JPH0795222A - Communication equipment - Google Patents

Abstract

PURPOSE:To provide a communication equipment in which the abnormality of a transmission line can be recognized by a simple constitution in a data communications system such as a CSMA/CD system. CONSTITUTION:A reception control part 20 of the communication equipment is provided with a CS detecting part 28 which outputs a transmission permitting signal IDLE for permitting the transmission of transmission data to a transmission control part 16, and an SOF error detecting part 30 which compares the transmission data transmitted by the transmission control part 16 and fetched from a transmission line with the prescribed pattern of a transmission control character SOF indicating the start of the transmission data, and outputs a SOF error signal ERR indicating the abnormality of the transmission line when they do not match. Then, the CS detecting part 28 permits the transmission of the transmission data when the transmission line is successively set in an active or in-active level in more than a prescribed time. Thus, the abnormality of the transmission line can be detected by the SOF error detecting part 30 without providing a fail detecting circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to CSM for performing serial communication by pulse-width modulating digital data bit by bit.
The present invention relates to a communication device used in a data communication system such as an A / CD system.

[0002]

2. Description of the Related Art Conventionally, when transmission data from another communication device is not flowing on a transmission line, transmission of the transmission data is started, and during transmission of the transmission data, the transmission data being transmitted and another communication device are being transmitted. CSMA / CD system data communication that monitors the collision of the transmission data with the transmission data from the transmission line on the transmission line, stops the transmission of the transmission data when the transmission data collides, and restarts the transmission of the transmission data after a lapse of a predetermined time. Communication devices used in systems are known.

Further, in such CSMA / CD system, since the communication device which has transmitted the transmission data at the time of the transmission data collision simultaneously stops the transmission, in recent years, when the transmission data collides, the transmission data having a high priority is transmitted. A data communication system is considered in which a transmitting communication device continues to transmit transmission data, and a communication device transmitting low-priority transmission data stops transmitting transmission data. For example, the J1850 standard, which is an international standard, is also known.

This J1850 standard is based on the above CSMA / C.
A non-destructive arbitration function is added to a D-type data communication system, and a communication device satisfying this standard determines whether or not the transmission data output by itself is flowing through a transmission line. Check every bit,
If the same data as the transmission data output by itself is flowing on the transmission line, the transmission of the transmission data is continued, and if the same data as the transmission data output by itself is not flowing on the transmission line, the transmission data is transmitted. To cancel.

That is, as shown in FIG. 7 (a), J185
In the 0 standard, "1" of digital data is "HL".
The pattern of "L" and "0" of digital data is "H".
It is transmitted on the transmission line in the pattern of "HL". Then, when different communication devices simultaneously start transmission and one communication device sends out "1" and the other communication device sends out "0", the active level (here, High level) is inactive on the transmission line. Since it is more dominant than the level (Low level), the transmission data becomes “HHL” and is received by each communication device. Therefore, the former communication device stops transmission because it does not match the transmission data transmitted by itself, and the latter communication device continues transmission of transmission data.

When a plurality of communication devices simultaneously start transmission in this way, the communication device that has transmitted the transmission data with the lower priority sequentially stops the transmission of the transmission data, and finally only one communication device is transmitted. Will continue to transmit the transmission data. Further, in the data communication system of the J1850 standard, as shown in FIG. 7B, after another communication device finishes sending the transmission data, the transmission control character (EOD / EOF / The communication device can send the transmission data to the transmission line when the low level (CS) including 9 consecutive clocks including IFS) can be confirmed.

By the way, in such a communication system, when an abnormality (failure) occurs in which the level is fixed by short-circuiting the transmission line to the power supply or the ground, it becomes impossible to transmit / receive the transmission data. It is necessary to detect and detect the abnormality and perform a process corresponding to the abnormality.

