Roland VS-840EX Manual Del Usuario página 185

3. One-way Transfer Procedure
This procedure sends out data until it has all been sent and
is used when the messages are so short that answerbacks
need not be checked. For longer messages, however, the
receiving device must acquire each message in time with
the transfer sequence, which inserts 20 milliseconds inter-
vals.
Types of Messages
Mensaje
Datos solicitados 1
Ajuste Datos 1
Request data 1: RQ1 (11H)
This message is sent out when there is a need to acquire
data from a device at the other end of the interface. It con-
tains data for the address and size that specify designation
and length, respectively, of data required.
On receiving an RQ1 message, the remote device checks its
memory for the data address and size that satisfy the
request.
If it finds them and is ready for communication, the device
will transmit a ÒData set 1 (DT1)Ó message, which contains
the requested data. Otherwise, the device won't send out
anything.
Byte Descripción
F0H Estado Exclusivo
41H ID Fabricante (Roland)
DEV ID Aparato
MDL ID Modelo
11H ID Comando
aaH Direcci
:
:
ssH Tama–o MSB
:
:
LSB
sum Suma de cheque
F7H Fin de Exclusiva
* The size of the requested data does not indicate the num-
ber of bytes that will make up a DT1 message, but repre-
sents the address fields where the requested data resides.
* Some models are subject to limitations in data format
used for a single transacci—n. Requested data, for exam-
ple, 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 pattern where the last 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 pro-
cess.
Because every byte in the data is assigned a unique address,
a DT1 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.
ID Comando
RQ1 (11H)
DT1 (12H)
n MSB
ó
:
:
LSB
:
:
The MIDI standards inhibit non real-time messages from
interrupting an Exclusive one. This fact is inconvenient for
devices that support a Òsoft-thruÓ 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 Descripción
F0H Estado Exclusivo
41H ID Fabricante (Roland)
DEV ID Aparato
MDL ID Modelo
12H ID Comando
aaH Direcci
:
:
ddH Datos MSB
:
:
LSB
sum Suma de cheque
F7H Fin de Exclusiva
* A DT1 message is capable of providing only the valid
data among those specified by an RQ1 message.
* Some models are subject to limitations in data format
used for a single transacci—n. Requested data, for exam-
ple, 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, data, and that checksum are summed.
Example of Message Transaccións
¥ Device A sending data to Device B
Transfer of a DT1 message is all that takes place.
Aparato (A)
[Ajuste datos 1]
* M‡s de 20 mseg de tiempo interno.
[Ajuste datos 1]
[Ajuste datos 1]
¥ Device B requesting data from Device A
Device B sends an RQ1 message to Device A.
Checking the message, Device A sends a DT1 message back
to Device B.
Aparato (A)
[Ajuste datos 1]
[Ajuste datos 1]
*M‡s de 20 mseg de tiempo interno.
[Ajuste datos 1]
[Ajuste datos 1]
n MSB
ó
:
:
LSB
:
:
Aparato (B)
Aparato (B)
[Datos solicitados]
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