JP3424818B2 - Music data communication device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-access LAN capable of effectively transmitting MIDI data and the like.

[0002]

2. Description of the Related Art CSMA (Carrier Sense Mu) is used as a LAN system using a multi-access bus.
The single access system is known. In this method, carrier sense is performed to check the presence or absence of a signal on the bus before data transmission, and then transmission is performed. As an improvement of the CSMA method, the CSMA / CD (CS) is configured such that the own station inspects whether a collision has occurred during frame transmission, and the transmission side determines whether the transmission is correct.
MA with Collision Detection
n) method is available. A well-known CSMA / CD LAN is Ethernet (registered trademark). The carrier detection / collision detection method used in these methods does not depend on the format of the frame used, and also the encoding method (if it is within a certain condition).
Do not depend.

[0003]

A bus type LAN like this
For example, if MIDI data is to be sent in the system, it is necessary to store the MIDI message in the data part of the frame according to the frame format used in the system for transmission. But with this,
Since the gateway is made by software, the transmission / reception adapter circuit becomes complicated and expensive. The present invention has been made in consideration of such circumstances, and an object thereof is to provide a multi-access LAN capable of mixing data of different protocols.

[0004]

According to one aspect of the present invention, a music data communication apparatus includes a framing unit that frames music data into a music data frame, and a frame format for the music data frame. It has an addition means for adding a preamble as the protocol shown, and a transmission means for transmitting the music data frame to which the preamble is added to a communication network.

Further, according to another aspect of the present invention, a music data communication apparatus includes a framing means for framing MIDI data in word units to form a MIDI data frame, and a frame format for the MIDI data frame. The protocol includes an adding unit for adding a preamble as a protocol, and a transmitting unit for transmitting the MIDI data frame to which the preamble is added to a network using Ethernet (registered trademark).

[0006]

According to the present invention, a continuous signal or an asynchronous signal is framed, and a preamble for identifying the protocol of the data in the frame is added and transmitted, so that a completely different protocol (signal coding) is provided on the same bus. Method / physical frame format) data is mixed. According to this method, the circuit configuration of the reception adapter is very simple even when MIDI data is sent on the Ethernet, for example.
Also on the transmission adapter side, the circuit configuration is simple because only high-speed processing is required for framing and collision detection / retransmission control. M
Even when processing is performed in IDI message units, this processing can be performed at the MIDI rate (320 μs per byte) and does not require high speed processing.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a main configuration of a bus LAN according to an embodiment of the present invention. Here, general Ethernet is used as a CSMA / CD protocol, and FIG. 1 shows a specific configuration of a transmitting adapter and a receiving adapter for transmitting and receiving MIDI data using the bus. As shown, the MIDI instrument 1 on the transmitting side is connected to the transceiver 4 on the bus via the MIDI cable 2 and the transmitting adapter 3, and the MIDI instrument 5 on the receiving side is connected via the MIDI cable 6 and the receiving adapter 7. It is connected to the transceiver 8 on the same bus.

The transmitting adapter 3 serially / parallel converter 31 converts MIDI data asynchronously generated from the MIDI musical instrument 1 into parallel data, temporarily stores the converted data in the FIFO buffer 32, and then converts it into serial data again. Parallel / serial converter 33, a modulator 34 that encodes the output of the converter 33 and sends it to the bus, and a carrier sense / backoff control circuit 35.
Have. Serial / parallel converter 31 and FIF
The O buffer 32 is provided to frame MIDI data in word units. The carrier sense / back-off control circuit 35 controls the transmission start timing based on the reception signal and the collision detection signal obtained from the transceiver 4.

The receiving adapter 7 includes a demodulation circuit 71 for receiving and demodulating the data placed on the bus transmitted via the MIDI musical instrument 1 and the transmitting adapter 3, a frame length counter 72, and the frame length counter 72. MIDI musical instrument 5 which is controlled and demodulated for each frame
It has a gate circuit 73 for outputting to.

FIG. 2 shows the frame format used in this embodiment. FIG. 2A shows an Ethernet frame format which is a general CSMA / CD protocol. The signal speed is 10 MHz, and the encoding method is bi-phase encoding (Manchester encoding) which is a phase modulation method. The bit pattern of the preamble PA is
As shown in FIG. 2A, 31 10's followed by 1 '
11 of the pieces. DA / SA following the preamble PA
Is a destination / source address, and Length represents the length of data Data. An error check code CRC is attached to the end of the data Data. This code CRC allows the receiving side to remove the abnormal frame.

