JPH04364626A - Private communication equipment - Google Patents

Abstract

PURPOSE:To prevent violation against rules by suitably preventing it that a data whose length is less than the specified length is sent to a LAN transmission line. CONSTITUTION:A collision detection circuit 5 sets an output of a D-FF 6 to an H level when two outputs or more of carrier sense circuits 1-3 reach an H level. Then when all outputs of the carrier sense circuits 1-3 reach an L level, an OR gate 4 is used to reset an output of the D-FF 6 to an L level. A reset pulse generator 8 outputs a reset pulse of a first come priority circuit 10 synchronously with the falling of the output of the OR gate 4 to reset the first come priority circuit 10. Moreover, a collision data generated by a collision data generator 9 is sent to collision display lines C1-C3 while an output of the D-FF 6 is at an H level.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides data output from each of a plurality of connected terminals to a CSMA/CD (CSMA/CD).
carrier sense multiple a
ccess/collision detection
) method for transmitting data to a local area network (LAN).

0002

2. Description of the Related Art First, collision monitoring control in a conventional local area communication device (so-called multi-port transceiver) will be explained with reference to FIG.

First, terminal A connects transceiver cable L1
When data is sent to a multi-port transceiver (hereinafter referred to as a transceiver) D via a transmission line S1 within the LAN, the transceiver D sends the data to a LAN transmission line. Transceiver D also receives data sent via transmission line S1,
Receiving line R1 in transceiver cables L1, L2, L3
, R2, and R3 to terminals A, B, and C, respectively.

[0004] Terminals B and C, which are not outputting data, cannot output data because the other terminals are transmitting data when data is being sent back via the receiving lines R2 and R3. Do not do this. If terminals B and C have data to transmit, they transmit the data after terminal A has finished transmitting and data is no longer returned via receiving lines R2 and R3. Therefore, the system is normally in a state where two or more terminals transmit data at the same time, that is, no collision occurs.

By the way, for example, it takes some time (for example, 0.5 μs) for data sent from terminal A to reach terminals B and C via transceiver D. Each of the terminals A to C detects whether or not data is being transmitted via the receiving lines R1 to R3, but this detection requires some time (for example, 1 μs) after the data arrives. That is, it takes some time (for example, 1.5 μs) after terminal A starts transmitting data until terminals B and C learn that terminal A is transmitting data. Therefore, terminals B and C recognize this period as a period in which they can send data, and if they start sending data, a collision will occur.

[0006] Transceiver D has a first-come, first-served priority circuit that selects the data of the terminal that is transmitting the data that arrived first, and blocks the data of other terminals, so it is not destroyed. Data is never sent to the LAN transmission line. In addition, we monitor the occurrence of collisions, and if a collision occurs as described above, the transceiver cable
1, L2, and L3 through collision display lines C1, C2, and C3, each terminal A to C is configured to stop sending data, and is capable of resolving the collision. It becomes.

However, in a LAN, it is specified that data of at least a specified length (for example, 96 bits) is to be transmitted continuously, and each terminal A to C does not finish outputting the specified length even after receiving the conflicting data. Data will continue to be output until At this time, the data output of the terminal that started data output first ends first. When the data output from one terminal is completed in this manner, the transceiver 5 determines that the collision has been resolved, stops transmitting the collision data, and resets the first-come, first-served priority circuit to prepare for subsequent data transmission. However, at this time, since the terminal that started data output later is still outputting data, the first-come-first-served priority circuit selects this data and sends it out to the LAN transmission line. Here, the amount of data output by the terminal that started data output later is the same amount as the terminal that started data output first, so the remaining amount of data output by the terminal that started data output later is
This is the amount of data corresponding to the difference in output start time. In other words, data whose amount is less than the specified length will be sent to the LAN transmission path.

[0008]

[Problem to be Solved by the Invention] As described above, in conventional local communication equipment, since two terminals outputting data at the same time is regarded as a collision, the problem occurs when one terminal finishes outputting data. There was a problem in that data that was less than the specified length was sent to the LAN transmission line, violating the regulations.

[0009] The present invention has been made in consideration of such circumstances, and its purpose is to appropriately prevent data shorter than a specified length from being sent to a LAN transmission line, The purpose of the present invention is to provide a local communication device that can prevent violations of regulations.

