(DAT)"
message, but
represents
the address
fields where
the data
should
reside.
*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 number 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.
2]
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