JP2001223677A - Data communication method and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data communication method that has superior fail/safe function with respect to broken signal wire and high noise immunity. SOLUTION: The data communication system consists of a transmission section 1, a reception section 2 and a couple of signal wires 3a, 3b that interconnect them. Data A, consisting of a non-inverted Manchester code and data B consisting of an inverted Manchester code are transmitted from the transmission section 1 to the reception section 2 via the signal wires 3a, 3b respectively. The reception section 2 compares logic levels of the data A, B. When both the logic levels indicate the identical level, the reception section 2 discriminates the occurrence of an error in the received data, depending on the code state of both the data and processes the other received data as correct received data and processes the received data from the other signal line, when the received data from either of the signal wires 3a, 3b are intermitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication method and apparatus for transmitting data from a transmission section to a reception section via a predetermined signal line, and more particularly to a data communication method and apparatus for transmitting data using Manchester codes. About.

[0002]

2. Description of the Related Art Various self-synchronous coded 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 synchronizing on the receiving side. Among them, the Manchester encoding system is known as an encoding transmission system used in a CSMA / CD LAN or the like. The Manchester code is a system in which one-bit data is made redundant by using two different pairs of logical elements into two bits. For data “0”, the former logical element is “1” and the latter logical element is “0”.
In the data "1", the first half logical element is expressed by "0" and the second half logical element is expressed by "1". As a result, the high and low levels are always inverted at the center of the bit section, and the continuation of the logic element of the same level is limited to twice or less. By verifying this with the reproduction clock, it is possible to perform error checking in bit units. .

[0003]

In the conventional Manchester encoding method, when the first logical element and the second logical element are at the same level due to the influence of external noise or the like, a code error occurs on the receiving side. A retransmission request is transmitted to the transmission side, and when the transmission side receives the retransmission request, the same data is retransmitted again. For this reason, data transmission becomes bidirectional, and the communication procedure and the configuration of the transmission / reception device become complicated.

[0004] Further, in a communication system, generally, one of techniques for removing external noise (common mode noise) is disclosed.
One known method is a differential method. In this communication system, common mode noise is removed by detecting a difference voltage between two communication lines on a receiving side and determining a logical level of a signal. A differential Manchester code system in which this differential system is applied to a Manchester code is also known. However, in the differential communication method, if one of the two signal lines becomes unable to transmit, it becomes difficult to detect the differential voltage on the receiving side, and in the worst case, the data cannot be decoded. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to provide a data communication method and apparatus which have a high noise resistance and an excellent fail-safe function against disconnection of a signal line. With the goal.

[0006]

A data communication method according to the present invention transmits a first data consisting of a Manchester code from a transmitting unit to a receiving unit via a first signal line, and transmits a second signal line. Transmitting the second data obtained by inverting the logic of the first data via the first signal line and the data received via the first signal line and the data received via the second signal line on the receiving side. And if both data indicate the same logical level, it is determined from the code state of both data that an error has occurred in one of the received data, and the other received data is regarded as correct received data. Normal processing is performed, and when data received from one of the first signal line and the second signal line is interrupted, data received from the other signal line is processed.

Further, a data communication apparatus according to the present invention comprises a transmitting section, a receiving section, and first and second signal lines connecting the transmitting section and the receiving section, and the transmitting section is made of a Manchester code. First data and second data obtained by inverting the logic of the first data are output to the first and second signal lines, respectively, and the receiving unit outputs the first and second signals.
And comparing the logical levels of the first data and the second data received via the respective signal lines, and when both logical levels indicate the same level, one of the code states of both data is determined. It is determined that an error has occurred in the received data, and the other received data is processed normally as correct received data. When the received data from one of the first and second signal lines is interrupted, the other signal is output. It is characterized by processing received data from a line.

According to the present invention, since the first data and the second data received via the first and second signal lines are data whose logical levels are inverted from each other, external noise ( Even when the common mode noise) inverts the logical level of the data, the effect always appears on only one data, and the logical level of the other data does not change. In the present invention, the logical levels of the two data are compared, and if both logical levels indicate the same level, it is determined from the code state of both data that an error has occurred in one of the received data, Since the other received data is normally processed as correct received data, there is no need to request data retransmission. For this reason, the data communication can be a one-way communication, and the transmission side can have a simple hardware configuration for transmission only, and the reception side can have a simple hardware configuration for reception only. Less. As a result, the cost of the entire communication system can be reduced.

According to the present invention, data received from the first and second signal lines are individually processed, and when data received from one of these signal lines is interrupted, the other signal is processed. Since data received from the line is processed, even if one of the signal lines is disconnected, communication is not immediately disabled, and a communication method excellent in the fail-safe function can be realized.

