JPH06276199A - Multiplex transmitter - Google Patents

Abstract

PURPOSE:To reduce a modification degree from a media access controller and to simplify a transmission state mechanism by enabling synchronous detection during a transmission processing without letting collision detection be an asynchronous event. CONSTITUTION:When an own station detects collision while transmitting signals, a transmission limiting circuit 252 does not perform the operation of a CARRI ER (0) being outputted to the media access controller 23. Then, the CARIER (I) from a transmission line signal controller 22 is passed through as it is and inputted to the controller 23. That is, when COLLISION (collision detection signal) is turned to an ON state while TRNENEBLE from the controller 23 is in the ON state, the transmission limiting circuit 252 passes the CARRIER (I) from the controller 23 through as it is thereafter as well. Then, by imparting as the CARRIER (0) to the controller 23, transmission limiting is not performed. Thus, the modification degree from the media access controller of a CSMA/CD system is reduced and the transmission state mechanism can be simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex transmission device used for multiplex communication, and more specifically, a new transmission line control device for simplifying a transmission control logic. The present invention relates to a multiplex transmission device including a transmission limiting device.

[0002]

[Prior Art] CSMA / CD (Carrier Sense Multiple Acce
A media access control method called ss with Collision Detection) has been put into practical use. This is the LAN (L
Ocal Area Network) access method, and access control is performed by the following procedure.

When transmitting a signal, each station connected to the transmission line checks whether or not there is a signal on the transmission line, in other words, whether or not another station is actually transmitting the signal, and the signal is transmitted on the transmission line. If this is detected, it means that the signal transmission by another station is actually being performed, so the system waits until the signal transmission is completed. If there is another station that simultaneously transmits a signal from a certain station, the signals transmitted from multiple stations will collide on the transmission path.In this case, the signal on the transmission path will collide. A collision is detected from the waveform. When a collision is detected, the transmitting station retransmits after waiting time determined according to a predetermined algorithm.

The standby time is defined by the following equation according to the number of collisions in the standard IEEE 802.3 standard. Standby time = slot time x r where r: uniform random number in the range of 0 ≤ r ≤ 2 ^m-1 m = min (i, 10) i: number of collisions The standard value of slot time is 51.2 μsec. Yes, and if there are 16 consecutive collisions, the signal transmission is aborted.

In such a conventional CSMA / CD system, the probability of continuous collision increases as the amount of traffic, that is, the amount of communication increases. The waiting time is shortened, and the probability of successful signal transmission by retransmission is increased.
Therefore, the generation order of the signals to be transmitted and the transmission success order are significantly different.

In view of such problems of the conventional CSMA / CD system, for example, the Institute of Electronics, Information and Communication Engineers Technical Report IT-90-17 (1990)
(July, 2013) and Japanese Patent Laid-Open No. 3-117052, a media access control method called a retransmission limited CSMA / CD method is proposed. In this retransmission limited CSMA / CD system, when a collision occurs, the stations that are not involved in the collision generate the earlier signal by stopping the signal transmission until the successful transmission by the station involved in the collision is completed. It is possible to improve the probability of successful transmission prior to the above-mentioned signal, and reduce the spread of the time distribution required for signal transmission.

Communication device adopting general CSMA / CD
The (station) is configured as shown in the block diagram of FIG. In FIG. 5, reference numeral 1 is a transmission line,
Each station is connected by a transceiver 11.

Reference numeral 3 indicates a computer / terminal,
It is the original subject of communication. This computer / terminal 3 is LLC (Lo
gical Link Control) Executes communication protocol control and application programs of layers above. CP for this computer / terminal 3
A U 31 and a memory 32 are provided.

Reference numeral 2 indicates a CSMA / CD communication control device, which controls communication between the computer / terminal 3 which is the main body of communication and the transmission line 1 which is a medium. The CSMA / CD communication control device 2 includes a communication control management device 21, a transmission line signal control device 2
2, a media access control device 23 and a bus interface device 24 are provided. Communication control management device 21 is CSMA / CD
It manages management such as initialization in the communication control device 2.

The bus interface device 24 is connected between the computer / terminal 3 and the media access control device 23, and exchanges control signals and data between the CSMA / CD communication control device 2 and the computer / terminal 3. Control The media access control device 23 receives a transmission request from a host device, in this case, the computer / terminal 3 via the bus interface device 24,
Transmission control is performed according to the control method of the MAC (Media Access Control) layer, and a lower-level device, in this case, a transmission line signal control
It receives the received data from 22 and sends it to the computer / terminal 3 which is the host device.

