JP3230308B2 - Ring LAN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring type LAN suitable for real-time data communication useful as a LAN for electronic musical instruments.

[0002]

2. Description of the Related Art There has been proposed a LAN for electronic musical instruments in which a plurality of MIDI devices and the like are connected to a ring-type transmission medium to perform mixing and the like. Data used in such an electronic musical instrument LAN includes setup information, performance information, audio sampling information, and the like. These MIDI
Strict real-time performance is required for data communication.

In applications that do not require strict real-time performance, the performance of the ring LAN can be improved in proportion to the signal speed. Simply increase the frame length. Even when the frame length cannot be increased, multi-frame transmission and ETR (Early Token Release)
By adopting the se) method, it is possible to considerably improve the communication performance.

[0004] This point will be described in more detail in the case of the token ring system. In the case of a token ring, it is the transmitting station of the frame that removes the transmission frame from the ring. This is based on the basic requirement that in a ring-type LAN, a frame must always go around the ring in order for each station to be able to receive a transmitted frame. In the simplest token ring, one frame is transmitted by acquiring a token, and the token is released again after the frame is collected (as long as the source address can be determined). In this case, if the frame cannot be collected even after the frame transmission is completed, the token transmission is delayed until the frame is recovered, and an idle pattern is transmitted during that time.

[0005] The existence of such an idle pattern leads to performance degradation with respect to the used signal speed. There is no problem if the frame length is large, but if the frame length is small compared to the ring delay, the idle pattern increases. As a countermeasure, multi-frame transmission and E
The TR method has been considered. The former is a method of transmitting a plurality of frames by one token acquisition. As a result, even when the length of each frame is small, it is possible to secure a large length of the entire continuous frame and improve the performance. The latter is a method in which the token is released after the frame transmission without waiting for the collection of the frame, and the performance can also be improved by this.

[0006]

However, L for electronic musical instruments
In the field of real-time communication such as AN, multi-frame transmission and ETR do not apply. This is because, in the case of token ring, strict priority control and the principle of equal opportunity between stations are hindered in the multiframe transmission and the ETR system. Also, a synchronous LA using a time-division slot multiplexing technique.
Multi-frame transmission in N is also not used for real-time communication because a synchronization frame cannot go around the ring in the required time.

[0007] The present invention has been made in view of the above points, and has as its object to provide a ring-type LAN that improves the communication performance of real-time data.

[0008]

SUMMARY OF THE INVENTION The present invention provides a ring type LAN having a master station for transmitting a frame and a plurality of slave stations for relaying a frame, in which a normal state is set to a bypass state and data transmission is required. have a slave station to transition to the insert state when a insert of the slave stations
The transition to the state starts at the bit boundary after entering the idle period.
It is characterized by being carried out at.

[0009]

According to the present invention, the number of stations connected to the ring can be substantially reduced by bypassing the frame at the slave station that does not perform data transmission. This bypass is performed in a circuit in the office, instead of the user actually plugging and unplugging the connector. Although logically insert / bypass circuit is provided even normal-ring type LAN, in that data receivable state in the bypass state, that the received data is held in a state that is input to the LAN controller in the present invention different. According to the invention,
Without breaking the principle of equal opportunity between stations, and with priority control enabled, it is possible to substantially reduce the time for data to make a circuit on the ring and improve the communication performance of real-time data. . In addition, since the insert / bypass switching is performed in the idle period, it does not affect the operation of the entire LAN. In particular, by performing the switching at the bit boundary, the break of the bit synchronization is prevented.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a master station 1 of a ring LAN according to an embodiment of the present invention, and FIG. Usually, a ring LAN is composed of one master station and a plurality of slave stations. The master station 1 is a station that generates and sends out a frame (which may be a token in token ring), and the slave station 2 is a station that relays the frame, but these need not be fixed assignments. It is possible to provide both functions at the same time and to be able to be any station. However, here, only the components necessary for the master station and the slave station are shown.

[0011] As shown in FIG.
1, a LAN controller 12, an ND (No Data) inserter 13, and a transmitter 14. The LAN controller 12 generates a frame or a token first. The ND inserter 13 generates an idle pattern that determines an idle section having a predetermined length. With such a configuration, the main station 1 transmits a frame (or token, which will be simply described as a frame hereinafter) in which an idle section precedes it, and temporarily stops the frame every time a frame is detected, so that the preceding idle section becomes a predetermined one. Repeat to length. In the case of token ring, only the token is repeated, and the frame passes as it is.

The slave station 2 has a receiver 21, a transmitter 24, an LA
In addition to the N controller 22, there is a switch 23 for switching between an insert state for sending data to the ring and a bypass state for simply bypassing frames flowing on the ring. The switch 23 has a function of switching whether the output of the receiver 21 is transmitted to the ring by the transmitter 24 or the output of the LAN controller 22 is transmitted to the ring while maintaining a state in which the output of the receiver 21 can be input to the LAN controller 22. I do. In order to perform the insert / bypass switching control in synchronization with the idle period, the output terminal of the receiver 21 and the LA
The output terminals of the N controller 22 are provided with idle detectors 25 and 26, respectively. Further, a switching control circuit 27 is provided which is controlled by the outputs of the idle detectors 25 and 26 and performs insert / bypass switching control.