In a more specific aspect of the present invention, when data received from one of the first signal line and the second signal line is interrupted, the other received data is used to comply with the Manchester code rule. If there is no bit error after performing an error check in bit units, the other received data is processed normally. Thus, even if one of the signal lines 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 data received from either one of the first and second signal lines, a warning display or a warning sound can be output.

In one-way communication, first and second
When the data is updated to the latest data at a predetermined cycle and transmitted from the transmitting unit to the receiving unit, in the normal processing,
Only when the received data received on the receiving side has no bit error for a predetermined number of consecutive times and has the same value for a predetermined number of consecutive times, the received data is processed as reception confirmed data. According to such a configuration, even when an error occurs in one of the received data, correct received data can be obtained by the other received data. Therefore, a state in which there is no bit error continuously for a predetermined number of times continues, and reception confirmed data is obtained. The time required for this can be shortened, and the response performance of the receiving side can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. FIG. 1 is a diagram showing a schematic configuration of a data communication device according to one embodiment of the present invention.
This data communication device includes a transmission unit 1, a reception unit 2, and a pair of signal lines 3a and 3b connecting these. Assuming a LAN system for a vehicle, the transmission unit 1 is, for example, an engine control unit or the like, and the reception unit 2 is a combination meter or the like. The communication from the transmitting unit 1 to the receiving unit 2 via the signal lines 3a and 3b is one-way communication, and the signal lines 3a and 3b respectively include data A using a non-inverted Manchester code and data B including an inverted Manchester code. Is transmitted.

[0013] The transmitting unit 1 includes, for example, as shown in FIG.
An XOR gate 11 that performs an exclusive OR operation on transmission data composed of an RZ (Non-Return to Zero) code and a clock CK1 having the same period as the data period, and an inverter 12 that inverts the output of the XOR gate 11 It is provided with. As shown in FIG. 3, XOR gate 11 obtains data A composed of a non-inverted Manchester code by taking an exclusive OR of transmission data and clock CK1.
Data B is obtained. The transmission unit 1 transmits these data A and B
Is transmitted to the receiving unit 2 via the signal lines 3a and 3b.

The receiving unit 2 compares the logical levels of the data A and B, and if both logical levels indicate the same level, an error has occurred in one of the received data from the code state of both data. And 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.

The receiving section 2 is configured, for example, as shown in FIG. The data A is binarized by the waveform shaping circuit 21 at a predetermined threshold level TH1, whereby
The waveform is shaped, and the data B is shaped into a waveform by being binarized by the waveform shaping circuit 22 at a predetermined threshold level TH2. Outputs A 'and B' of the waveform shaping circuits 21 and 22 are input to clock recovery circuits 23 and 24, respectively. The clock recovery circuit 23 extracts a clock component included in the data A ', multiplies the clock component, and reproduces a clock CK2 having a frequency twice as high as that of the clock CK1. Similarly, the clock recovery circuit 24 also extracts a clock component included in the data B ', multiplies it, and generates a clock CK having a frequency twice as high as that of the clock CK1.
Play 3

The output A 'of the waveform shaping circuit 21 is sampled by the reproduced clock CK2 at the middle of the edge of the waveform and stored in the two-stage D-type flip-flops 25 and 26 in sequence. Similarly, the output B 'of the waveform shaping circuit 22 is the reproduced clock C
According to K3, two-stage D-type flip-flops 27 and 28
Are sequentially stored. These D-type flip-flops 25 to
The 4-bit data stored in 28 is supplied to a determination circuit 29. The determination circuit 29 determines the clock CK2, 3
For each cycle, that is, every time a pair of the first half element and the second half element forming one-bit data is set in the D-type flip-flops 25 to 28, the 4-bit data stored in the D-type flip-flops 25 to 28 The received data is determined based on the data state, and the received data of the NRZ code is output. In addition, the determination circuit 29 identifies a disconnection of the signal lines 3a and 3b from the 4-bit data pattern, and when it is determined that the signal line 3a or 3b is disconnected, drives a warning notification unit 30 including a display device, a warning sound generation device, and the like.

Next, the operation of the data communication device will be described. FIG. 5 is a timing chart of signals of respective units for explaining the operation of this device. FIG. 6 shows the D-type flip-flops 25, 26, 27,
28 is a diagram for explaining the relationship between the value of the data stored in No. 28 and the result of the judgment by the judgment circuit 29. In the figure, the right two bits of the four squares precede the preceding bit (first half element), and the two left ones indicate the two bits. The following bit (the latter half element) is shown. 6 (a) and 6 (f) show a state where there is no bit error, and FIGS. 6 (b) to (e) and (g) to (j) show examples where a bit error has occurred in a hatched portion. The error in the first half of FIG. 5 is an example in which the element of the first half of the data A 'is incorrect 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 element of the data B 'is incorrectly changed from 1 to 0, and corresponds to the pattern of FIG. When there is no code 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. Elements are D-type flip-flops 25 and 2
At the time when the data is stored in 6, 27, and 28, these four data have different logical levels in upper, lower, left, and right as shown in FIG. 6 (a) or (f). When the first half element of the data A 'is "1" and the second half element is "0" as shown in FIG. 11A, it is determined that the received data is "0". As described above, when the first half element of the data A 'is "0" and the second half element is "1", it is determined that the received data is "1".