The transmission path signal control device 22 sends the transmission data string sent from the media access control device 23 to the transceiver 11, and conversely sends the data string received from the transceiver 11 to the media access control device 23. In addition, when the transceiver 11 notifies that the signal waveform on the transmission path 1 is disturbed, the transmission path signal control device 22 notifies the media access control device 23 as a collision detection.

The interface between the media access controller 23 and the transmission path signal controller 22 is constructed as shown in the block diagram of FIG. RCV-CLOC from the transmission line signal controller 22 to the media access controller 23
K (reception data synchronization clock), RCV-DATA (reception data serial line), CARRIER (carrier signal), COLLISION (collision detection signal), TRN-CLOCK (transmission data synchronization clock) are sent to control media access. TRN-DATA (transmission data serial line) and TRN-ENEBLE (transmission permission signal) are sent from the device 23 to the transmission path signal control device 22, respectively.

RCV-CLOCK is a rectangular wave signal output from the transmission path signal control device 22 to the media access control device 23, and the transmission path signal control device 22 receives data (bit string).
Is used as a bit synchronization signal when being transmitted to the media access control device 23.

RCV-DATA is reception data output from the transmission path signal control device 22 to the media access control device 23 as a bit string, and is synchronized with RCV-CLOCK described above. CARR
The IER is turned on (active) when there is a signal on the transmission path 1 and is output from the transmission path signal control device 22 to the media access control device 23. Media access control device
It means a transmission delay instruction and a reception start instruction to 23.

COLLISION is turned on (active) when a collision is detected on the transmission line 1, and is output from the transmission line signal control device 22 to the media access control device 23.
TRN-CLOCK is a rectangular wave signal that is always output from the transmission path signal control device 22 to the media access control device 23, and is used as a bit synchronization signal when sending transmission data (bit string) from the media access control device 23. To be done.

TRN-DATA is a media access control device 23
The transmission data is transmitted from the transmission path signal control device 22 as a bit string, and is synchronized with the above-mentioned TRN-CLOCK. TRN-
ENABLE is data transmitted from the media access control device 23.
Transmission of (bit string)
It is turned on (active) to notify 22 and is output from the media access control device 23 to the transmission path signal control device 22 during transmission of the above-mentioned transmission data (TRN-DATA).

When performing the media access control adopting the above-mentioned retransmission limited type CSMA / CD system with such a conventional configuration, the table 1 in the media access control device 23 is shown.
And by incorporating control logic based on a transmission state mechanism including a transmission restriction function as shown in Table 2.

[0018]

[Table 1]

[0019]

[Table 2]

The contents of Tables 1 and 2 are as follows.
The items marked with “◎” in the following items are the conventional CSMA / C shown in Table 3 and Table 4 below.
This item is common to the transmission status mechanism of D-type media access control.

* Explanation of Event [Event from Management Unit] ◎ Initialization: Generated by the management unit to enable the transmission media access control unit.

[Event from upper layer] ◎ Data request: Generated after frame is assembled after transmission data is generated in the upper layer.

[Event from Lower Layer] ◎ Carrier ON: Indicates that the physical layer signal control unit senses the medium and changes from no carrier to present. ◎ Carrier off: Indicates that the medium has been carrier sensed by the physical layer signal control unit and changed from having carrier to having carrier.

Collision detection: Generated when the physical layer signal control unit detects contention on the medium.
This event occurs between carrier on and carrier off, and the media access control unit can always detect this event asynchronously.

[Internal Event] ○ Preamble transmission completion: Generated when the preamble transmission is completed. ◎ Transmission completed: Generated when frame transmission is completed. ◎ Jam transmission completed: Generated when the transmission of jam bit string is completed.

Excessive collision at the completion of jam transmission: The trial counter reaches the maximum number of trials within the limit and is generated when the transmission of the jam bit string is completed. ◎ Delay timeout: Generated when the interframe spacing delay timer times out. ○ Deadlock monitoring timeout: Generated when the deadlock monitoring timer times out.

* Description of status values ◎ START: Status where initialization is not completed. ◎ IDLE: The state where there is no transmission frame, the medium is empty, and data transmission is not stopped. ○ Preamble transmission (PREAMMBLE TRANSMIT): A state in which a preamble bit string is being transmitted.

