User manual ROLAND VGA-7 MIDI IMPLEMENTATION V1.00

[. . . ] BANK PROG MSB LSB CHG VGA-7 --- --- --- ----0 0 41 U41 0 0 42 U42 0 0 43 U43 0 0 44 U44 0 0 45 U45 0 0 46 U46 0 0 47 U47 0 0 48 U48 0 0 49 U49 0 0 50 U40. 0 0 51 U51 0 0 52 U52 0 0 53 U53 0 0 54 U54 0 0 55 U55 0 0 56 U56 0 0 57 U57 0 0 58 U58 0 0 59 U59 0 0 60 U50. 0 0 61 U61 0 0 62 U62 0 0 63 U63 0 0 64 U64 0 0 65 U65 0 0 66 U66 0 0 67 U67 0 0 68 U68 0 0 69 U69 0 0 70 U60. 0 0 71 U71 0 0 72 U72 0 0 73 U73 0 0 74 U74 0 0 75 U75 0 0 76 U76 0 0 77 U77 0 0 78 U78 0 0 79 U79 0 0 80 U70. [. . . ] <Example> What is the decimal equivalent of 5AH?From the above table, 5AH = 90. Examples of actual MIDI messages <Example> C0 32 CnH is the Program Change status and oIis the MIDI channel number. Since 0H = 0, and 32H = 50, this is a Program Change message of MIDI CH = 1, Program number 50. Examples of exclusive messages and calculating the checksum Roland exclusive messages (DT1) are transmitted with a checksum at the end of the data (before F7) to check that the data was received correctly. The value of the checksum is determined by the address and data (or size) of the exclusive message. How to calculate the checksum (hexadecimal values are indicated by a following "H") The checksum consists of a value whose lower 7 bits are 0 when the address, size and checksum itself are added. The following formula shows how to calculate the checksum when the exclusive message to be transmitted has an address of aa bb cc ddH, and data or size of ee ffH. aa + bb + cc + dd + ee + ff = total total / 128 = quotient . . . remainder 128 - remainder = checksum Checksum is 0 if the remainder is 0. 6 Roland Exclusive Messages 1. Data Format for Exclusive Messages Roland's MIDI implementation uses the following data format for all Exclusive messages (type IV): Byte F0H 41H DEV MDL CMD [BODY] F7H Description Exclusive Status Manufacturer ID (Roland) Device ID Model ID Command ID Main data End of exclusive ·One-way transfer procedure (See Section 3 for details. ) This procedure is suited to the transfer of a small amount of data. It sends out an Exclusive message completely independent of the receiving device's status. Connection Diagram Device A MIDI OUT MIDI IN 1 2 Device B MIDI IN MIDI OUT Connection at point 2 is essential for "Request data" procedures. (See Section 3. ) ·MIDI status: F0H, F7H An Exclusive message must be flanked by a pair of status codes, starting with a Manufacturer ID immediately after F0H (MIDI version 1. 0). ·Handshake-transfer procedure (This device does not use this procedure) 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 MIDI OUT MIDI IN 1 2 Device B MIDI IN MIDI OUT ·Manufacturer ID: 41H The Manufacturer ID identifies the manufacturer of a MIDI instrument that sends an Exclusive message. Value 41H represents Roland's Manufacturer ID. ·Device ID: DEV The Device ID contains a unique value that identifies individual devices in the implementation of several MIDI instruments. It is usually set to 00H­0FH, a value smaller by one than that of a basic channel, but value 00H­1FH may be used for a device with several basic channels. Connection at points 1 and 2 is essential. Notes on the above procedures * There are separate Command IDs for different transfer procedures. * 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. ·Model ID: MDL The Model ID contains a value that identifies one model from another. Different models, however, may share an identical Model ID if they handle similar data. The Model ID format may contain 00H in one or more places to provide an extended data field. The following are examples of valid Model IDs, each representing a unique model: 01H 02H 03H 00H, 01H 00H, 02H 00H, 00H, 01H 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 intervals. Types of Messages Message Request data 1 Data set 1 Command ID RQ1 (11H) DT1 (12H) ·Command ID: CMD The Command ID indicates the function of an Exclusive message. [. . . ] 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 F0H 41H DEV MDL 12H aaH | | ddH | | sum F7H Data Description Exclusive Status Manufacturer ID (Roland) Device ID Model ID Command ID Address MSB | | LSB MSB | | LSB Check sum End of exclusive * 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 transaction. [. . . ]