Of these, when the signal has failed to the inactive level, that is, when the signal level on the transmission line is fixed to the low level, it is apparently the same as the state in which the transmission data can be transmitted. Therefore, the transmission of the transmission data is permitted and the transmission data is transmitted. At this time, since the transmission line has failed, the transmitted transmission data and the data on the transmission line do not match. Therefore, conventionally, an abnormality of this transmission line is detected by checking whether or not the transmission data on the transmission line and a predetermined pattern “HHHHLL” of the transmission control character SOF indicating the start of the transmission data match. It was

When the active level has failed, that is, when the signal level of the transmission line is fixed at the high level, the transmission data cannot be transmitted, and the transmission data transmitted as described above is transmitted. It is impossible to judge the abnormality of the transmission line from the error occurrence state. Therefore, conventionally, by providing a dedicated fail detection circuit on the transmission line separately from the communication device, the state of the transmission line is constantly monitored, and when an active level fail is detected, this is transmitted to the communication device. .

[0010]

As described above, in the conventional communication device, the abnormality of the transmission line is the same when the signal level fails to the active level and when the signal level fails to the inactive level. Nevertheless, they are detected by different methods.Moreover, there is a problem that there is a lot of waste in the device and control because a dedicated fail detection circuit is required for detection when failing to the active level. It was

In order to solve the above problems, the present invention provides
An object of the present invention is to provide a communication device capable of recognizing an abnormality when a transmission line fails to an active level in a data communication system such as CSMA / CD system or J1850 standard without providing a dedicated detection circuit.

[0012]

As shown in FIG. 1, a structure of the present invention for achieving the above object is such that, as shown in FIG. Transmission means for sending out transmission data to which a start data of a predetermined pattern having level inversion is added to the transmission line, and that the signal level of the transmission line is continuous for a predetermined time or longer and no communication device is transmitting the transmission data. On the transmission line when the transmission means transmits the transmission data to the transmission line, and the first transmission permission means permits the transmission of the transmission data from the transmission means to the transmission line when the transmission data is transmitted to the transmission line. Of the start data is compared with the predetermined pattern of the start data, and when they do not match, it is determined that the transmission line is abnormal, and a transmission line abnormality determining means for outputting the determination result. A transmission device for transmitting transmission data from the transmission means to the transmission line when the signal level on the transmission line is at an active level that is the inactive level inverted continuously for a predetermined time or longer. A gist of a communication device is characterized in that a second transmission permitting unit for permitting communication is provided.

[0013]

In the communication device of the present invention configured as described above, the signal level of the transmission line is continuously at the inactive level for a predetermined time or longer, and the first transmission permission means transmits to the transmission line. The data transmission is permitted, or the signal level of the transmission line is continuously in the active level for a predetermined time or longer, and the second transmission permission means permits the transmission of the transmission data to the transmission line. In this case, the transmission means sends transmission data to the transmission line in which start data of a predetermined pattern having a level inversion is added to the head portion of transmission data obtained by pulse-width modulating digital data bit by bit. Then, the transmission line abnormality determination means compares the transmission data on the transmission line with the predetermined pattern of the start data that should be set at the beginning of the transmission data, and when they do not match, the transmission line is abnormal. Then, the result of this determination is output.

In other words, when the signal level of the transmission line is fixed at one level, for example, because the transmission line is short-circuited to the power supply, the start data to be compared with the transmission data has a level inversion. Therefore, no matter which level the transmission line is fixed to, it does not match the transmission data on the transmission line.Therefore, when the transmission data is sent to the transmission line, the transmission line abnormality determination means determines that the transmission line is abnormal. It is determined that

[0015]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a block diagram showing the configuration of a vehicle communication system and each part of an embodiment to which the present invention is applied.

As shown in FIG. 2A, the vehicular communication system according to the present embodiment includes a master node, a column node for transmitting information on switches around the column (headlight switch, etc.) to the master node, and a meter panel. A meter node that sends information such as warning lamps to the master node,
Various nodes A, B, C, etc., such as suspension nodes, which transmit the suspension state to the master node and receive suspension control information from the master node,
They are connected via a transmission line L.