○ Preamble transmission collision detection (PREAMMBLE
TRANSMIT COLLISION): After the collision is detected, the preamble bit string is being sent. ◎ Transmit (TRANSMIT): A state in which a bit string of data is being sent. ◎ Jam: A state in which a jam bit string is being sent. ◎ Busy postponement without request for transmission (DEFER NO WAIT): The medium is busy with no transmission frame. ◎ Busy postponement with transmission request (DEFER WAIT): The transmission frame is held and the medium is busy.

◎ Delay without requesting transmission (DELAY NO WAI
T): A state in which inter-frame spacing is in progress without a transmission frame. ◎ Delay with transmission request (DELAY WAIT): A state where there is a transmission frame and inter-frame spacing is in progress. ○ Transmission limit without transmission request (LIMIT NO WAIT): A state where there is no transmission frame and transmission after collision is limited. ○ Transmission limit with transmission request (LIMIT WAIT): A state where there is a transmission frame and transmission after collision is limited.

* Description of operation ◎ Initialization execution: Stop all timers, reset all internal variables, and wait for carrier off. ◎ Start transmission of preamble: Start transmission of preamble bit string. ◎ Start data transmission: Starts transmitting the data bit string after the preamble. ◎ Jam transmission start: Starts sending jam bit strings.

Display of successful transmission: Notifies that the frame has been successfully transmitted. ◎ Transmission failure display: Notifies that the frame transmission failed. ◎ Trial counter addition: Add to the counter that records the number of trials of the same frame. ◎ Trial counter reset: The counter recording the number of trials of the same frame is initialized to 0.

Start delay timer: Calculate the delay time of spacing between random frames and set the delay timer to that value. ◎ Delay timer stop: Stop the delay timer. ○ Start deadlock monitoring timer: Set the deadlock monitoring timer to the value of deadlock monitoring time. ○ Deadlock monitoring timer stop: Stop the deadlock monitoring timer.

For reference, the conventional CS without transmission restriction
The transmission status mechanism of MA / CD media access control is shown in the schematic diagrams in Tables 3 and 4.

[0034]

[Table 3]

[0035]

[Table 4]

The contents of Tables 3 and 4 are as follows.
The items marked with “◎” in the following items are the transmission status mechanism of the conventional retransmission limited CSMA / CD method media access control shown in Table 1 and Table 2 above. It is a common item.

* Explanation of Event [Event from Management Unit] ◎ Initialization: Generated by the management unit to enable the transmission media access control unit.

[Event from Upper Layer] ◎ Data Request: Generated after frame is assembled after transmission data is generated in the upper layer.

[Event from Lower Layer] ◎ Carrier ON: Indicates that the physical layer signal control unit sensed the medium and changed from no carrier to present. ◎ Carrier off: Indicates that the medium has been carrier sensed by the physical layer signal control unit and changed from having carrier to having carrier.

[Internal Event] ○ Collision detection after completion of preamble transmission: After completion of preamble transmission, the medium is examined every time one bit of data is transmitted, and is generated when a collision occurs. ◎ Transmission completed: Generated when frame transmission is completed. ◎ Jam transmission completed: Generated when the transmission of jam bit string is completed.

Excessive collision at the completion of jam transmission: The trial counter reaches the maximum number of trials within the limit and is generated when the transmission of the jam bit string is completed. ◎ Delay timeout: Generated when the interframe spacing delay timer times out. ○ Backoff timeout: Generated when the backoff timer times out.

* Description of state value ◎ START: A state where initialization is not completed. ◎ IDLE: The state where there is no transmission frame, the medium is empty, and data transmission is not stopped. ◎ Transmit (TRANSMIT): A state in which a bit string of data is being sent. ◎ Jam: A state in which a jam bit string is being sent.

○ BACK OFF: Waiting for resending after collision, the medium is free. ○ BACK OFF DEFER: The media is busy waiting to be retransmitted after a collision. ○ BACK OFF DELAY: Waiting for retransmission after collision and waiting for interframe spacing.

◎ Busy postponement without sending request (DEFER NO
WAIT): The media is busy with no transmission frame. ◎ Busy postponement with transmission request (DEFER WAIT): The transmission frame is held and the medium is busy. ◎ Delay without transmission request (DELAY NO WAIT): A state where there is no transmission frame and inter-frame spacing is in progress. ◎ Delay with transmission request (DELAY WAIT): A state where there is a transmission frame and inter-frame spacing is in progress.

