Roland D-50 - Page 108

Roland Exclusive Messages
7. (ES Format for Exclusive Messages}
Roland's MIDI implementation uses the fotlowing data format
for all exclusive messages (type IV):
Description
FOH Exclusive status
41H Manufacturer ID (Roland)
DEV Device ID
MOL Model ID.
CMO Command iD
(BODY) Main data
FU End of exclusive
# MIDI status. FOH, F7H
An exclusive message must be flanked by @ pair of status
codes, starting with a Manufacturer—ID immediately after FOH
(MIDI version |.0),
# Manufacturer- ID: 41H
‘The Manufacturer—ID identifies the manufacturer of a MIDE
instrument that triggeres an exclusive message. Value 41H
represents Roland's Manufacturer~ID.
# Device- ID: DEV
The Device-I1} contains a unique value that identifies the
individual device in the multipte implementation of MIDI
instruments, ft is usually set to OOH — OFH, a value smaller
by one than that of a basic channel, but value 00H — 1FH
may be used for a device with multiple basic channels.
# Model- 1D: MDL
The Model~ID contains a valuc that uniquely identifies one
model from another, Different miodels, however, may share an
identical Modet—1D if they handle similar dala.
‘The Model—1D format may contain 00H in one or more places
to provide an extended data field. The following are examples
of valid Model—IDs, cach representing a unique model :
On
02H
03H
OO, O11
OOH, 0211
OOH, GOH, OL
# Command- ID: CMD
The Command~1D indicates the function of an exclusive
message. The Command-ID format may contain 00H in one
or more places to provide an extended data field. The
following are examples of valid Command-1Ds, each
representing a unique function :
Oilk
O2H
O3H
OOH, OH
O08, O2H
OOH, OOF, O18
# Main data: BODY
‘This field contains a message to be exchanged across an
interface. The exact data size and contents will vary with the
Model-1) and Command--1D,
Ea[Acdress- mapped Data Transfer
Address mapping is a technique for transferring messages
conforming to the dati format given in Section I, it assigns
a series of memory—sesident records——waveform and tone
data, switch status, and parameters, for example—~to specific
locations in a machine~dependent address space, thereby
allowing access to data residing at the address a message
specifics,
Address~ mapped data transfer is therefore independent of
models and data catcgories. ‘This technique allows use of (wo
different transfer procedures : one~way transfer and
handshake transfer.
# One- way transfer procedure (See Section3 for details)
This procedure is suited for the transfer of a small amount of
data. It sends out an exclusive message completely independent
of a receiving device status,
Connection Diagram
Device (A)
Device (B)
NADL OUT
MIL I
Connectionat point2 is essential for "Request data” procedures,
Gee Section.)
# Handshake- transfer procedure (See Section4 for details)
This procedure initiates a predetermined transfer sequence
(handshaking) 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,
Connection Diagram
Device (A) Device (8)
1
| oe 2 |
Connectionat points! and 2 is essential.
Notes on the above two procedures
There are separate Command--IDs for different transfer
procedures,
%*DevicesA and B cannot exchange data unless they use the
same transfer procedure, share identical Device—ID and Model
ID, and are ready for communication,
El[one- way Transfer Procedure
This procedure sends out data all the way until it stops when
the messages are so short that answerbacks need not be
checked,
For long messages, however, the receiving device must acquire
each message in time with the teansfer sequence, which inserts
intervals of at least 20milliseconds in between.
Types of Messages
Message Command ID
Request data 1 | RQ? (11H)
Data set i DTI (12H)
# Request data #1: RQ1 (11H)
This message is sent oul 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 thal specify designation and length,
respectively, of dala required.
On receiving an RQI 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 “Data set | (DT1)" message, which contains the
requested data, Otherwise, the device will send out nothing,
Exclusive status
Manufacturer tD (Roland)
Device ID
Model 1D
Command iD
Address MSB
Check sum
End of exclusive