JPH053478A - Multiplex communication controller - Google Patents

Abstract

(57) [Abstract] [Purpose] The circuit scale can be reduced, the transmission speed can be improved easily, and there is determinism of the communication end time, and a fixed time can be guaranteed. ,
A multiplex communication control device is provided. The transmission control circuit 18 can start transmission unless the carrier sense detection circuit 3 detects carrier sense, and if there is carrier sense, transmission can be performed until the idle detection circuit 15 detects idle. If it cannot, and if it collides, it outputs a dominant signal ("1"), then stops transmission, and cannot re-transmit until idle is detected.
A configuration in which a plurality of multiplex communication control circuits 23, which are configured to start reception when M is detected, are connected to the multiplex communication bus 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to so-called CSMA /
CD (Carrier Sense Multiple Access / Collision De)
tection: Carrier detection multiple access / collision detection) The present invention relates to a multiplex communication control device using a transmission method.

[0002]

2. Description of the Related Art A conventional CSMA / CD type multiplex communication control device is, for example, "" Theory of Information Network ".
Iwanami Course Information Science-5 ”.

FIG. 7 is a block diagram showing the overall configuration of the conventional device as described above. In FIG. 7, reference numeral 1 denotes a multiplex communication bus, and a plurality of multiplex communication control circuits 22 are connected to the multiplex communication bus 1 to form a multiplex communication control device. Further, FIG. 3B is a diagram showing a communication format of a communication signal in the above-mentioned multiplex communication apparatus. The SD signal appears at the beginning of the communication signal and indicates the start of communication, EOM (En
The d of Message) signal is a signal indicating the end of the message.

FIG. 8 is a block diagram showing the configuration of the multiplex communication control circuit 22 described above. This multiplex communication control device
This is a general win-win CSMA / CD multiplex control device. In the multiplex communication control circuit 22 shown in FIG. 8, the bus interface circuit 6, which is generally called a physical layer, converts the state of the multiplex communication bus 1 and communication signals from the other into a reception signal 14 and outputs the received signal 14. 1 is converted into a communication signal and output to the multiplex communication bus 1. In addition, the idle detection circuit 2 receives the received signal 1
4 is an idle (a state in which there is no communication signal on the multiplex communication bus) for a certain fixed time from IMS (Inter Message)
Separation), and outputs the idle signal 9 to the transmission control circuit 8. Further, the carrier sense detection circuit 3 detects carrier sense (a state in which a communication signal exists on the multiplex communication bus) from the received signal 14, and the carrier sense signal 1
0 is output to the transmission control circuit 8. And the transmission control circuit 8
When the idle signal 9 is input and the carrier sense signal 10 is not input, the transmission signal 13 can be output to the bus interface circuit 6 at any timing and transmitted as a communication signal onto the multiplex communication bus 1. You can start doing.

Further, the collision detection circuit 5 compares the communication signal transmitted by the transmission control circuit 8 on the multiplex communication bus 1 with the communication signal received from the multiplex communication bus 1 to compare the multiplex communication bus 1 on the multiplex communication bus 1. Detects collision of communication signals. The collision detection circuit 5 collides with the communication signal on the multiplex communication bus 1 while the transmission control circuit 8 is transmitting the arbitration signal of the communication signal shown in FIG. 3B as the transmission signal 13 as described above. When the collision detection circuit 5 detects that (the player has lost due to a collision according to the priority order), the collision detection circuit 5 outputs a collision signal 11 to the transmission control circuit 8
Output to. When the collision signal 11 is given, the transmission control circuit 8 immediately stops the transmission. After that, when the idle detection circuit 3 detects the IMS, the transmission control circuit 8 can retransmit the communication signal to the multiplex communication bus 1. Further, after the idle detection circuit 2 detects the IMS, the SD detection circuit 4 detects an SD signal (a signal that appears at the beginning of the communication signal and indicates the start of communication), and the reception start signal 12 is received. The reception control circuit 7 receives the communication signal from the multiplex communication bus 1.