On the transmission line L, serial bidirectional communication is performed by the pulse width modulation method (PWM),
The signal level is Low level when no node is transmitting (inactive), and High (active) level appears when any one node is transmitting. Further, the communication between the respective nodes is performed according to a predetermined communication procedure (J1850 standard), and the transmission data used for the communication includes a transmission control character SOF indicating the start of the transmission data, a destination and a source address. Identifier ID, 0 to 9 bytes of user data Dn, error detection code CRC, transmission control character EO indicating the end of user data including error detection code CRC
D, response information RSP indicating the reception state, transmission control character EOF indicating the end of transmission data, transmission control character IFS for synchronizing each node when transmitting transmission data continuously, and the like. It is transmitted in the format shown in FIG.

Next, each node A, B, C ...
As shown in (b), an electronic control unit (hereinafter simply referred to as an ECU) 2 that monitors and controls the states of various parts of the vehicle.
And a communication device 4 for performing data communication with another node via the transmission line L, and a transmission output from the transmission terminal TX of the communication device 4 inserted between the communication device 4 and the transmission line L. It is composed of a D / R (transmission line driver / receiver) 6 which allows data to flow on the transmission line L and inputs the transmission data flowing on the transmission line L to the receiving terminal RX of the communication device 4.

As shown in FIG. 2 (c), the communication device 4 includes an ECU communication receiving section 12 for receiving a transmission request and digital data for transmission from the ECU 2, and a transmission terminal T.
A transmission line transmitter 14 for transmitting transmission data from X,
When the ECU communication reception unit 12 receives a transmission request from the ECU 2, a transmission control unit 16 for transmitting transmission data in which various codes according to the J1850 standard are added to transmission digital data from the transmission line transmission unit 14, A transmission line receiving section 18 for taking in the transmission data on the transmission line L inputted to the receiving terminal RX via the D / R6, and converting the transmission data taken in by the transmission line receiving section 18 into digital data and transmitting the data. Various codes are extracted from the data, and the reception control unit 20 for transmitting the transmission data for reply to the transmission control unit 16 as necessary, and the digital data obtained by the reception control unit 20 are transmitted to the ECU 2. The transmission unit 22 for ECU communication is included.

Here, as shown in FIG. 4, the reception control unit 20 includes a sampling unit 24 for sampling the transmission data received via the transmission line reception unit 18, and a transmission control unit 16 for transmitting data from the transmission line transmission unit 14. When transmitting the transmission data, the transmission data being transmitted and the transmission line receiving unit 1
8 compares the received transmission data bit by bit, and if the transmission data do not match, the transmission data comparison unit 26 that outputs a signal ARB to the transmission control unit 16 to stop the transmission of the transmission data; The transmission control unit 16 and the CS detection unit 28 that checks whether or not the transmission data can be transmitted to the line L (carrier check) and notifies the transmission control signal 16 of the result by the transmission permission signal IDLE. While the transmission data is being transmitted from the transmission line transmission unit 14, the transmission data received by the transmission line reception unit 18 is checked, and if it does not match the predetermined pattern of the transmission control character SOF indicating the start of the transmission data, the SOF error is detected. When the SOF error detection unit 30 that outputs the signal ERR and the transmission data from another node are being received, each transmission control is performed based on the received transmission data. A transmission control character detection unit 32 that detects a character and outputs a timing signal, and each information is extracted from the transmission data received according to the timing signal detected by the transmission control character detection unit 32. The reception message processing unit 36 determines whether there is an error detection code CRC, processing for the response information RSP, demodulation of pulse-width modulated user data, and the like.

Then, the transmission control unit 16 has the CS detection unit 2
In accordance with the transmission permission signal IDLE output from the transmission line L
Is transmitted, the transmission line transmitter 14 transmits the transmission data, and if transmission is impossible, the transmission data transmission is postponed for a predetermined period. Further, during transmission of transmission data, the transmission data comparison unit 26 sends a transmission stop signal ARB.
When is output, the transmission control unit 16 immediately stops the transmission.