* Description of operation ◎ Initialization execution: Stop all timers, reset all internal variables, and wait for carrier off. ○ Transmission start: Starts transmission of the preamble bit string and the data bit string. ◎ Start transmission of preamble: Start transmission of preamble bit string. ◎ Start data transmission: Starts transmitting the data bit string after the preamble.

◎ Jam transmission start: Transmission of a jam bit string is started. ◎ Successful transmission display: Notifies that the frame has been successfully transmitted. ◎ Transmission failure display: Notifies that the frame transmission failed.

Trial counter addition: The trial number of the same frame is added to the recorded counter. ◎ Trial counter reset: The counter recording the number of trials of the same frame is initialized to 0. ○ Start backoff timer: Calculate the delay time according to the binary exponential backoff algorithm and set the backoff timer to that value.

○ Stop the back-off timer: Stop the back-off timer. ◎ Delay timer start: Calculates the delay time for random interframe spacing and sets the delay timer to that value. ◎ Delay timer stop: Stop the delay timer.

[0049]

As is clear from the comparison between the above description of the contents of Tables 1 and 2 and the descriptions of the contents of Tables 3 and 4, the conventional retransmission limited CSMA / CD is known.
In the media access control device for the system, the connection interface with the transmission path signal control device is realized by the control logic in the media access control device as described above. In this case, CSMA / CD without the conventional retransmission restrictions
It is necessary to incorporate into the media access control device a function that allows the collision detection function, which was not required in the system, to be always accepted as an asynchronous event.

By the way, according to the IEEE 802.3 standard, collision detection is performed only during transmission processing, and moreover, a mechanism for synchronously detecting a collision detection indication from the transmission path signal control unit every time 1 bit transmission of the transmission signal is completed. ing. Therefore, in the media access control device that executes the retransmission limited CSMA / CD system, the degree of modification from the conventional media access control device is large and the control logic itself becomes more complicated.
Software burden increases. This is a retransmission-restricted CSMA
This is because the transmission restriction processing of the non-collision related stations at the time of collision detection of the / CD method was realized by including it in the transmission state mechanism of media access control.

The present invention has been made in view of the above circumstances, and in a retransmission limiting type CSMA / CD multiplex transmission apparatus, collision detection by the media access control apparatus provided therein is not an asynchronous event. In the same manner as that of the conventional CSMA / CD method that does not perform retransmission restriction, the synchronous detection can be performed during the transmission process, and the configuration and equivalent control mechanism shown in Tables 1 and 2 are realized. , Conventional CSMA
It is an object of the present invention to provide a multiplex transmission device capable of simplifying the transmission state mechanism by reducing the degree of modification from the media access control device in the / CD method.

[0052]

A multiplex transmission apparatus according to the present invention is a transmission process in a media access control apparatus,
When another station is transmitting a signal, that is, when the carrier signal (CARRIER) from the transmission path signal control device is on (active), the transmission start is postponed even if the transmission signal is held. However, in the retransmission-restricted CSMA / CD method, in addition to the above case, it is necessary to delay the start of transmission even when a collision is detected in which the own station is not involved. Both the postponement of transmission of the conditions can be controlled using the carrier signal (CARRIER). Specifically, when a collision is detected on the transmission path that does not involve the own station, the existing signal line (signal line for carrier signal) is used until the successful transmission by another station on the transmission line is detected. A transmission limiting device including a mechanism for delaying transmission from the access control unit and a timer mechanism for monitoring deadlock is provided between the media access control device and the transmission path signal control device. There is.

Since the transmission restriction device is provided, the function related to the transmission restriction is excluded from the transmission state mechanism in the media access control device, and the collision detection is performed in the same manner as in the conventional CSMA / CD system which does not perform the transmission restriction. In addition, the software load is reduced by replacing with a transmission state mechanism that synchronously detects during signal transmission.

It should be noted that the transmission limiting device may be installed in the media access control device, installed in the transmission path signal control device, or independent.