[0006]

However, in the conventional multiplex communication control device as described above, (1) when a transmission control circuit A in a certain multiplex communication control circuit A transmits a communication signal, another When the transmission control circuit B in the multiplex communication control circuit B transmits the communication signal at the same time and the transmission control circuit A loses the collision, the transmission control circuit A immediately stops the transmission and the transmission control circuit B The reception control circuit A in the multiplex communication control circuit A is configured to always receive the communication signal in order to survive the collision and continue to transmit the communication signal. Therefore, the reception control circuit A and the transmission control circuit A
Must operate completely independently and at the same time, the common part cannot be integrated into one circuit, and the transmission control circuit A and the reception control circuit A must be synchronized. Was complicated and large-scale.

(2) When a plurality of multiplex communication control circuits transmit communication signals at the same time, collision of communication signals occurs, and the most dominant communication signal remains. Therefore, the combined waveform that appears as a result of the collision of a plurality of communication signals needs to be established as a normal waveform on the multiplex communication bus 1. Therefore, the transmission delay of the communication signal depends on the electrical characteristics of the bus interface circuit 6. Is related to the condition for the waveform to be established, the limit of the transmission speed is decided,
There is a problem that it becomes an obstacle to the improvement of the transmission speed.

(3) When a certain multiplex communication control circuit transmits a communication signal and a collision occurs and loses the collision, the transmission control circuit 8 of the multiplex communication control circuit stops the transmission of the communication signal. After the idle detection circuit 2 detects the IMS, the transmission control circuit 8 retransmits the communication signal. However, at the time of this re-transmission, there is a possibility of colliding and losing, so it is not possible to predict when the transmission will end, and the communication of the multiplex communication control circuit that has transmitted the low-priority communication signal However, there is a problem in that the maximum time required for communication cannot be guaranteed as the multiplex communication control device.

The present invention has been made in order to solve the problems of the prior art as described above, the circuit scale can be reduced, the transmission speed can be easily improved, and the communication end time can be improved. It is an object of the present invention to provide a multiplex communication control device capable of guaranteeing a certain time with certainty.

[0010]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, in the present invention, when the idle detection circuit detects TGE which is idle for a certain fixed time and the carrier sense detection circuit does not detect carrier sense, the transmission control circuit transmits the communication signal at an arbitrary timing. You can start. In addition, when the collision detection circuit detects a collision of the communication signal on the multiplex communication bus while the transmission control circuit is transmitting the communication signal, the transmission control circuit may detect the collision of the multiplex communication bus on the multiplex communication bus for a certain period of time. After transmitting the communication signal in the dominant state (for example, “1”), the transmission is stopped. When the idle detection circuit detects TGn, which is smaller than the TGE and has a different length for each multiplex communication control circuit and is idle for a certain fixed time, the transmission control circuit causes the multiplex communication bus to operate. Retransmit communication signal up. If the transmission control circuit is not transmitting or retransmitting, the signal appears at the beginning of the communication signal and indicates the start of communication, and the same waveform as that on the multiplex communication bus does not exist other than the signal. A communication start signal detection circuit (corresponding to the SOM detection circuit 16 described later) that detects an SOM (Start of Message) signal, which is a signal, can always detect the SOM signal. When the circuit detects the SOM signal, it is reset from any state, and the reception control circuit can start receiving a communication signal from the multiplex communication bus.

[0011]

With the above-mentioned structure, in the present invention, when a communication signal collision occurs on the multiplex communication bus, there is no multiplex communication control circuit that survives the collision. When there is a collision of communication signals on the multiplex communication bus, all the multiplex communication control circuits that participated in the collision detect the collision and retransmit, and when retransmitting, participate in the collision. The multiplex communication control circuit that did not do so cannot start transmission until the multiplex communication control circuit that participated in the collision completes all retransmissions. Can be retransmitted without causing secondary collision of communication signals. Therefore, since the multiplex communication control circuit is in either the receiving state or the transmitting state and is not in the both states, the common portion of the transmitting control circuit and the receiving control circuit can be combined into one, and Since there is no need to synchronize the transmission control circuit and the reception control circuit, the circuit scale can be reduced. Further, when a collision occurs, it is not necessary to establish communication signals after that, so that the transmission rate can be easily improved. Also, since the maximum time required for communication is finite, the communication end time is deterministic, and a fixed time can be guaranteed.

[0012]

FIG. 1 is a block diagram of an embodiment of the present invention, in which a plurality of multiplex communication control circuits 2 are provided on a multiplex communication bus 1.
3 shows the overall configuration of the multiplex communication control device to which 3 is connected.

