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* The size of the requested data 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 paltern
where the last 7 bits are zero when values for an address, size, and that
checksum are summed.
¢Data set 1: DTI (12H)
This message corresponds to the actual data transfer process.
Because every byte in the data is assigned a unique adress, a DT message
can convey the starting address of one or more bits of 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 devices that support a "soft-thru"
function.
To maintain compatibility with such devices, Roland has limited
the DT1 to 256 bytes so that an excessively long message is sent out in
separate 'segments'
Byte
Description
FOR
Exclusive Status
aH
Manufacturer 1D (Roland}
DEV
Device ID
MDL | Model If)
DH
Command 1D
aalt
Address MSB
}
i}
f
N
|
LSB
ddl
Data
MSB
3
I
i
isB
som
Check sum
WH
End of exclusive
* A DTL message is capable of providing only the valid data among those
specified by an RQI 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 pattern
where the last 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
[Data set 1]
energie
* More than 20m sec time interval.
{Dataset ]] 9 ——————»
De
[Dataset]
* Device B requesting data from Device A
Device B sends an RQI message to Device A.
Checking the message, Device A sends a DT] message back to Device B.
[Request
data]
[Data set]
>
* More than 20m sec time interval
Dataset]
————$———»
[Data set 1)
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