[0055]

In the multiplex transmission apparatus according to the present invention, the transmission status mechanism in the media access control apparatus synchronously detects during signal transmission, but transmission limitation is not performed, and instead, another station is transmitting signal. That is, when the carrier signal (CARRIER) from the transmission path signal control device is ON (active), the transmission start is postponed by the transmission restriction device even if the transmission signal is held. Also, the transmission start is postponed by the transmission limiting device even when a collision is detected in which the own station is not involved.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the configuration of the main part of the multiplex transmission device according to the present invention. The other parts of the multiplex transmission apparatus of the present invention are the same as those of the conventional multiplex transmission apparatus shown in FIG.

The media access control device 23 provided in the multiplex transmission device according to the present invention is provided with a transmission limiting device 25 between it and the transmission path signal control device 22 as shown in the block diagram of FIG. In addition, the interface between the media access control device 23 and the transmission path signal control device 22 is also configured as shown in the block diagram of FIG.

The medium access control device 23 delays the start of transmission even when the other station is transmitting a signal, that is, when the carrier signal (CARRIER) from the transmission path signal control device 22 is on, even if the transmission signal is held. . In addition, in the retransmission-restricted CSMA / CD system, it is necessary to postpone the start of transmission when a collision is detected in which the own station is not involved, other than the above case. Therefore, in the media access control transmission processing by the media access control device provided in the multiplex transmission device of the present invention,
In both cases, the carrier signal (C
ARRIER) is used to control other channels on the transmission line 1 by using the existing signal line (signal line for carrier signal) when detecting a collision on the transmission line 1 not involving the own station. A transmission limiting circuit 25 is a mechanism for delaying the transmission from the media access control unit until the successful transmission by the station is detected.
2 and a transmission limiting device 25 having an internal timer 251 as a timer mechanism for monitoring deadlock and the like are provided between the media access control device 23 and the transmission path signal control device 22.

From the transmission path signal control device 22 to the media access control device 23, CARRIER (carrier signal), RCV-CLOCK
(Reception data synchronization clock), RCV-DATA (reception data serial line), COLLISION (collision detection signal), TRN-CLOCK (transmission data synchronization clock) are sent respectively, and the media access control device 23 controls the transmission line signal. TRN to device 22
-DATA (transmission data serial line) and TRN-ENEBLE (transmission permission signal) are sent respectively.

The CARRIER was directly input from the transmission path signal control device 22 to the media access control device 23 in the conventional device, but in the media access control device 23 provided in the multiplex transmission device of the present invention, CARRIER (I) output from the transmission path signal control device 22 is input to the transmission limiting device 25. Then, from the transmission limiting device 25, CARRIER
(O) is output, and this is input to the media access control device 23.

RCV-CLOCK is a rectangular wave signal output from the transmission path signal control device 22 to the media access control device 23, and the transmission path signal control device 22 receives data (bit string).
Is used as a bit synchronization signal when being transmitted to the media access control device 23.

RCV-DATA is received data output from the transmission path signal control device 22 to the media access control device 23 as a bit string, and is synchronized with RCV-CLOCK described above. CARR
IER (I) is turned on (active) when there is a signal on the transmission line 1 and is transmitted from the transmission line signal control device 22 to the transmission limiting device.
Output to 25. Further, CARRIER (O) is output from the transmission limiting device 25 and input to the media access control device 23. If this is on (active), a transmission delay instruction and a reception start instruction to the media access control device 23 are issued. means.

COLLISION is turned on (active) when a collision is detected on the transmission line 1, and is output from the transmission line signal control device 22 to the media access control device 23.
TRN-CLOCK is a rectangular wave signal that is always output from the transmission path signal control device 22 to the media access control device 23, and is used as a bit synchronization signal when sending transmission data (bit string) from the media access control device 23. To be done.

TRN-DATA is a media access control device 23.
The transmission data is transmitted from the transmission path signal control device 22 as a bit string, and is synchronized with the above-mentioned TRN-CLOCK. TRN-
ENABLE is data transmitted from the media access control device 23.
Transmission of (bit string)
It is turned on (active) to notify 22 and is output from the media access control device 23 to the transmission path signal control device 22 during transmission of the above-mentioned transmission data (TRN-DATA).

Further, in the media access control device 23, a control logic is incorporated based on the transmission state mechanism as shown in Table 5. Specifically, the control logic of this media access control device 23 excludes the processing related to transmission restriction from the transmission state mechanism in the media access control device in the case of the conventional retransmission restriction type CSMA / CD system, and conventionally detects collision detection. Similar to the CSMA / CD type, it is replaced with a transmission state mechanism that detects synchronously during signal transmission.

[0066]

[Table 5]

The contents of Table 5 are as follows. * Description of event [Event from management unit] ○ Initialization: Generated by the management unit to enable the transmission media access control unit.

[Event from Upper Layer] Data Request: Generated after frame is assembled after transmission data is generated in the upper layer.

[Event from Lower Layer] ○ Carrier-on: Indicates that the physical layer signal control unit senses the medium and changes from no carrier to present. ○ Carrier off: Indicates that the media is carrier sensed by the physical layer signal control unit and changes from the presence of carrier to the absence of carrier. [Internal event]

Collision detection after completion of preamble transmission: After completion of preamble transmission, the medium is checked every time one bit of data is transmitted, and a collision is generated. ○ Transmission completed: Generated when the frame transmission is completed. ○ Jam transmission completed: Generated when the transmission of the jam bit string is completed.

Excessive collision at the completion of jam transmission: The trial counter reaches the maximum number of trials within the limit, and is generated when the transmission of the jam bit string is completed. ○ Delay timeout: Generated when the interframe spacing delay timer times out. ○ Backoff timeout: Generated when the backoff timer times out.

* Description of status values ○ START: Status where initialization is not completed. ○ Idle: A state where there is no transmission frame, the medium is empty, and data transmission is not stopped. ○ TRANSMIT: A data bit string is being sent.

Jam: A state in which a jam bit string is being sent. ○ Busy postponed without request for transmission (DEFER NO WAIT): The medium is busy without transmission frame. ○ Busy postponed with transmission request (DEFER WAIT): The transmission frame is held and the medium is busy.

Delay without requesting transmission (DELAY NO WAI
T): A state in which inter-frame spacing is in progress without a transmission frame. ○ Delay with transmission request (DELAY WAIT): A state where there is a transmission frame and inter-frame spacing is in progress.

* Description of operation ○ Initialization execution: Stop all timers, reset all internal variables, and wait for carrier off. ○ Transmission start: Starts transmission of the preamble bit string and the data bit string. ○ Preamble transmission start: Starts transmission of the preamble bit string.

Start of data transmission: Start transmission of the data bit string after the preamble. ○ Jam transmission start: Starts sending jam bit strings. ○ Successful transmission display: Notifies that the frame has been successfully transmitted.

Display of transmission failure: Notifies that transmission of a frame has failed. ○ Trial counter addition: Adds to the counter that records the number of trials of the same frame.

Trial counter reset: The counter recording the number of trials of the same frame is initialized to 0. ○ Delay timer start: Calculate the delay time of random inter-frame spacing and set the delay timer to that value. ○ Delay timer stop: Stop the delay timer.

The transmission status mechanism by the media access control device provided in the multiplex transmission apparatus of the present invention shown in Table 5 is shown in Table 3 and Table 4 of the conventional CS.
Compared with the transmission state mechanism of the media access control of MA / CD method, "backoff timeout", "backoff", "backoff busy postponement", "backoff delay", "backoff timer start", "backoff" 6 items of "Stop timer" have been reduced, and there is no new item added.

That is, as a matter of course, comparing with the conventional retransmission limited CSMA / CD system shown in Tables 1 and 2, Table 3
Also, as compared with the conventional CSMA / CD system shown in Table 4, it is clear that the transmission state mechanism of the media access control device provided in the present invention has a small software load.

Next, the operation of the multiplex transmission apparatus of the present invention will be described with reference to the timing chart of FIG. 2 when the transmission restriction is released from the transmission restricted state.

The transmission limiting circuit 252 in the transmission limiting device 25 is
When it is detected that a collision that does not involve itself is occurring on the transmission path 1, that is, the TRN-ENABLE signal from the media access control device 23 is in the off state as shown in Fig. 2 (d). As shown in FIG. 2 (b), while the CARRIER (I) from the transmission line signal controller 22 is in the ON state, as shown in FIG. 2 (c), COLLISION is set even once. When it is turned on, CA from the transmission line signal control device 22
CARRIER (O) to the media access control device 23 is turned off once at the timing when RRIER (I) is turned off next.

Then, the media access control device 25
Within the delay time until the transmission media access control device 23 starts the transmission process, the media access control device 23
By turning on CARRIER (O) of, the transmission is limited after detecting a collision in which the own station is not involved.

