Roland D-50 - Page 110

# Data set:
# Request data: ROD (41H)
This message is sent out when there is a need lo acquire data
from a device at the other end of the interface. It contains data
for the address and size thal specify designation and length,
respectively, of data required,
On receiving an RQD message, the remote device checks its
memory for the data address and size which satisfy the request,
If it finds them and is ready for communication, the device will
transmil a “Data sct (DAT)” message, which contains the
requested dala, Otherwise, it will return a "Rejection (RJC)”
message,
Description
Exclusive status
Manvfacturer ID (Roland)
Device 1D
Model 1D
Command ID
Address MSB.
uss
Size MSB
tse
Check sum
End of exclusive
*The size of the requesicd data does not indicate the number
of byles that make up a "Data set (DAT)” message, but
represenis the address fields where the requested data
resides,
%*Some models are subject to limitations in data format used
for a single Uransaction, Requested dala, for example, may
have a limit in length or must be divided into predetermined
address fietds 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 teast significant 7 dils are zero when
values for an address, size, and that checksum are summed.
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 serics of data formatted in an
address~ dependent order,
Although the MIDE standards inhibit non-real time messages
from interrupting an exclusive onc, some devices support a”
soft—through "mechanism = for such interrupts. To
maintaincomputibilily with such devices, Roland has limited the
DAT to 256bytes so that an excessively long message is sent
out in separate scgments,
Exclusive status
Manufacturer ID (Roland)
Device 1D
Model ID
Command ID
Address MSB
Data
Check sum
End of exclusive
# Acknowledge :
#End of data:
*A DAT message is capable of providing only the valid data
among those spccificd by an RQD or WSD 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 pracess 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.
ACK (43H)
This message is sent oul when no error was detected on
reception of a WSD, DAT, "lind of data (EOD)”, or some other
message and a requested setup or action is complete. Unless
it receives an ACK message, the device at the other end will
not proceed to the next operation,
Description
Exclusive status
Manufacturer ID (Roland)
Device ID
Model IO
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 not come to an
end unless ihe remote device returns an ACK message even
though an EOD message was transmilted,
Description
Exclusive status
Manufacturer ID (Roland)
Device iD
Model ID
Command IO
End of exclusive
# Communications error: ERR (4EH)
This message warns the remote device of a communications
fault’ encountered during message transmission due, for
example, to a checksum crror, An ERR message may be
replaced with a "Rejection (RJC)” one, which terminates the
current message transaction in midstream,
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 sending out an RIC message,
Exclusive status
Manufacturer ID (Rotand)
Device 1D
Model ID
Command ID
End of exclusive