JPH0851413A - Data communication equipment - Google Patents

Abstract

PURPOSE:To provide a data communication equipment having masterslave constitution capable of preventing the other transmission from being interrupted when a noise is generated especially in a non-signal section. CONSTITUTION:Plural slave stations 12 is connected to one master station through transmission lines 13 and a signal of a prescribed format consisting of SOF, plural basic data blocks, ED, ACK, NCK, and EOF areas is transmitted from the master station. Each slave station 12 is provided with a format checking circuit 22 and error checking circuits 23, 24 and the gates of respective AND circuits 26, 27 are opened by 'H' signals outputted from these checking circuits 22 to 24 to transmit AKC from a timing signal generating circuit 25. When an output from the circuit 22 is 'H' and an 'L' output is obtained from the circuit 26, NCK is transmitted from an AND circuit 28, and when the abnormality of the format is confirmed, both ACK and NCK are not transmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master station consisting of a central control unit and driving devices for driving commands of various actuators installed in vehicles such as automobiles, information such as sensor signals and switch information. The present invention relates to a master-slave configuration multiplex communication device that transmits / receives data to / from a plurality of slave stations that are set correspondingly to a sensor, a switch, and the like. In particular, transmission / reception of a transmission signal between a transmitter and a receiver is performed. The present invention relates to a data communication device that enables efficient operation.

[0002]

2. Description of the Related Art In a data transmission / reception system, when transmitting data from a transmitter to a receiver, the transmitter receives a response from the receiver for each transmission data transmitted from the transmitter, Communication means for transmitting and receiving data are known. in this case,
The receiver side confirms the reception of the data signal from the transmitter and transmits a predetermined response to the transmitter. As means for such a response, for example, Japanese Patent Laid-Open No. 60-
The data communication method disclosed in No. 236337 is known. That is, in this data communication method, a response area is set in the last part of the transmission data, and an acknowledgment (ACK) or a negative acknowledgment (N
CK) is returned from the receiver side to the transmitter side.

In addition, the German company Bosch proposed C
In AN (Controller Area Network), when an error occurs in the data signal transmitted from the transmitter side to the receiver side, the receiver side transmits a dedicated frame at the time of error to the transmitter side. ing.

Then, in the data communication method of the above-mentioned Japanese Patent Laid-Open No. 60-236337, a negative response is generated, and CA
The condition that an error frame occurs in N is that an error is detected in the data signal received on the receiving side. For example, in CAN, an error frame is transmitted when one or more of bit error, stuff error, CRC error, form error, ACK error, etc. occur.

However, such an error detected on the receiver side is easily generated by noise,
For example, when noise is generated during the transmission of data and a negative response or an error frame is transmitted, the data frame is only destroyed and other communication is less affected. However, noise is generated during a no-signal period generally called idle, and when this noise is received by a receiver, this noise may be erroneously recognized as the beginning of a frame. When noise is erroneously recognized as the beginning of a frame, a negative response or error frame is always returned, and data from other transmitters will be sent for a period of one frame length or longer after the noise is generated. Transmission is prohibited. Even if the signal is transmitted to the transmission line by another transmitter, the transmission data is destroyed due to the presence of the negative response or the error frame, and the transmission efficiency is significantly deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is particularly desirable to prevent transmission from other transmitters when noise is generated during a no-signal period. A data communication device that enables efficient use of a transmission line and effectively configures a master-slave multiplex communication network, for example, in a vehicle with a high noise generation rate. It is the one we are trying to provide.

[0007]

In the data communication apparatus according to the present invention, the transmission means sends out the transmission signal of the predetermined format to the transmission line, and the reception means receives the transmission signal from the transmission means. In the communication network, the format confirmation means for confirming the format of the transmission signal transmitted through the transmission path, the error confirmation means for detecting a signal error from the transmission signal transmitted through the transmission path, and the format confirmation means for normal format And a positive response sending means for sending a positive response to the transmission line in a state where the error confirmation means does not confirm the occurrence of an error, and the format confirmation means confirms that the format is normal, and the error confirmation means Negative response sending that sends negative response to the transmission line when error occurrence is confirmed Configured and means, when an abnormality of the format is identified in the format check means, any of the positive and negative responses are prevented from being delivered.