0010

[Means for Solving the Problems] A first invention provides a data input detection means, such as a carrier sense circuit, which is provided corresponding to each of a plurality of communication terminals and detects the presence or absence of data output from the corresponding communication terminal. a collision detection means, such as a collision detection circuit, which detects the occurrence of a collision based on the detection results of each of the output detection means; and a collision detection means of the plurality of communication terminals based on the detection results of each of the data input detection means. and non-output detection means such as an OR gate for detecting that all of the communication terminals have not output data, and after the collision detection means detects a collision, the non-output detection means detects that all of the plurality of communication terminals have not output data. In response to the detection that data has not been output yet, only the output data of the first one of the plurality of communication terminals to output data is sent to the local area network until a reset is performed. For example, a first-come-first-served priority circuit or other first-come-first-served data selection means is reset to select a first-come-first-served basis and block output data from other communication terminals.

[0011] In addition to the first invention, a second invention is characterized in that after the collision is detected by the collision detection means, the non-output detection means detects that all of the plurality of communication terminals are not outputting data. Until the collision is detected, predetermined information such as collision data is provided to the plurality of communication terminals to notify that a collision is occurring.

0012

[Operation] According to the first invention, until a reset is performed, only the output data of the first one of the plurality of communication terminals to output data is selected as the data to be sent to the local area network, and the other For example, after the first-arrival data selection means such as the first-come-first-served priority circuit is reset, and the collision detection means detects a collision, the output data of all the communication terminals are cut off by the non-output detection means. This is done in response to detection that no output has been made.

Therefore, regardless of the period during which the collision actually occurs, the first-arrival data selection means is reset after all data output from the terminal that was outputting data at the time of the collision is completed, and the first-arrival data selection means is reset. The device enters standby mode.

According to the second aspect of the present invention, after the collision is detected by the collision detection means, until the non-output detection means detects that all of the plurality of communication terminals are not outputting data. During this time, predetermined information such as collision data is provided to the plurality of communication terminals to notify that a collision is occurring. Therefore, even when a collision is not actually occurring, as long as the terminal that was outputting data at the time of the collision continues to output data, it is treated as a collision.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a local area communication device (multiport transceiver) according to this embodiment. Here, as shown in FIG. 3, a transceiver to which three terminals A to C are connected is illustrated, and the connection state between the transceiver, the terminals, and the LAN transmission path is similar to that in FIG. 3.

In the figure, 1, 2, and 3 are carrier sense circuits. These carrier sense circuits 1 to 3 include transmission lines S1 to
Whether or not data has arrived is detected via S3. The carrier sense circuits 1 to 3 output an H level when detecting the arrival of data. The outputs of carrier sense circuits 1 to 3 are input to OR gate 4 and collision detection circuit 5.

Collision detection circuit 5 includes carrier sense circuit 1
Based on the detection results of steps 3 to 3, the occurrence of a collision is detected. The collision detection circuit 5 outputs an H level when a collision is detected.

6 is a D-flip-flop circuit (hereinafter referred to as D
-FF). The H level is connected to the data input terminal of this D-FF6. Further, the output of the collision detection circuit 5 is input to the clock terminal, and the output of the OR gate 4 is input to the reset terminal. And D-
The output of FF6 is input to one input terminal of AND gate 7.

The output of the collision data generator 9 is input to the other input terminal of the AND gate 7. The collision data generator 9 outputs a predetermined pattern of collision data,
The AND gate 7 turns on/off the output of the collision data output from the collision data generator 9 according to the output of the D-FF 6.
Turn off. The output of the AND gate 7 is the collision display line C1~
Sent to C3.

The reset pulse generator 8 is connected to the OR gate 4
A predetermined reset pulse is generated in synchronization with the fall of the output. The output of the reset pulse generator 8 is input to a first-come, first-served priority circuit 10.

The first-come-first-served priority circuit 10 selects the transmission line S1 to S3 on which data arrives first, and supplies only the data transmitted via the selected transmission line to the data transmission section 11. , to the receiving lines R1 to R3. Note that data transmitted via other transmission lines will be blocked. The first-come-first-served priority circuit 10 uses a reset pulse generated by the reset pulse generator 8 to reset the operation from the state in which one of the transmission lines S1 to S3 is selected to the state in which it waits for the first-come-first-served line. The data sending unit 11 is
The data output from the first-come, first-served priority circuit 10 is sent to the LAN transmission line. Next, the operation of the transceiver configured as above will be explained with reference to the time chart shown in FIG.

First, when terminal A starts outputting data (at time T1 in FIG. 2) and data arrives via transmission line S1, first-come-first-served priority circuit 10 selects transmission line S1 and The data transmitted via the data transmitter 11 is given to the data transmitter 11. As a result, the data output from terminal A is sent from the data sending section 11 to the LAN transmission path.

Further, at time T1, the output from the carrier sense circuit 1 becomes H level. When the output of the carrier sense circuit 1 becomes H level in this way, the output of the OR gate 4 also becomes H level. Although one input of the collision detection circuit 5 also becomes H level, the collision detection circuit 5 detects the occurrence of a collision when two or more inputs become H level, and its output does not change. .

In this state, after terminal A starts sending data and before terminals B and C can know that terminal A is sending data (time T2 in FIG. 2), terminal When B starts outputting data, the output of the carrier sense circuit 2 becomes H level. As a result, the two inputs of the collision detection circuit 5 become H level, so the collision detection circuit 5 recognizes that a collision has occurred and outputs an H level. When the output of the collision detection circuit 5 becomes H level, the output of the D-FF 6 also becomes H level. As a result, the AND gate 7 is opened, the collision data generated from the collision data generator 9 is sent to the collision display lines C1 to C3, and the terminals A to C are notified of the occurrence of a collision. Note that the first-come-first-served priority circuit 10 continues to select the transmission line S1, and data arriving via the transmission line S2 is blocked. In other words, the data output from terminal A continues to be sent to the LAN transmission path.

[0025] Terminal A and terminal B have collision display lines C1 to
It is informed that a collision has occurred based on the collision data transmitted via C3, and data output is stopped after the specified length of transmission is completed. Since terminal A has started outputting data first, terminal A stops outputting data first (Figure 2
(T3 time point in the middle). As a result, the output of the carrier sense circuit 1 becomes L level. When the output of the carrier sense circuit 1 becomes L level, only one input of the collision detection circuit 5 becomes H level, so that the output becomes L level. but,
The output of OR gate 4 remains at H level, and D-FF
The input to the reset terminal No. 6 remains at H level. Therefore, the output of the D-FF6 is maintained at the H level, and the collision data continues to be sent to the collision display lines C1 to C3. Furthermore, since the reset pulse generator 8 generates a reset pulse in synchronization with the fall of the output of the OR gate 4, it does not generate a reset pulse at this time point T3. Therefore, the first-come-first-served priority circuit 10 continues to select the transmission line S1 even though the data output of the terminal A has stopped.

When terminal B stops outputting data (at time T4 in FIG. 2), the output of carrier sense circuit 2 becomes L level. All inputs of the OR gate 4 become L level, and its output becomes L level. As a result, D-
FF6 is reset and the output becomes L level. D-F
When the output of F6 becomes L level, AND gate 7 is closed and sending of collision data to collision display lines C1 to C3 is stopped. Further, the reset pulse generator 8 generates a reset pulse P by capturing the fall of the output of the OR gate 4. The first-come-first-served priority circuit 10 is reset by this reset pulse P, ends the selection of the transmission line S1, and enters a first-come-first-served standby state.

[0027] Here, terminal A comes first, then terminal B
Although the explanation has been given using the case where the terminal starts outputting data later, the same operation applies regardless of the terminal that starts outputting data first and the terminal that starts outputting data later. Further, the same operation occurs even in the event of a collision in which all three terminals A to C output data.

As described above, according to this embodiment, when a collision occurs, all data outputs from terminals A to C are stopped until the outputs of carrier sense circuits 1 to 3 are all at L level, that is, all data outputs from terminals A to C are stopped. First-come-first-served priority circuit 10 until the status is reached.
is not reset, and the first-come, first-served priority circuit 10 maintains a state in which the transmission line corresponding to the terminal that first started data output is selected. And each carrier sense circuit 1 to 3
The first-come-first-served priority circuit 10 is reset when all the outputs of the terminals become L level, that is, when all the data outputs of the terminals A to C are stopped.

[0029] Thus, data output from a terminal that later starts data output is completely blocked and is not sent to the LAN transmission path. Therefore, data less than the specified length will not be sent to the LAN transmission path.

