JP4476411B2 - Data communication method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data communication method and apparatus for transmitting data from a transmission unit to a reception unit via a predetermined signal line, and more particularly to a data communication method and apparatus for transmitting data using a Manchester code.
[0002]
[Prior art]
Various self-synchronous encoding transmission systems are known in which a serial binary signal to be transmitted in a synchronous communication system or the like is transmitted by including a clock for synchronization on the receiving side. Among them, the Manchester encoding method is known as an encoding transmission method used in a CSMA / CD LAN or the like. Manchester code is a system in which 1-bit data is made redundant into 2 bits by using two pairs of different logic elements. Data “0” is “1” for the first half logical element and “0” for the second half logical element. In the data “1”, the first logical element is represented by “0” and the second logical element is represented by “1”. As a result, the high and low levels are always inverted at the center of the bit interval, and the continuation of the logic elements of the same level is within two times. By checking this with the reproduction clock, it is possible to perform an error check in bit units. .
[0003]
[Problems to be solved by the invention]
In the conventional Manchester encoding method, a retransmission request is sent from the reception side to the transmission side as a code error occurs when the first and second logical elements are at the same level due to the influence of external noise, etc. When the transmission side receives a retransmission request, the same data is retransmitted again. For this reason, data transmission is bidirectional, and the communication procedure and the configuration of the transmission / reception apparatus are complicated.
[0004]
In addition, a differential method is generally known as one of techniques for removing external noise (common mode noise) in a communication system. In this communication method, common mode noise is removed by detecting a voltage difference between two communication lines on the receiving side and determining a logic level of the signal. A differential Manchester code system in which this differential system is applied to Manchester codes is also known. However, in the differential communication method, when one of the two signal lines becomes impossible to transmit, it is difficult to detect the differential voltage on the receiving side, and in the worst case, the data cannot be decoded. is there.
[0005]
The present invention has been made to solve such problems, and an object thereof is to provide a data communication method and apparatus having high noise resistance and an excellent fail-safe function against signal line disconnection and the like. To do.
[0006]
[Means for Solving the Problems]
The data communication method according to the present invention includes a first code comprising a Manchester code comprising 1-bit data by a pair of first half elements and second half elements having different logic levels via a first signal line from a transmission section to a reception section. And the second data obtained by inverting the logic of the first data via the second signal line, and the data received via the first signal line on the receiving side and the data Compared with the data received via the second signal line, if either element of both data indicates the same logic level, the first half element and the second half element indicate the same logic level. it is determined that an error has occurred in the received data of the person who is normally treated as a correct received data the other of the received data, received from one of the first and second signal lines Characterized by being adapted to process the received data from the other signal line when the data is interrupted.
[0007]
The data communication apparatus according to the present invention includes a transmission unit, a reception unit, and first and second signal lines that connect the transmission unit, and the transmission unit includes first half elements having different logic levels. The first data consisting of Manchester code that constitutes 1-bit data with a pair of latter elements and the second data obtained by inverting the logic of the first data are applied to the first and second signal lines, respectively. And the receiving unit compares the logical levels of the first data and the second data received via the first and second signal lines, respectively , and correct the other received data to determine that an error has occurred in the received data towards the element first and second halves element indicates the same logic level when the logic level showed the same level Normally processed as reception data, and wherein the when the received data from one of the first and second signal line is interrupted is to process the received data from the other signal line.
[0008]
According to the present invention, since the first data and the second data received through the first and second signal lines are data obtained by inverting the logic levels, external noise (common mode noise) is obtained. ) Inverts the logic level of the data, the influence always appears only in one data, and the logic level of the other data does not change. In the present invention, when the logical levels of the two data are compared and both logical levels indicate the same level, it is determined that an error has occurred in one of the received data from the code state of both data, Since the other received data is normally processed as correct received data, there is no need to request data retransmission. For this reason, data communication can be unidirectional communication, and the transmission side can be a simple hardware configuration dedicated to transmission and the reception side can be dedicated to reception, and the communication procedure can be simplified, so the program storage area Less. Thereby, the cost reduction of the whole communication system can be aimed at.
[0009]
Further, according to the present invention, when the reception data from the first and second signal lines are individually processed and the reception data from either one of these signal lines is interrupted, the data from the other signal line is interrupted. Since the received data is processed, even if one of the signal lines is disconnected, communication is not immediately disabled, and a communication method having an excellent fail-safe function can be realized.
[0010]
In a more specific aspect of the present invention, when the reception data from one of the first signal line and the second signal line is interrupted, the other reception data is used to comply with the rules of Manchester code and are in bit units If there is no bit error after the error check in step 1, the other received data is processed normally. Thereby, even when one signal line is disconnected, data communication can be performed without impairing the reliability of the received data. When an error occurs continuously for a predetermined time in the received data from one of the first and second signal lines, a warning display or a warning sound can be output.
[0011]
In the unidirectional communication, when the first and second data are updated to the latest data at a predetermined cycle and transmitted from the transmission unit to the reception unit, the reception data received on the reception side in normal processing The received data is processed as reception confirmed data only when there is no bit error continuously for the predetermined number of times and the same value continuously for the predetermined number of times. According to such a configuration, even when an error occurs in one received data, the correct received data can be obtained by the other received data, so that there is no bit error continuously for a predetermined number of times, and reception confirmed data is obtained. The time required to complete the process can be shortened and the response performance on the receiving side can be improved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.
FIG. 1 is a diagram showing a schematic configuration of a data communication apparatus according to an embodiment of the present invention. This data communication apparatus includes a transmission unit 1, a reception unit 2, and a pair of signal lines 3a and 3b connecting them. Assuming a LAN system for automobiles, the transmission unit 1 is, for example, an engine control unit, and the reception unit 2 is a combination meter or the like. Communication from the transmission unit 1 to the reception unit 2 via the signal lines 3a and 3b is unidirectional communication. The signal lines 3a and 3b include data A based on non-inverted Manchester code and data B composed of inverted Manchester code, respectively. Are transmitted.
[0013]
For example, as illustrated in FIG. 2, the transmission unit 1 includes an XOR gate 11 that exclusively ORs transmission data including an NRZ (Non-Return to Zero) code and a clock CK1 having the same cycle as the data cycle. The inverter 12 for inverting the output of the XOR gate 11 is provided. As shown in FIG. 3, the XOR gate 11 obtains data A composed of non-inverted Manchester code by taking the exclusive OR of the transmission data and the clock CK1, and by inverting this with the inverter 12, the data B is obtained. The transmission unit 1 transmits the data A and B to the reception unit 2 via the signal lines 3a and 3b.
[0014]
The receiving unit 2 compares the logical levels of the data A and B, and if both logical levels indicate the same level, it determines that an error has occurred in one of the received data from the code state of both data. The other received data is processed as correct received data, and when the received data from one of the signal lines 3a and 3b is interrupted, the received data from the other signal line is processed.
[0015]
The receiving unit 2 is configured as shown in FIG. 4, for example. The data A is binarized at a predetermined threshold level TH1 by the waveform shaping circuit 21, and the waveform of the data B is binarized at a predetermined threshold level TH2 by the waveform shaping circuit 22. Waveform shaping. The outputs A ′ and B ′ of the waveform shaping circuits 21 and 22 are input to the clock recovery circuits 23 and 24, respectively. The clock recovery circuit 23 extracts a clock component included in the data A ′ and multiplies it to regenerate the clock CK2 having a frequency twice that of the clock CK1 described above. Similarly, the clock recovery circuit 24 extracts a clock component included in the data B ′ and multiplies it to reproduce the clock CK3 having a frequency twice that of the clock CK1 described above.
[0016]
Further, the output A ′ of the waveform shaping circuit 21 is sampled at the edge between the edges of the waveform by the regenerated clock CK 2 and is sequentially stored in the two-stage D-type flip-flops 25 and 26. Similarly, the output B ′ of the waveform shaping circuit 22 is sequentially stored in the two-stage D-type flip-flops 27 and 28 in accordance with the recovered clock CK3. The 4-bit data stored in these D-type flip-flops 25 to 28 is supplied to the determination circuit 29. The determination circuit 29 is connected to the D-type flip-flop every time a pair of the first half element and the second half element constituting 1-bit data is set in the D-type flip-flops 25 to 28 every two cycles of the clocks CK2 and CK3. The received data is determined based on the state of the 4-bit data stored in the blocks 25 to 28, and the received data of the NRZ code is output. Further, the determination circuit 29 identifies the disconnection of the signal lines 3a and 3b from the 4-bit data pattern, and when it is determined that the disconnection has occurred, the determination circuit 29 drives the warning notification unit 30 including a display device, a warning sound generator, and the like.
[0017]
Next, the operation of this data communication apparatus will be described.
FIG. 5 shows a timing chart of signals at various parts for explaining the operation of this apparatus. FIG. 6 is a diagram for explaining the relationship between the data values stored in the D-type flip-flops 25, 26, 27, and 28 in FIG. 4 and the determination result in the determination circuit 29. Two bits on the right side of the square indicate the preceding bits (first half element), and two bits on the left side indicate the following bits (second half element). FIGS. 6A and 6F show a state in which there is no bit error, and FIGS. 6B to 6E and FIG. 6G and FIG. The error in the first half of FIG. 5 is an example in which the element in the first half of the data A ′ is erroneously changed from 0 to 1, and corresponds to the pattern in FIG. The error in the latter half of FIG. 5 is an example in which the latter half of the data B ′ is erroneously changed from 1 to 0, and corresponds to the pattern in FIG.
When there is no sign error in the data A and B transmitted through the signal lines 3a and 3b, the data A 'and B' always have different logic levels, so a pair of 1-bit data indicating data When the elements are stored in the D-type flip-flops 25, 26, 27, and 28, these four data have different logic levels in the upper, lower, left, and right directions as shown in (a) or (f) of FIG. Then, when the first half element of the data A ′ is “1” and the second half element is “0” as shown in FIG. 5A, it is determined that the received data is “0”. Thus, when the first half element of data A ′ is “0” and the second half element is “1”, it is determined that the received data is “1”.
[0018]
As shown in FIG. 5, when in-phase noise is superimposed on the signal lines 3a and 3b, a bit error occurs in one of the data A 'or B', and FIGS. 6 (b) to 6 (e) and 6 (g). As indicated by hatching in (j), the logical levels of the data A ′ and B ′ are equal. In this case, since the other data A ′ or B ′ is correct data in which the logic levels of the first and second elements are different, the received data is based on this correct data. ) Can be determined as “0”, and in the cases (g) to (j) in FIG.
[0019]
If the error continues for a predetermined time, the signal line 3a or 3b for transmitting the data in which the error has occurred is disconnected, or noise generated at a certain period is always on the same position in the communication data. For example, when errors of the same level or the same pattern (keep level 0, etc.) continue for a predetermined time, it is determined that there is a possibility of disconnection, and the warning notification unit 30 A warning is displayed or a warning sound is output. In this case, when there is a bit error, the time required to confirm the reception of the latest data is longer than when using the two signal lines 3a and 3b, but data transmission is performed using the normal signal line. Can be continued as is.
[0020]
In the above embodiment, the transmission unit 1 and the reception unit 2 are both configured by hardware. For example, as illustrated in FIG. 7, the transmission unit 1 is configured by a transmission driver 41 and a one-chip microcomputer 42. At the same time, the receiving unit 2 can be constituted by the receiving driver 51, the one-chip microcomputer 52, and the alarm notification unit 30. In this case, the transmission unit 1 realizes the coding from the NRZ code to the Manchester code and the generation of the inverted Manchester code by software by the one-chip microcomputer 41, and the reception unit 2 converts the inverted and non-inverted Manchester code to the NRZ code. Decoding and error checking can be realized by software using the one-chip microcomputer 52, and the hardware configuration is simplified.
[0021]
【The invention's effect】
As described above, according to the present invention, when the logical levels of two data are compared and both logical levels indicate the same level, an error is detected in one of the received data from the code state of both data. Since it is determined that it has occurred and the other received data is processed as correct received data, there is no need to request retransmission of data. For this reason, unidirectional communication is sufficient for data communication, and the system configuration can be simplified.
[Brief description of the drawings]
FIG. 1 is a block diagram of a data communication apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a transmission unit in the apparatus.
FIG. 3 is a data waveform diagram for explaining the operation of the transmission unit;
FIG. 4 is a block diagram showing a configuration of a receiving unit in the apparatus.
FIG. 5 is a data waveform diagram for explaining the operation of the receiving unit;
FIG. 6 is a diagram for explaining an operation of the receiving unit.
FIG. 7 is a block diagram of a data communication apparatus according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transmission part, 2 ... Reception part, 3a, 3b ... Signal line.

Claims (6)

The first data consisting of the Manchester code that constitutes 1-bit data with a pair of the first half element and the second half element having different logic levels is transmitted via the first signal line from the transmission section to the reception section, and the second data Transmitting second data obtained by inverting the logic of the first data via a signal line;
The data received via the first signal line on the receiving side is compared with the data received via the second signal line, and either element of both data indicates the same logic level. If the first half element and the latter half element indicate the same logic level, it is determined that an error has occurred in the received data, and the other received data is processed normally as the correct received data. A data communication method characterized in that when the reception data from one of the two signal lines is interrupted, the reception data from the other signal line is processed.   When the received data from either the first signal line or the second signal line is interrupted, the other received data is used to check the error in bit units according to the rules of Manchester code. 2. The data communication method according to claim 1, wherein if there is no error, the other received data is normally processed.   The warning notification process is executed while processing the other received data when an error occurs continuously for a predetermined time in the received data from one of the first signal line and the second signal line. 3. The data communication method according to claim 1, wherein the data communication method is a data communication method. A transmission unit, a reception unit, and first and second signal lines connecting them;
The transmission unit includes first data composed of a Manchester code that forms 1-bit data with a pair of first and second half elements having different logic levels, and second data obtained by inverting the logic of the first data. Are respectively output to the first and second signal lines,
The receiving unit compares the logic levels of the first data and the second data received via the first and second signal lines, respectively, and the logic level of one element of both data is When the same level is indicated, it is determined that an error has occurred in the received data in which the first half element and the second half element indicate the same logical level, and the other received data is normally processed as correct received data. A data communication apparatus characterized by processing reception data from the other signal line when reception data from either one of the first and second signal lines is interrupted. When the reception data from one of the first signal line and the second signal line is interrupted, the reception unit uses the other reception data to check an error in bit units according to the rules of Manchester code. 5. The data communication apparatus according to claim 4, wherein the other received data is normally processed if there is no bit error after performing. The receiving unit executes a warning notification process while processing the other received data when an error occurs in the received data from either the first signal line or the second signal line for a predetermined time continuously. The data communication device according to claim 4 or 5, wherein

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