[0008]

For example, most of the noise generated in the vehicle is of a pulse type such as surge, and therefore it is unlikely to continue to be generated during the transmission period of the data frame to be transmitted. Focusing on this point, when an error is detected on the receiving means side, it is determined whether the received message is transmitted from the transmitting means or is erroneously recognized due to noise. Then, when an error is detected in a state where it is determined that there is no abnormality in the reception format, a negative response is generated, and when it is determined that the reception format is normal and false recognition due to noise, an affirmative response is also issued. Negative response is not performed, and other messages are not destroyed so that transmission efficiency is ensured.

Noise that frequently occurs in a vehicle is
It is often caused sporadically due to ignition noise, flyback pulses generated by motors, solenoids, and the like. Therefore, a major difference on the transmission path between the case where noise is generated during message transmission and the case where noise is generated during transmission is whether or not the one close to the predetermined frame format is transmitted. Therefore, in the signal received by the receiving means, a characteristic part of the format, for example, SOF (Start Of Frame), EOD (End O)
f Data), message length (length from SOF to EOD), and whether the transmitted format is normal by judging whether or not the code for bit synchronization has a predetermined waveform shape. It can be identified by the format confirmation means.

The negative response from the receiving means destroys other messages mainly when erroneously recognizing the start of transmission due to noise generated during non-transmission, and therefore the format confirming means does not transmit in the receiving means. Negative response is not sent when it is recognized that noise is generated. Even if an error occurs in this way, a negative response is not always returned, but a negative response is returned only when at least the main shape of the format is recognized to be normal, so even in a noisy environment. The deterioration of transmission efficiency can be effectively suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a communication network installed in a vehicle, for example, one master station 11 set corresponding to a central electronic control unit and the like, motors and solenoids, and loads such as sensors and switches. A plurality of slave stations 121, 122, ... Set corresponding to the respective elements are provided, and the master station 11 and each slave station 121, 122 ,. A master station slave (slave station) network is configured.

The master station 11 includes a protocol control unit 111 and a receiving unit.
The protocol control unit 111 includes a 112 and a transmission unit 113, and is constituted by, for example, a microprocessor that uses a crystal oscillation clock source. The receiving unit 112 is composed of a comparator Co1 which compares the potential of the transmission line 13 with a reference voltage divided by the resistors R1 and R2, and the transmitting unit 113 is composed of a driver capable of three-state output using a transistor. .

The slave stations 121, 122, ... Are divided into a protocol control section 1211 having an input / output port for communication data, a potential of the transmission line 13 and resistors R2 and R4, as represented by the slave station 121. Comparator C for comparing with the applied reference potential
A load element, which is an external actuator 141, is driven by a transistor 1214 that is configured to include a reception unit 1212 configured by o2 and a communication output transistor 1213, and is controlled by the output from the protocol control unit 1211. Further, the detection information from the load element such as the sensor or the switch 142 is input to the protocol control unit 1211, transmission data is created, and the communication transistor 1213 is controlled.

The other slave stations 122, ... Have the same construction as the slave station 121, but are connected with specific load elements such as actuators, sensors, switches, etc., respectively.
These load elements are driven by a command from each slave station, and information from sensors, switches, etc. is input to the corresponding slave stations.

FIG. 2 shows the construction of the slave stations 12 (121, 122, ...) In more detail. The receiving circuit 21 to which the output from the comparator Co1 is supplied is mainly composed of a shift register. Only when there is no error, the received data is fetched in the buffer and a signal is output to the transistor 1214 or the like that drives the external actuator 141 or the like. The output signal from the comparator Co1 further includes a format check circuit 22 for detecting a format error, an error check code check circuit 23, and a bit error check circuit 2.
4, further supplied to the timing signal generation circuit 25.

Here, the error check code confirmation circuit 23
Confirms that the received data is garbled. Further, the bit error confirmation circuit 24 confirms, for each bit, whether the received data is confirming the determined code shape or whether each bit length is the determined length.
The timing signal generation circuit 25 manages the operation timings of various internal circuits. However, in this figure, for convenience of explanation, only the output of ACK for positive response and NCK for negative response is output. Shows.