Furthermore, between the time T3 when the data output of terminal A ends and the time T4 when the data output of terminal B ends, the first-come-first-served priority circuit 10 Since terminal A has selected the output data of terminal A, there is no data to be returned to terminals A to C during this period. Therefore, terminal C cannot know that terminal B is outputting data, and there is a risk that a collision will occur again. Since data is being sent, this collision data allows terminal C to recognize that a collision is occurring, and prevents another collision from occurring.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, a transceiver to which three terminals are connected is illustrated, but the present invention can be applied to any transceiver to which two or more terminals are connected.

Furthermore, in the above embodiment, after a collision occurs, the collision data is transmitted until the data output of all terminals is stopped, but the period for transmitting the collision data is the same as before. It is also possible to do this only during the period in which this is occurring. This is because even if the terminal that started data output later continues to output data, the first-come, first-served priority circuit selects the terminal that started outputting data first, so another terminal starts outputting data. This is because even if a collision occurs after starting the process, it is possible to prevent data shorter than the specified length from being output to the LAN transmission path. However, the efficiency decreases because the terminal that last started data output cannot perform a normal data transmission operation until it outputs data of the specified length, so the configuration shown in the above embodiment cannot be used. preferable. In addition, various modifications can be made without departing from the gist of the present invention.

[0033]

Effects of the Invention The first invention provides data input detection means, such as a carrier sense circuit, which is provided corresponding to each of a plurality of communication terminals and detects the presence or absence of data output of the corresponding communication terminal, and Collision detection means such as a collision detection circuit detects the occurrence of a collision based on the respective detection results of the detection means, and all of the plurality of communication terminals detect the occurrence of data based on the detection results of the data input detection means. and a non-output detection means such as an OR gate for detecting an output, and after the collision detection means detects a collision, the non-output detection means detects that all of the plurality of communication terminals have not output data. In response to the detection, until a reset is performed, only the output data of the first one of the plurality of communication terminals to output data is selected as the data to be sent to the local area network; For example, first-come-first-served data selection means such as a first-come first-served priority circuit is reset to block output data from other communication terminals.

[0034] In addition to the first invention, a second invention is characterized in that after the collision detection means detects a collision, the non-output detection means detects that all of the plurality of communication terminals are not outputting data. Until the collision is detected, predetermined information such as collision data is provided to the plurality of communication terminals to notify that a collision is occurring. These provide a local communication device that can accurately prevent data that is less than the specified length from being sent to the LAN transmission path and prevent violations of the regulations.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a local area communication device (multi-port transceiver) according to an embodiment of the present invention.

FIG. 2 is a time chart showing the operation timing of each part in FIG. 1;

FIG. 3 is a diagram explaining the prior art.

[Explanation of symbols]

1, 2, 3...Carrier sense circuit, 4...OR gate, 5
...Collision detection circuit, 6...D flip-flop (D-FF)
, 7...AND gate, 8...Reset pulse generator, 9...
Collision data generator, 10... First-come-first-served priority circuit, 11... Data sending section, S1, S2, S3... Transmission line, R1, R2, R3
...Reception line, C1, C2, C3...Collision display line.

Claims (2)

[Claims] Claim 1: A local area communication device that sends data output from a plurality of connected communication terminals to a local area network, and until a reset is performed, data is output to the first of the plurality of communication terminals. a first-arrival data selection means that selects only the output data of one communication terminal as the data to be sent to the local area network and blocks the output data of other communication terminals, the first-arrival data selection means is provided corresponding to each of the plurality of communication terminals; data input detection means for detecting the presence or absence of data input and output from a corresponding communication terminal; collision detection means for detecting the occurrence of a collision based on the respective detection results of the data input detection means; Non-input detection means detects that all of the plurality of communication terminals have not outputted data and there is no data input based on the detection results of each of the input detection means, and a collision is detected by the collision detection means. and a reset means for resetting the first-arrival data selection means in response to the fact that the non-input detection means detects that no data has been inputted. [Claim 2] After the collision is detected by the collision detection means, until the non-output detection means detects that all of the plurality of communication terminals have not outputted data, the information indicating that a collision is occurring is detected. 2. The local area communication device according to claim 1, further comprising collision notification means for providing predetermined information to the plurality of communication terminals to notify the plurality of communication terminals.