FIG. 2 is a block diagram of an embodiment of the multiplex communication control circuit 23. 2, the parts of the carrier sense detection circuit 3 for detecting carrier sense, the collision detection circuit 5 for detecting collision of communication signals, and the bus interface circuit 6 are the same as those in FIG. Also,
The idle detection circuit 15 detects an idle TGE for a certain period of time, outputs an idle signal 19, and
A retransmission start signal 20 is output by detecting a TGn that is smaller than the above TGE and has a different length for each multiplex communication control circuit and is idle for a certain fixed time.
The SOM detection circuit 16 is a characteristic signal among the communication signals, and the same waveform as that on the multiplex communication bus 1 does not exist other than that signal. SOM (Start
of Message) signal (see (a) of FIG. 3) is detected, and a reception start signal 12 is output. Also, the reception control circuit 17
The reception start signal 12 is input to control the reception of communication signals. In addition, the transmission control circuit 18 uses the carrier sense signal 1
0, a collision signal 11, an idle signal 19 and a retransmission start signal 20 are input to control the transmission of the communication signal 13.

Further, in this multiplex communication control device,
One of the multiplex communication control devices 23 is idle, in which all the multiplex communication control circuits 23 are not transmitting communication signals or all the multiplex communication control devices 23 are transmitting communication signals “0”. Has two states, active, which is the state in which it is transmitting the communication signal "1". Note that the communication signal “1” will be described as a dominant signal and the communication signal “0” will be described as a recessive signal. However, “0” will be a dominant signal and “1” will be a recessive signal. You can also

Next, the operation will be described. Multiplex communication control circuit 2
3, the bus interface circuit 6 converts the state and the communication signal on the multiplex communication bus 1 into a reception signal 14 and outputs it, and also converts the transmission signal 13 into a communication signal and outputs it onto the multiplex communication bus 1. Further, when the idle signal 19 is input from the idle detection circuit 15 and the carrier sense signal 10 is not input from the carrier sense detection circuit 3, the transmission control circuit 18 outputs the transmission signal 13 at any timing at any time. , And the transmission of the communication signal on the multiplex communication bus 1 can be started.
If the collision detection circuit 5 detects a collision of the communication signal on the multiplex communication bus 1 while the transmission control circuit 18 is transmitting the communication signal, the collision detection circuit 5 outputs the collision signal 11 to the transmission control circuit 18. To do.

When the transmission control circuit 18 receives the collision signal 11, the transmission control circuit 18 transmits the dominant state communication signal "1" on the multiplex communication bus 1 for a certain period (details will be described later), and then stops the transmission. When the idle detection circuit 15 detects the TGn and outputs the retransmission start signal 20 to the transmission control circuit 18, the transmission control circuit 18 can retransmit the communication signal onto the multiplex communication bus 1. Further, the transmission control circuit 18 outputs the reception prohibition signal 21 to the SOM detection circuit 16 when the transmission signal is being transmitted or is being retransmitted. If the reception prohibition signal 21 is not output, the SOM detection circuit 16
Detects the SOM signal and outputs the reception start signal 12 to the reception control circuit 17, whereby the reception control circuit 17 starts receiving the communication signal from the multiplex communication bus 1.

Next, FIG. 4 is a flow chart of the receiving operation,
FIG. 5 is a flowchart of the transmission operation. Further, Table 1 below is a table showing an example of the value of TGn when the multiplex communication control circuit 23 is eight (node 1 to node 8).

[0018]

[Table 1]

The outline of the operation at the time of transmission shown in FIG. 5 will be described below. (1) The multiplex communication control circuit 23 constantly monitors the multiplex communication bus 1 and, if there is no communication signal on the multiplex communication bus 1 (if the multiplex communication bus 1 is in an idle state), transmits the communication signal at an arbitrary timing. You can do it. (2) The multiplex communication control circuit 23, which has sent the communication signal even once from the idle state onto the multiplex communication bus, cannot perform transmission unless it detects the TGE. (3) The multiplex communication control circuit 23, which has started the transmission, unconditionally outputs the communication signal up to the arbitration signal of the communication format, and detects the collision during the transmission of the arbitration signal. (4) The multiplex communication control circuit 23 that has detected the collision outputs “1” until the period when the transmission of the arbitration signal ends, and stops transmitting the signals after the arbitration signal and ends the transmission of the communication signal. To do. Then, unless the TGn is detected, the retransmission cannot be performed.

