Roland FC-300 Bedienungsanleitung PDF herunterladen (Seite 60)

Equipement MIDI (en anglais)

Handshake-transfer procedure

(This device does not use this procedure)

This procedure initiates a predetermined transfer sequence (handsha-

king) across the interface before data transfer takes place.

Handshaking ensures that reliability and transfer speed are high

enough to handle a large amount of data.

fig.Connection-Diagram2.eps

Connection at points 1 and 2 is essential.

Notes on the above procedures

• There are separate Command IDs for different transfer procedu-

res.

•Devices A and B cannot exchange data unless they use the same

transfer procedure, share identical Device ID and Model ID,

and are ready for communication.

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 chec-

ked.

For longer messages, however, the receiving device must acquire each

message in time with the transfer sequence, which inserts 20 millise-

conds intervals. In this method, as for the receiving device, it is neces-

sary to receive data correctly in time.

Types of Messages

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 contains 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 trans-

mit a “Data set 1 (DT1)” message, which contains the requested data.

Otherwise, the device won’t send out anything.

• The size of the requested data does not indicate the number of

bytes that will make up a DT1 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

pattern where the last 7 bits are zero when values for an

address, size, and that checksum are summed.

Device (B)

MIDI IN

MIDI OUT

Device (A)

MIDI OUT

MIDI IN

3. One-way Transfer Procedure

Message Command ID

Request data 1 RQ1 (11H)

Data set 1 DT1 (12H)

Byte Description

F0H System Exclusive Status

41H Manufacturer ID (Roland)

DEV Device ID

MDL Model ID

11H Command ID

aaH Address MSB

: :

Address LSB

ssH Size MSB

: :

Size LSB

sum Check sum

F7H EOX (End of System Exclusive)

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