Here, the reason why CARRIER (O) given from the transmission limiting circuit 252 to the media access control device 23 is once turned off is that turning on / off of CARRIER (0) is a reception process for the media access control device 23. This is because it also has the meaning of a start / end instruction, and is for notifying the media access control device 23 of the trigger for discarding the fragmented frame due to the collision received while CARRIER (O) is in the ON state.

The transmission is restricted in this way, and during this transmission restriction, that is, CARR from the transmission line signal control device 22 is set.
IER (I) is off, media access controller 23
If the signal transmission by another station is successful while CARRIER (O) to the ON state is on, that is, from the transmission line signal control device 22.
CARRIER (I) is turned on again and then COLLISION
If CARRIER (I) is turned off without the signal being turned on, the transmission limit circuit will be activated at that timing.
252 is CARR output to the media access control device 23
IER (O) is also turned off and the transmission restriction is released.

In addition to the above, the deadlock time-out as shown in the timing chart of FIG. 3 may be the timing for releasing the transmission restriction. CA to the media access control device 23 first because of transmission restrictions
When the RRIER (O) is turned on, the internal timer 251 of the transmission limiting device 25 is activated at the timing shown in FIG. 2, so that all stations connected to the transmission path 1 are set to the transmission limiting state. You will be provided with a means of recovery if you fall. That is,
The internal timer 251 of the transmission limiting device 25 is started at the above-mentioned timing, enters the deadlock monitoring state, and stops when the signal transmission of another station starts. However, every station connected to transmission line 1 has a fixed time (deadlock monitoring time)
If the internal timer 251 in the transmission limiting device 25 times out without transmitting a signal within the time period shown in FIG.
As shown in (3), the transmission restriction device 25 turns off CARRIER (O) to the media access control device 23 to release the transmission restriction.

Next, the case where a collision is detected during transmission as shown in the timing chart of FIG. 4 will be described. When the local station detects a collision during signal transmission, the transmission limiting circuit 252 does not operate the CARRIER (O) output to the media access control device 23, and the transmission line signal control device
CARRIER (I) from 22 is passed through as it is and input to the media access control device 23. That is, as shown in FIG. 4 (d), the TRN-EN from the media access control device 23
If the COLLISION is turned on as shown in FIG. 4 (c) while the EBLE is turned on, the transmission restriction circuit 252 keeps the CARR from the media access control device 23 thereafter.
Media access control device through IER (I)
Sending is not restricted by giving it as CARRIER (O) to 23.

The transmission limiting device 25 may be installed in the media access control device 23, the transmission path signal control device 22, or an independent device as shown in FIG. .

[0089]

As described above in detail, according to the multiplex transmission apparatus of the present invention, the conventional retransmission limitation is performed without the collision detection as an asynchronous event in the medium access control of the retransmission limitation type CSMA / CD method. Since it is possible to detect synchronously during the transmission process like the non-existent CSMA / CD method, the media access control device is less modified from the conventional CSMA / CD method and the transmission state mechanism is simplified. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a multiplex transmission device according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the multiplex transmission device of the present invention.

FIG. 3 is a timing chart for explaining the operation of the multiplex transmission device of the present invention.

FIG. 4 is a timing chart for explaining the operation of the multiplex transmission device of the present invention.

[Fig. 5] Communication device using conventional general CSMA / CD
It is a block diagram showing a configuration of (station).

FIG. 6 is a block diagram showing an interface between a media access control device and a transmission line signal control device of a communication device adopting a conventional general CSMA / CD.

[Explanation of symbols]

 22 Transmission line signal control device 23 Media access control device 25 Transmission limiting device 252 Transmission limiting circuit

Claims (1)

[Claims] 1. When a plurality of stations connected to a transmission line transmit a signal, when the transmission line is free, the signal is transmitted immediately, and when the transmission line is being used by another station, the transmission is successful. Media access control, which waits until completion and when there is a collision with other stations at the same time, the stations not involved in the collision stop signaling until the next successful transmission by the other station is completed. In a multiplex transmission device equipped with a device, means for detecting that another station is transmitting a signal and that a collision has occurred due to signal transmission between other stations, and other means depending on the detection result of the means. A multiplex transmission device comprising: a transmission limiting device having means for stopping the signal transmission to the media access control device while the station is transmitting a signal and after detecting a collision between other stations.