Next, an outline of the operation at the time of reception shown in FIG. 4 will be described. (5) When the multiplex communication control circuit 23, which has once detected the SOM signal and started reception, again detects the SOM signal during reception, the reception state before that is ignored because a collision has occurred. , Reception starts again from the beginning.

As described above, when the multiplex communication control circuit 23 operates, the multiplex communication control circuit 23 is always in one of the receiving and transmitting states, and when a collision occurs, the subsequent communication signals are not transmitted. It is not necessary to be established, and the maximum time required for communication is finite, and a fixed time can be guaranteed.

Next, FIG. 6 shows four multiplex communication control circuits 2
3 (node 1 to node 4) is a diagram showing an example in which communication is performed, and Table 2 below is a table showing communication states of the multiplex communication control circuits 23 at that time. In addition, in FIG.
The communication states of the node 1, the node 2, the node 3, and the node 4 include the following states (1) to (4), and each node is in the state shown in Table 2. Send (single), receive (single), send (collision), receive (collision), send (retransmit), receive (rereceive).

[0023]

[Table 2]

Hereinafter, description will be made with reference to FIG. The waveform shown in FIG. 6 is the case where nodes 1, 2, and 3 simultaneously start transmission at the beginning of section A. In this case, node 1,
Each of 2 and 3 detects a collision during transmission of an arbitration signal and outputs a bit "1" for a certain period of time.
The other nodes 4, 5 and 6 are in a state in which they cannot transmit until carrier sense is detected and TGE is detected by the waveforms output from the nodes 1, 2 and 3. Next, all the nodes stop transmission, and TG1 (T corresponding to node 1
When the time of Gn) has elapsed, the node 1 becomes ready for transmission and starts transmission. The other nodes are in the transmission prohibited state (section B). Next, node 1 that has completed transmission
Will be in a transmission prohibited state until TGE is detected. Node 1 finishes the transmission, and TG2 (T corresponding to node 2
When the time of Gn) has elapsed, the node 2 becomes the transmission enabled state and starts transmission (section C). Similarly, in the section D, the node 3 transmits. Then, when the node 3 finishes the transmission, all the nodes are in the transmission prohibited state, and after that, when the TGE time has elapsed, all the nodes are in the transmission possible state. Moreover, the section E is a case where only one node transmits. In this case, the node 4 performs transmission, and when the TGE time elapses after the transmission is completed, all the nodes can transmit.

[0025]

As described above, in the present invention, the multiplex communication bus is constantly monitored, and the communication signal having two values, the dominant state and the recessive state, continuously exists on the multiplex communication bus. An idle detection circuit that measures the idle time in a non-existing state and detects an idle for a certain fixed time, and a carrier sense that is a change from a state without a communication signal on the multiplex communication bus to a state with a communication signal. Collision of communication signals on the multiplex communication bus by comparing the carrier sense detection circuit for detecting and the communication signal transmitted by the transmission control circuit on the multiplex communication bus with the communication signal received from the multiplex communication bus A collision detection circuit that detects the occurrence of a signal and a signal that appears at the beginning of a communication signal to indicate the start of communication, and that the same waveform as that on the multiplex communication bus does not exist other than that signal. Communication start signal detection circuit for detecting the communication start signal, the transmission control circuit for controlling the transmission of the communication signal on the multiplex communication bus, and the reception for controlling the reception of the communication signal on the multiplex communication bus In a multiplex communication control device in which a plurality of multiplex communication circuits composed of a control circuit and the multiplex communication circuit are connected to the multiplex communication bus, the multiplex communication control circuit is configured such that the idle detection circuit detects idle for a certain fixed time. And, if the carrier sense detection circuit does not detect the carrier sense, it is possible to start the transmission of the communication signal on the multiplex communication bus at any timing at any time, and during the transmission of the communication signal. When the collision detection circuit detects a collision of communication signals on the multiplex communication bus, it transmits a dominant state communication signal for a certain period of time on the multiplex communication bus. Then, after making the other multiplex communication control circuit detect the collision, the transmission is stopped, and the length is set to be smaller than the above idle for a certain period of time, and each multiplex communication control circuit has a different length. A transmission control circuit capable of retransmitting a communication signal onto the multiplex communication bus by detecting the idle for a certain period of time by the idle detection circuit, and the transmission control circuit must be transmitting or retransmitting the transmission signal. For example, the communication start signal detection circuit detects the communication start signal to start receiving the communication signal from the multiplex communication bus. Since the multiplex communication control circuit is in either the receiving state or the transmitting state and never in both states, it is possible to combine the common parts of the transmitting control circuit and the receiving control circuit into one. Moreover, it is not necessary to synchronize the receiver control circuit and the transmission control circuit, it is possible to reduce the scale of circuitry. (2) When a collision occurs, it is not necessary to establish communication signals after that, so that the transmission speed can be easily improved. (3) Since the maximum time required for communication is finite, the communication end time is deterministic, and a certain time can be guaranteed, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a multiplex communication control device of the present invention.