On the other hand, the MIDI data frame format exchanged between the MIDI musical instruments 1 and 5 is as shown in FIG.
It is as shown in (b). The bit pattern of the preamble PA has 31 0's as shown in FIG.
1 followed by 00. The sign of the preamble of the normal frame is inverted, but the operation of the preamble does not cause any problem. After the preamble PA, 8-bit data bits D0, D1, ..., D7 are sandwiched between a start bit Start and a stop bit Stop, which are one bit at a time. 3
MIDI data (3200 bits on the bus), which is a start-stop synchronization signal for 10 bits, follows at 1.25 Kbps. One bit of MIDI signal is 32 μs, and 320
The same data will be transmitted for each bit.

The operation of transmitting MIDI data will be described below. MIDI / I from MIDI musical instrument 1 to transmitting adapter 3
The MIDI signal input from the N connector is serial /
The data is stored in the FIFO buffer 32 word by word via the parallel converter 31. The carrier sense / back-off control circuit 35 carries out carrier sense, and a signal for one word is taken out from the FIFO buffer 32 by an instruction from this and converted into serial data by the parallel / serial converter 33, and then modulated. It is encoded by the device 34 and transmitted with a preamble. If no collision is detected, the carrier sense / backoff control circuit 3
According to the instruction from 5, the one-word data is discarded from the FIFO buffer 32. When a collision is detected, the carrier sense / backoff control circuit 35 gives an instruction to backoff for an appropriate time and retransmit.

The receiving adapter 7 processes only a frame having a MIDI frame preamble. That is, the demodulation circuit 71 synchronizes the phase of the biphase signal with the MIDI frame preamble, decodes the subsequent biphase signal, and outputs the biphase signal from the MIDI / OUT connector. At this time, the frame length counter 72 is detecting the received frame length.
When the DI frame length is too short (that is, less than 320 μs), the gate circuit 73 is controlled to control the MIDI / O.
The signal output to the UT is forcibly held to 0 until it reaches 320 μs. This prevents the output of a signal that causes a framing error on the receiving side.

Assuming that the f / 2f system, which is frequency modulation, is used as the encoding system on the MIDI signal transmitting side (that is, 0 is a fundamental wave, 1 is a wave having a frequency twice that), the preamble is used. It can be used more effectively. That is, in the case of the f / 2f method, it is not necessary to perform the phase alignment of the bit boundary at the end of the preamble.
The preamble of 000 ... 0001 is used for frames, and 111 ... 1 for MIDI frames.
A preamble of 111 can be used. When such a preamble format is used, in the MIDI frame, the preamble is no longer distinguished from the idle period, and M
The IDI frame receiving side may output the decoded 1 as it is to MIDI / OUT without paying attention to the preamble. If the MIDI transmitting side delays the MIDI / IN signal and encodes and transmits the state of 1 before the start bit, it means that the preamble is transmitted.

In the embodiment, MIDI as an asynchronous signal is used.
The case where the signals are mixed with the CSMA frame of another station in a different frame format has been described, but the present invention is not limited to this and is also effective when modulating and transmitting a continuous signal on an existing Ethernet bus, for example. Is.

[0016]

As described above, according to the present invention,
By adding a simple transmission / reception adapter, it is possible to provide a multi-access LAN capable of transmitting data according to different protocols in a mixed manner.

[Brief description of drawings]

FIG. 1 is a diagram showing a MIDI of LAN according to an embodiment of the present invention.
It is a figure which shows the data transmission / reception part structure.

FIG. 2 is a diagram showing two frame formats of the embodiment.

[Explanation of symbols]

1,5 ... MIDI musical instruments, 2, 6 ... MIDI cables, 3
... Transmission adapter, 4,8 ... Transceiver, 7 ... Reception adapter, 31 ... Serial / parallel converter, 32 ... FIF
O buffer, 33 ... Parallel / serial converter, 34 ...
Modulator, 35 ... Carrier sense / back-off control circuit,
71 ... Demodulation circuit, 72 ... Frame length counter, 73 ... Gate circuit.

Claims (2)

(57) [Claims] 1. A framing means for framing music data into a music data frame, an adding means for adding a preamble to the music data frame as a protocol indicating the frame format, and the music data to which the preamble is added. A music data communication device having a transmission means for transmitting a frame to a communication network. 2. A framing unit for framing MIDI data in word units to form a MIDI data frame, an adding unit for adding a preamble to the MIDI data frame as a protocol indicating the frame format, and the preamble for adding the preamble. And a transmission means for transmitting the MIDI data frame to a network using Ethernet (registered trademark).