Next, the CS detector 2 which is the main part of the present invention
8, SOF error detection unit 30, and sampling unit 2
4 is shown in detail in FIG. As shown in FIG. 5, first, the sampling unit 24 is a 9-bit shift register that samples the serial transmission data received by the transmission line receiving unit 18 by the system clock CLK from a transmission circuit (not shown) and converts it into parallel data. 38, it is reset when the beginning of the transmission data received by the transmission line receiving unit 18 is detected, and thereafter, every time 3 clocks are counted, that is, the 1-bit data pulse-width-modulated in the communication apparatus of this embodiment is 3. Since the sampling is performed by the clock, a bit timing generation circuit 42 that outputs a timing signal that becomes a High level for one clock width is provided at each bit boundary.

Next, the CS detector 28 shifts the NOR circuit 44, which shifts the output to the High level when the outputs of the shift register 38 are all at the Low level, that is, when the transmission line L is at the Low level for 9 consecutive clocks. When the output of the register 38 is all High level, the output becomes High level AN
The OR circuit 48 and the bit timing generation circuit 42, in which any one of the outputs of the D circuit 46, the NOR circuit 44, and the AND circuit 46 is at the High level, the output becomes the High level.
Of the AND circuit and the output of the OR circuit 48 are both at the high level, and the AND circuit 50 outputs the high level. The output of the AND circuit 50 is the transmission permission signal I.
It is input to the transmission control unit 16 as DLE.

Further, the SOF error detecting section 30 outputs when the output of the lower 6 bits of the shift register 38 is "HHHHLL" which is the pattern of the transmission control character SOF.
A signal S indicating the transmission start timing of the transmission data output from the transmission control unit 16 and the logic circuit 52 that becomes Low level.
An SO that outputs a high-level timing signal after being activated by TR and 6 clocks later, that is, when the first 6 bits of the received transmission data are set in the shift register 38
F determination signal generation circuit 54, SOF determination signal generation circuit 54
Of the AND circuit and the output of the logic circuit 52 are both at the high level, and the AND circuit 56 outputs the high level. Then, the output of the AND circuit 56 is input to the transmission control circuit 16 and the reception message processing unit 36 as the SOF error signal ERR.

That is, the communication apparatus of this embodiment can transmit the transmission data only when the transmission is permitted by the transmission permission signal IDLE. However, the transmission permission signal IDLE is transmitted through the transmission line L in a predetermined manner. Continuously for more than an hour
When it is at Low level, that is, when no node is transmitting the transmission data, or when the transmission line L is failing to the inactive level, or when the transmission line L is continuously at High level for a predetermined time or more, that is, , Is output when the transmission line L has failed to the active level.

Then, the transmission control unit 16 causes the transmission permission signal I
When transmission of the transmission data is started according to DLE, the reception control unit 20 takes in the transmission data from the transmission line L, and the SO
The F error detection unit 30 determines whether the received transmission data matches a predetermined pattern of the transmission control character SOF indicating the start of the transmission data.

Here, if the transmission is normally performed, the beginning of the transmission data fetched from the transmission line L coincides with the predetermined pattern of the transmission control character SOF, and thus the SOF.
The error signal ERR is not output and the transmission is continued. However, when the transmission line L has failed to either the active / inactive level, the data to be received is all high level or all low level, so naturally it does not match the predetermined pattern of the transmission control character SOF. The SOF error signal ERR is output as an abnormality of the transmission line L.

The SOF error signal ERR is transmitted to the ECU 2 via the transmission control unit 16 and the reception message processing unit 36, and the transmission control unit 16 immediately stops transmission of transmission data. Further, in the case of the suspension node, for example, in the case of the suspension node, the ECU 2 cannot obtain information for controlling the suspension from the master node, and therefore, the process of setting the suspension strength to a predetermined value is executed.

As described above, in the conventional communication device, as shown in FIG. 6A, the signal level of the transmission line L taken in by the receiving terminal Rx is continuously inactive for a predetermined time or longer. Since the transmission of the transmission data was permitted only in this case, the transmission data could not be transmitted when the signal level of the transmission line L taken in at the receiving terminal Rx was the active level (the dotted line in the figure). However, in the communication device of the present embodiment, transmission of transmission data is permitted even when the signal level of the transmission line L captured at the reception terminal Rx is continuously at the active level for a predetermined time or longer. . Then, in this case, when the transmission data is transmitted, as shown in FIG. 6B, the transmission control character SOF indicating the beginning of the transmission data is transmitted.
When the SOF error is transmitted, the SOF error detection unit 30 of the reception control unit detects the SOF error and immediately stops the transmission of the transmission data. By raising it, it is possible to detect when the transmission line L fails to the active level without providing a special fail detection circuit. Then, this method is the same as the detection method in the case of failing to the inactive level, which is performed in the conventional device.