FIG. 2 is a block diagram of an embodiment of a multiplex communication control circuit in the multiplex communication control device of the present invention.

FIG. 3 is a diagram showing an example of a communication format.

FIG. 4 is a flowchart of a reception operation.

FIG. 5 is a flowchart of a transmission operation.

FIG. 6 is a waveform chart showing an example of a communication state.

FIG. 7 is a block diagram of an example of a conventional multiplex communication control device.

FIG. 8 is a block diagram of an example of a multiplex communication control circuit in a conventional multiplex communication control device.

[Explanation of symbols]

 1 ... Multiplex communication bus 2 ... Idle detection circuit 3 ... Carrier sense detection circuit 4 ... SD detection circuit 5 ... Collision detection circuit 6 ... Bus interface circuit 7 ... Reception control circuit 8 ... Transmission control circuit 9 ... Idle signal 10 ... Carrier sense signal 11 ... Collision signal 12 ... Reception start signal 13 ... Transmission signal 14 ... Reception signal 15 ... Idle detection circuit 16 ... SOM detection circuit 17 ... Reception control circuit 18 ... Transmission control circuit 19 ... Idle signal 20 ... Retransmission start signal 21 ... Reception Prohibition signal 22 ... Multiplex communication control circuit 23 ... Multiplex communication control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shizuhisa Watanabe 2520 Takaba, Katsuta-shi, Ibaraki Hitachi Ltd. Automotive Equipment Division (72) Inventor Kazumasa Sugiura 2520 Takata, Katsuta-shi, Ibaraki Stocks Company Hitachi Ltd. Automotive Equipment Division (72) Inventor Shigeru Oho 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd.

Claims (1)

Claim: What is claimed is: 1. An idle system in which a multiplex communication bus is constantly monitored and a communication signal having two values, a dominant state and a recessive state, is not continuously present on the multiplex communication bus. And a carrier sense detection for detecting a carrier sense which is a change from a state without a communication signal on the multiplex communication bus to a state with a communication signal on the multiplex communication bus. Collision detection for detecting a collision of a communication signal on the multiplex communication bus by comparing a communication signal transmitted from a transmission control circuit on the multiplex communication bus with a communication signal received from the multiplex communication bus A circuit and a signal that appears at the beginning of a communication signal and indicates the start of communication, and detects the communication start signal where the same waveform as that on the multiplex communication bus does not exist other than that signal. A communication start signal detection circuit for outputting, a transmission control circuit for controlling transmission of a communication signal on the multiplex communication bus, and a reception control circuit for controlling reception of a communication signal on the multiplex communication bus. In the multiplex communication control device in which a plurality of multiplex communication control circuits are connected to the multiplex communication bus, the multiplex communication control circuit is configured such that the idle detection circuit detects an idle for a certain period of time and the carrier sense. When the detection circuit does not detect the carrier sense, it is possible to start transmission of the communication signal on the multiplex communication bus at any timing at any time, and during the transmission of the communication signal, the collision detection circuit When a collision of communication signals on the multiplex communication bus is detected, a communication signal in a dominant state for a certain period of time is transmitted on the multiplex communication bus,
After making the other multiplex communication control circuit detect the collision, the transmission is stopped, and the multiplex communication control circuit is set to have a length smaller than the idle for a certain period of time and a different length is set for each multiplex communication control circuit. A transmission control circuit capable of retransmitting a communication signal onto the multiplex communication bus when the idle detection circuit detects an idle for a certain period of time, and the transmission control circuit is transmitting or retransmitting a transmission signal. Otherwise, when the communication start signal detection circuit detects the communication start signal, a reception control circuit that starts receiving a communication signal from the multiplex communication bus is provided. Multiplex control device.