The confirmation signals from the format confirmation circuit 22, the error check code confirmation circuit 23, and the bit error confirmation circuit 24 are supplied to the 3-input AND circuit 26, and the output signal from the AND circuit 26 is supplied. Is supplied to the reception circuit 21 as a reception command signal. The code ACK output from the timing signal generation circuit 25 is input to the AND circuit 27 together with the output from the AND circuit 26, and the code NCK from the timing generation circuit 25 is the format confirmation circuit.
It is input to the AND circuit 28 together with the output from 22, and the output from the AND circuit 26 is also input to the AND circuit 28 in negative logic.

A switch 14 set outside the slave station 12.
Information from load elements such as 2 is input to the transmitting circuit 29, which is driven by the timing signal from the timing signal generating circuit 25 to input from external load elements such as the switch 142 to a predetermined format. To output. The output signal from the transmission unit 113 controls the transistor forming the transmission unit 113 via the OR circuit 30, and the OR circuit 30 is further supplied with the output signals from the AND circuits 27 and 28.

FIG. 3 shows an example of a frame format for explaining the format confirmation circuit 22. This frame first starts with SOF. Then, following this SOF, a lower 4 bits D0 to D3 of the data and a basic block 1 consisting of a 1-bit inversion code obtained by inverting the bit D3 for bit synchronization are set, and further upper 4 bits D4 to D7. , A basic block 2 consisting of a 1-bit inversion code obtained by inverting the bit D7 for bit synchronization follows. And the error check code 4 in the data section
Bits Po to P3 and bit P for bit synchronization
A basic block 3 consisting of a 1-bit inversion code obtained by inverting 3 is followed, and this inversion code also serves as a code EOD indicating the end of data. After that, ACK and NCK
Area is set, and EOF indicating the end of the frame is set last.

FIG. 4 shows a specific example of the structure of the format confirmation circuit 22 when the frame format is used in this way. SOF is stored together with each bit of the basic blocks 1 to 3 of the frame format shown in FIG. And a shift register 40 having a storage stage.

Each stage of the shift register 40 stores the bits held in each stage at the time of error confirmation as shown in the figure. The output from the stage storing the bit D3 of the shift register 40 and its inverted sign is input to the exclusive OR circuit 41. Also, bit D7
And the output from the stage storing the inverted code thereof is inputted to the exclusive OR circuit 42, and further, the bit P3 and the input data subsequent thereto are inputted to the exclusive OR circuit 43. These exclusive OR circuits 41 to 43
The output from each is input to the AND circuit 44.

A format confirmation signal is output from the AND circuit 44. A high level (H) output is obtained when the frame format is normal, and a low level (L) when the format is abnormal. Output is obtained.

The operation of the multiplex communication apparatus adopting the master-slave system configured as above will be described with reference to FIG. First, the master station 11 sends a data signal to the transmission line 13 according to the format shown in FIG.
At the time of outputting up to OD, the data is stored in the shift register in the reception circuit 21 of each slave station 12 in the situation as shown in FIG. Here, the characteristic of the format shown in FIG. 3 is that the last bit of the code SOF indicating the frame start is at the H level, and an inversion signal for bit synchronization adjustment is included in every 5 bits of the data area. .

In such a master-slave multiplex communication device, when communication is normally performed, the signal waveform sent to the transmission line 13 is set as shown in FIG. That is, in the format confirmation circuit 22 as shown in FIG. 4, the inverted signals of the basic blocks 1 to 3 are confirmed by the exclusive OR circuits 41 to 43, and if they are normal, these exclusive OR circuits 41 to 43. Goes to H level, the output to the AND circuit 44 goes to H level, and the format confirmation signal goes to H level indicating normal.
In this state, the other confirmation circuits 23 and 24 are also set to H level indicating that they are normal, and the output of the AND circuit 26 becomes H level.
The level is set, and the acknowledge ACK is transmitted via the AND circuit 27 and the OR circuit 30.