Therefore, according to the communication apparatus of the present embodiment, even if the transmission line L fails to either the active or inactive level, the abnormality of the transmission line L can be detected and processed by the common method. Therefore, control can be performed without waste. Further, the communication device of the present embodiment transmits the transmission data so that the SOF error, which has conventionally been generated only when the inactive level failure occurs, is also generated when the active level failure occurs. Only the case where the transmission line L is continuously at the active level for a predetermined time or longer is added to the conditions for permitting, and the device can be downsized by the fact that it is not necessary to provide a fail detection circuit that is conventionally provided for exclusive use. It is possible,
For example, it is also advantageous when the device is integrated into an IC.

[0031]

As described above, in the communication device of the present invention, the transmission of the transmission data is performed not only when the signal level of the transmission line is continuously at the inactive level for a predetermined time or longer, but also when the signal level of the transmission line is set to the second level. The transmission permission means makes it possible even when the active level is continuously maintained for a predetermined time or longer.
Further, the transmission line abnormality determination means compares the transmitted transmission data on the transmission line with a predetermined pattern of start data that should be set at the beginning of the transmission data, and when they do not match, the transmission line is abnormal. It has been determined.

Therefore, according to the communication apparatus of the present invention, the transmission data is sent to the transmission line regardless of whether the transmission line fails at the active level or the inactive level. It is possible to determine the abnormality of the transmission line. That is, since the failure of any level is judged by the same transmission line abnormality judging means, control can be performed without waste.

Further, the communication apparatus of the present invention uses the second transmission permitting means in order to make the transmission path abnormality judging means, which conventionally judges only the inactive level fail, also judge the active level fail. However, the device can be downsized by the fact that it is not necessary to provide a fail detection circuit, which has been conventionally provided exclusively, which is also advantageous when the device is integrated into an IC.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a data communication system and each unit of this embodiment.

FIG. 3 is an explanatory diagram showing a configuration of transmission data transmitted and received in the communication device of this embodiment.

FIG. 4 is a block diagram showing a configuration of a transmission control unit in FIG.

5 is a circuit diagram showing details of a CS detection unit, an SOF error detection unit, and a sampling unit in FIG.

FIG. 6 is an operation explanatory diagram illustrating a transmission operation of transmission data in the communication device according to the related art and the present embodiment.

FIG. 7 is an explanatory diagram showing a format of transmission data of J1850 standard on a transmission line.

[Explanation of symbols]

4 ... Communication device 16 ... Transmission control unit 2
0 ... Reception control unit 24 ... Sampling unit 26 ... Transmission data comparison unit
28 ... CS detection unit 30 ... SOF error detection unit 32 ... Transmission control character detection unit 36 ... Received message processing unit 38 ... Shift register 42 ... Bit timing generation circuit 54 ... SOF determination signal generation circuit

Claims (1)

[Claims] 1. Transmission means for transmitting transmission data to a transmission line, in which start data of a predetermined pattern having level inversion is added to the head portion of transmission data obtained by pulse-width-modulating digital data bit by bit. When the signal level of the transmission line is at an inactive level which indicates that no communication device is continuously transmitting the transmission data for a predetermined time or more, the transmission means permits transmission of the transmission data to the transmission line. 1 when the transmission permitting means sends the transmission data to the transmission line,
The transmission data on the transmission line is compared with a predetermined pattern of the start data, and when they do not match, it is determined that the transmission line is abnormal, and a transmission line abnormality determination means for outputting the determination result, A communication device provided, wherein when the signal level on the transmission line is at an active level that is the inactive level inverted for a predetermined time or more continuously, transmission of transmission data from the transmission means to the transmission line is permitted. A communication device comprising: