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# Request
data -
ROD
(47H)
This message
is sem
cut
when
there is a need to acquire data
from a device at the other end of the interf
kt contains data
for the address
und
size
that
specify
designation
and
length,
respectively, of dati
required,
On
receiving
an
RQD
message,
the remote
device
checks
its
memory
for the dala address and size which satisfy (he request.
If it finds them and is ready
for communication, the device will
transmit
a "Data set
CDAT)"
message, which contains the
requested
dala,
Otherwise,
it will
return
a "Rejection
(RJC)"
message.
Desernption
Exclusive
status
Manufacturer
ID (Roland)
Device
ID
Mode!
ID
Command
iD
Address
MSB
LSB
Size
MSB
LSB
Check
sum
End
of exclusive
*The size of the requested
data does not indicate the number
of bytes
that
make
up a "Duta
set
(DAT)"
message, but
represents
the
address
fields
where
the
requested
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 tength 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 Model~ID,
*The
error
checking;
process
uses
a checksum
that provides
a bit pattern where the Ieast significant 7 bits are zero when
values
for an address, size, and
that checksum
are summed.
# Data set:
DAT
(42H)
This message
corresponds
to the actual
data
transfer
process.
Because
every
byte in the data
is assigned
a unique address,
the
message
can convey
the starting
address
of one or more
data
as
well
as
a
series
of
data
formatted
in
an
address
~ dependent:
order,
Although
the MIDI
standards
inhibit
non-real
time
messages
from
interrupting
an exclusive
one, sume
devices
support
a "
soft=throaugh "=
mechanism
= for
such
interrupts .
To
maintaincompatibilily
with such devices, Roland
has limited the
DAT
to 256bytes
so that an excessively
long message
is sent
out in separale segments.
Description
Exclusive
status
Manufacturer
ID (Roland)
Device
ID
Modet
10
Command
ID
Address
MSB
Check
sum
End
of exclusive
# Acknowledge
:
# End of data:
# Communications
error :
*A
DAT
message
is capable
of providing
only the vatid data
among
those specified
by an
RQD
or
WSD
message.
%*Some
models
are
subject
to limitations
in dats
format
used
for a single
transaction,
Requested
data, far
example,
may
have 3 limit in length or must
be divided into predetermin
address
fields before
it is exchanged
across
ihe interface.
*The
number
of bytes comprising
address
data
varies
from
one
model
[D to another.
*The
error
checking
process
uses
a cheeksum
that
pravic
a bil pattern where the
st significant 7 bits are zero whe
values
for an address, size, and that checksum
are summed.
ACK
(43H)
This
message
is sent
out
when
no
error
was
detected
on
reception of a WSD, DAT, "End of data
(EOD)", or some other
message
and a requested
setup or action
is complete.
Unless
it receives an
ACK
message, the device
al
the other
end
will
not proceed
to the next
operation,
Exclusive
status
Manufacturer
10 (Roland)
Device
ID
Model
ID
Command
ID
End
of exclusive
EOD
(45H)
This message
is sent out to inform: a remote device of the end
of a message.
Communication,
however,
will aot come
to an
end
unless
the remole
device returns
an
ACK
message
even
though
an
EOD
message
was
transmitted,
Exclusive
status
Manufacturer
ID (Roland)
Device
1D
Model
ID
|
Command
(D
End
of exclusive
ERR
(4EH)
This message
warns the remole device of a communications
fault
encountered
during
message
transinission
due,
for
example,
to a checksum
error,
An
ERR
message
may
be
replaced with a "Rejection
(RJC)"
one, which terminates the
current
message
transaction
in midsiream,
When
it receives
an
ERR
message,
the sending
device
may
either attempt
to send out the last message
a second
time or
terminate
communication
by sendin,
out an
RIC
message.
Exclusive
status
Manufacturer
1D (Roland)
Device
iD
Model
ID
Command
ID
End of exchisive
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