As an example of real-time communication, when a LAN for an electronic musical instrument is specifically configured, a MIDI device or the like is connected to the LAN controller of each station via a MIDI cable.

The data delay at the station includes a transmission line delay due to a transmission characteristic of a cable or a connector, a delay at a transmitter or a receiver (including a delay for clock synchronization), and a delay at a LAN controller. There are three delays associated with protocol processing. In the case of this embodiment, as is apparent from the configuration of FIG. 2, it is considered that the delay in the LAN controller 22 is reduced to zero. However, in consideration of the fact that some stations are dedicated to reception, in this embodiment, even if bypassed,
The received data is input to the LAN controller 22.

The operation of the ring type LAN according to this embodiment will be specifically described with reference to FIG. FIG. 3 shows a state of data flowing on the ring in a normal state, a state after insertion, and a state after bypass. The data flowing on the ring as shown is either a frame or an idle. Although not shown in detail, the frame is surrounded by a special bit string indicating its boundary. The idle section is set to a length larger than the maximum value of the delay of the LAN controller unit of each station connected to the ring. This is because a portion for absorbing the reduction of the ring length due to the bypass (if it is allowed to simultaneously bypass N stations in one idle section, it is necessary to take N times the length) and a so-called preamble Consisting of

The slave station is set in a normal state and in a bypass state by the switch 23. Then, when data transmission becomes necessary, the state shifts to the insert state in the idle period. This switching is performed immediately after entering the idle section as shown in FIG. 3, that is, at a bit boundary in the idle section. At this time, the ND inserter 13
Causes an idle pattern to be inserted. Conversely, when data transmission becomes unnecessary, the inserted slave confirms that there is an idle section after the frame, and then shifts to the bypass state in the idle section. At this time, all of the lost bit strings are in the idle section, and the frames before and after are not destroyed.

The timing of the insert / bypass switching described above is detected by two idle detectors 25 and 26 which detect and output an idle period.
The two idle detectors 25 and 26 are provided to measure the station delay time. Both can be bypassed when both are detecting the idle period, and the receiver 2
Insertion is possible when the idle detector 25 on one side detects an idle section.

The clock used in the station is supplied to the receiver 21
In, the clock of the input signal is converted into its own clock. Therefore, from the receiver 21 and from the LAN
The bit strings from the controller 22 have the same phase,
Switching by the switch 23 is correctly performed at a bit boundary. Therefore, the bit synchronization of the input signal at the downstream station is not lost.

When considering the actual use environment of the ring type LAN, there are many cases where stations that do not transmit data are connected to the ring. The first case is when a station that is not used at all is connected. Once wired, it is cumbersome to unplug and reconnect the cable and rewire it, often leaving it alone. The second is a case of a station dedicated to reception. The ring LAN originally has high reliability of the transmission path,
When real-time transmission is considered, the data is dripped. In such a case, the receiving-only station only needs to repeat the signal at all times, and the LAN controller only needs to capture and process the signal. Third, there is a case where some stations do not transmit for the time being. Stations do not always transmit data. Data transmission is performed in a certain section and is usually silent without data transmission. In such a case, a station that does not perform real-time transmission is allowed to delay the data transmission response. According to this embodiment, by a bypass in station that does not perform data transmission as described above, connected to the ring
The number of stations to be transmitted is substantially reduced, so that the time required for a signal to make a round of the ring is shortened, and the communication performance of real-time data is improved.

Note that a register insertion ring is known as a ring type LAN which is seemingly similar to the system of this embodiment. In this register insertion ring, the normal signal is repeated, and the station transmitting the data temporarily stores the input data in the register, transmits the contents of this register after the frame transmission is completed, and repeats the signal again. Return to the state. However, in this embodiment, the bypass / insert switching is not directly related to the packet, but merely switches whether or not to participate in the ring, and the data transmission is performed according to the protocol of the inserted ring LAN. , Is basically different from the register insertion ring.

[0021]

As explained above, according to the present invention,
By providing the slave station with switching means for switching between the frame insertion state and the bypass state in synchronization with the idle period while maintaining the data receivable state, it is possible to obtain a ring-type LAN with improved real-time data communication performance. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main station configuration of a ring LAN according to an embodiment of the present invention.

FIG. 2 is a diagram showing a slave station configuration of the ring LAN according to the embodiment.

FIG. 3 is a diagram showing a state of data transmission in the embodiment.

[Explanation of symbols]

1 ... master station, 11 ... receiver, 12 ... LAN controller,
13 ND inserter, 14 transmitter, 2 slave station, 21 receiver, 22 LAN controller, 23 switcher, 2
4. Transmitter, 25, 26 ... Idle detector, 27 ... Insert / bypass switching control circuit.

Claims (1)

(57) [Claims] In a ring type LAN having a master station for transmitting a frame and a plurality of slave stations for relaying a frame, a normal state is set to a bypass state, and when data transmission becomes necessary, an insert state is set. have a transition to the slave station, the transition to the insert status of the slave station, the idle section
A ring-type LAN, which is performed at a bit boundary after entering .