Next, as shown in FIG. 5B, when noise occurs during the format of the transmission waveform and the transmission data is garbled, the format confirmation circuit 22
Although the output signal from the H.V. indicates the H level, the output of the error check code confirmation circuit 23 or the bit error confirmation circuit 23 indicates the L level, and an abnormal determination output is output. Therefore, the output of the AND circuit 26 is set to the L level,
The ACK signal is never output from the AND circuit 27.
However, since the output of the AND circuit 26 is at the L level and the output of the format confirmation circuit 22 is at the H level, the negative response NCK is sent via the AND circuit 28.

Then, as shown in FIG. 5C, when noise occurs during the idle period (when there is no signal) before the frame format, the format confirmation circuit 22 detects an abnormality, and the output from this circuit 22 is detected. It is set to L level. Therefore, since the output of the AND circuit 26 is set to the L level, the output of the AND circuit 27 is set to the L level, and the output of the format confirmation circuit 22 is set to the L level, the output of the AND circuit 28 is set to the L level. Therefore, the negative response (NCK) is not transmitted together with the normal response (ACK).

[0027]

As described above, according to the data communication apparatus of the present invention, a negative response (NC) is generated even when noise may occur except when the transmitting side transmits a message.
K) is not sent to the transmission line. Even if a normal message is sent immediately after the noise is generated, the message is not destroyed, and the transmission efficiency does not deteriorate due to the message destruction. Is minimized.

However, when noise is generated in the characteristic portion of the format or the like, the negative response may not be transmitted even if the noise is during data transmission. However, in such a case, a positive response is not always sent, and therefore it is not possible to judge whether the abnormality is in the slave station or due to noise, but the data from the transmitting side is normal. You can confirm that it was not sent to. The failure of the slave station does not necessarily need to be confirmed for each transmission, and is often judged after several confirmations.
As long as the noise generation period and the transmission period do not completely match,
It is possible to judge the failure of the slave station.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a master-slave network for explaining a data communication device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a slave station in the above network configuration.

FIG. 3 is a diagram illustrating a configuration of a frame format sent to a transmission path.

FIG. 4 is a diagram showing a configuration example of a format confirmation circuit configured in correspondence with the frame format.

FIG. 5 is a signal waveform diagram for explaining the operation of the data communication apparatus according to the above embodiment, where (A) shows a normal state,
(B) is when noise occurs during data transmission, and (C)
Indicates the occurrence of noise during no transmission.

[Explanation of symbols]

11 ... Master station, 111 ... Protocol control section, 112 ... Reception circuit,
113 ... Transmitter, 12, 121, 122, ... Slave station, 21 ... Receive circuit, 22 ... Format check circuit, 23 ... Error check code check circuit, 24 ... Bit error check circuit, 25 ... Timing signal generation circuit, 26- 28 ... AND circuit, 29 ... Transmission circuit, 30 ... OR circuit.

Claims (3)

[Claims] 1. A receiving means for transmitting a transmission signal of a predetermined format to a transmission line, and a receiving means connected to the transmission line for receiving the transmission signal from the transmitting means. The format confirmation unit for confirming the format of the transmission signal transmitted through the transmission line, the error confirmation unit for detecting a signal error from the transmission signal transmitted through the transmission line, and the format confirmation unit confirms that the format is normal. A positive response sending means for sending an affirmative response to the transmission line in a state where the error is confirmed by the error confirmation means, and the format confirmation means confirms that the format is normal, and the error confirmation means generates an error A negative response sending means for sending a negative response to the transmission path in a state where the occurrence is confirmed, When the abnormality of the format is identified in preparative confirmation means, the data communication is characterized in that none of the positive and negative responses was being dispatched device. 2. The transmitting means is composed of one master station, and the receiving means is composed of each of a plurality of slave stations connected to the master station via a transmission line.
The data communication apparatus according to claim 1, wherein multiple communication is performed between the master station and each of the plurality of slave stations. 3. A frame format forming the transmission signal has a plurality of data blocks, each of which is formed by a plurality of bits including a frame start code and a 1-bit inversion bit for synchronizing, arranged in series. The frame end code is set by sequentially setting a positive response area and a negative response area following the data end code. The format confirmation means sequentially stores bit data forming the frame format. 2. The normality or abnormality of the format is determined by a logic circuit which is composed of a shift register which is combined with the inversion bit of each of the plurality of data blocks and the detection signal of the frame start code. Data communication device.