Roland S-330 Owner's Manual page 153

*Thc
size
of
the"
requested data docs
not indicate ihe numlx,-r
of bytes that
will
make up
a
DTI message, but represents
the address fields
where
the requested data
resides.
Some
models arc 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 bytes comprises address
and
size data,
which,
however, vary with
the
Model
-11).
*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
arc
summed.
#
Data
set
1
:
DT1
(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 scries 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.
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
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
RQ1
message.
Some
modeti arc subject to limitationi
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 number
of
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
place.
I
Device (A)
I
[Data set
1]
»-
*More
than
20m
sec time
internal.
[Data
set 1]
I
Device (B)l
[Data
set
1]
•
Device
B
requesting data
from Device
A
Device
15
sends an
RQ1 message
to Device A.
Checking
Ihe
message, Device
A
sends
a
DTI message back
to
Device
B.
[Data
set
1]
[Data
set
1]
I
Device (B)
I
-[Request data]
*More
than
20m
sec time internal.
[Data set
1]
[Data
set 1]
|j|Handshake- Transfer Procedure]
Handshaking
is
an interactive process
where
I
wo
devices
exchange
error
checking signals before a
message
transaction
takes
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
mure
efficient
than
one— way
transfer.
Types
of
Messages
Message
Command
ID
Want
to
send data
WSD
(40H)
Request data
ROD
(41H)
Data set
DAT
(42H)
Acknowledge
ACK
(43H)
End
of data
EOD
(45H)
Communication
error
ERR
(4EH)
Rejection
RJC (4FH)
#
Want
to
send data
:
WSD
(40H)
This
message
is
sent
out
when
data must be sent to
a device
at
the other
end
of the interface.
It
contains data for the
address
and
size that specify
designation
and
length
respectively, of
the data
to
be
sent.
On
receiving a
WSD
message, the remote device
checks
its
memory
for the specified
data address and
size
which
will
satisfy the request.
If it
finds
them and
is
ready for
communication,
the
device
will
return an
"Acknowledge
(ACK)" message.
Otherwise,
it
will
return a "Rejection (RJC)"
message.
Byte
Description
FOH Exclusive status
4IH Manufacturer
ID
(Roland)
DEV
Device
ID
MDL Model
ID
40H
Command
ID
aaH
Address
MSB
LSB
ssH Size
MSB
LSB
sum Check sum
F7H End of exclusive
*The
size of
the data
to
be sent docs 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
inlo
predetermined
address
fields
before
it
is
exchanged
across the interface.
*The same number
of
bytes comprises address and
size
da
la,
which,
however, vary with the
Model-
II).
*The
error checking process uses a
checksum
that
provides
a bit
pattern
where
the least significant 7
bits art-
zero
when
values
for
an address,
size,
and
that
checksum
nre
summed.