Roland HP 2700 - Acknowledge Message (ACK); End of Data Message (EOD); Handshake Transfer Procedure

* The size of the requested dala does not indicate the number of bytes
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 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-ID.
* The error checking process uses a checksum that provides a bit pattem
where the least significant 7 bits are zero when values for an address,
size, and that checksum are 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 series of data formatted in an address: dependent order.
The MIDI standards inhibit non-real time messages from interrupting an
exclusive ane. This fact is inconvenient for the devices that support a
“soft-through” mechanism. To maintain compatibility with such devices,
Roland has limited the DT1 to 256 bytes so that an excessively long
message is sent oul in separate segments.
Exclusive
Manufacturer ID (Roland)
Device 1D
Model [D
Command ID
Address MSB
LSB
Check sum
End of exclusive
* A DT1 message is capable of providing only the valid data among
those specified by an RQ! message.
* 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 number of bytes comprising address data varies from one Model-
ID to another.
* The error checking process uses a checksum that provides a bit pattem
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 DT! message is all that takes place.
[Data set 1)
%* More than 20m sec time internal.
[Data set 1} 0 ———————____—___»>
(Data set 1] —————________»>
Roland Exclusive Messages
@ Device B requesting dala from Device A
Device B sends an RQ] message to Device A. Checking the
message, Device A sends a DT! message back to Device B.
(Darter set] ettmmn manne Request data]
[Derter set Pm
* More than 20m sec time internal,
[Data set 1] 0 ———$—_$__—__—__
{Data set 1) ———————-
al Handshake.Transfer Procedure
Handshaking is an interactive process where two 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 retumns
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.
Types of Messages
Went to send data WSD (40H)
Request data RQD (41H)
Data set DAT (42H)
Acknowledge ACK (43H)
End of data EOD (45H)
Communication arror | ERR (4EH)
Rejection RUC (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 ils memory for
the specified data address and size which will satisfy the request. If
it finds them and is ready for communicalion, the device will return
an “Acknowledge (ACK)" message.
Exclusive status
Manufacturer ID (Roland)
Device ID
Model {D
Command ID
Address MSB
LSB
Size MSB
LSB
Check sum
End of exclusive
Otherwise, it will return a “Rejection (RJC)” message.
* 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 ihe 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 bytes comprises address and size data, which,
however, vary wiih the MadellD.
%* 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.
al