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. g) to (j), the data A ', B'
Are equal in logic level. In this case, the other data A 'or B' is correct data in which the logic levels of the first half and the second half are different from each other, and the received data is based on this correct data as shown in FIG.
In the case of (e), it can be determined as “0”, and in the cases of FIGS.

If the error continues for a predetermined time,
It is conceivable that 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 at the same position in the communication data. If an error of the same level or the same pattern (keep the 0 level, etc.) continues for a predetermined time, it is determined that there is a possibility of disconnection, and the warning notification unit 3
0 to display a warning or output a warning sound. In this case, if there is a bit error, the time required to determine 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 it is.

In the above embodiment, both the transmitting unit 1 and the receiving unit 2 are configured by hardware.
For example, as shown in FIG.
And the one-chip microcomputer 42, and the receiving unit 2
May be configured by the reception driver 51, the one-chip microcomputer 52, and the alarm notification unit 30. In this case, the transmission unit 1
Then, the coding from the NRZ code to the Manchester code and the generation of the inverted Manchester code are realized by software using the one-chip microcomputer 41, and the receiving unit 2 performs decoding from the inverted and non-inverted Manchester code to the NRZ code and error checking. This can be realized by software using the one-chip microcomputer 52, and the hardware configuration is simplified.

[0021]

As described above, according to the present invention, the logical levels of two data are compared, and if both logical levels indicate the same level, one of the code states of both data is determined. Since it is determined that an error has occurred in the received data and the other received data is processed as correct received data, there is no need to request data retransmission. For this reason,
Data communication is improved by one-way communication, and the system configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of a data communication device according to one embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a transmission unit in the same device.

FIG. 3 is a waveform diagram of data for explaining the operation of the transmission unit.

FIG. 4 is a block diagram illustrating a configuration of a receiving unit in the device.

FIG. 5 is a waveform chart of data for explaining the operation of the receiving unit.

FIG. 6 is a diagram for explaining the operation of the receiving unit.

FIG. 7 is a block diagram of a data communication device according to another embodiment of the present invention.

[Explanation of symbols]

 Reference numeral 1 denotes a transmitting unit, 2 denotes a receiving unit, 3a and 3b: signal lines.

Claims (8)

[Claims] 1. A first data comprising a Manchester code is transmitted from a transmission unit to a reception unit via a first signal line, and the logic of the first data is inverted via a second signal line. Transmitting the second data, comparing the data received via the first signal line with the data received via the second signal line on the receiving side,
When both data indicate the same logical level, it is determined from the code state of both data that an error has occurred in one of the received data, the other received data is processed normally as correct received data, A data communication method, wherein when data received from one of the first and second signal lines is interrupted, data received from the other signal line is processed. 2. When received data from one of the first signal line and the second signal line is interrupted, an error check is performed on a bit-by-bit basis using the other received data in accordance with the Manchester code rule. 2. The data communication method according to claim 1, wherein the other received data is processed normally if there is no bit error. 3. The first and second data are updated to the latest data at a predetermined cycle and transmitted from the transmitting unit to the receiving unit. In the normal processing, received data received on a receiving side is 3. The data communication method according to claim 1, wherein the reception data is processed as reception confirmation data only when there is no bit error for a predetermined number of consecutive times and when the value is the same for a predetermined number of consecutive times. 4. When an error occurs continuously for a predetermined time in data received from one of the first signal line and the second signal line, a warning notification process is executed while processing the other received data. The data communication method according to any one of claims 1 to 3, wherein: 5. A transmitting unit, a receiving unit, and first and second signal lines connecting the transmitting unit and the receiving unit, the transmitting unit comprising: a first data comprising a Manchester code; Outputting the second data obtained by inverting the logic of the data to the first and second signal lines, respectively, wherein the receiving unit receives the second data through the first and second signal lines, respectively. The logical levels of the first data and the second data are compared, and if 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. Normal processing of the other reception data as correct reception data, and processing of reception data from the other signal line when reception data from one of the first and second signal lines is interrupted. Day characterized by Communication device. 6. The reception unit, when reception data from one of the first signal line and the second signal line is interrupted, using the other reception data and following a Manchester code rule. 6. The method according to claim 5, wherein, after performing an error check in units, if there is no bit error, the other received data is processed normally.
A data communication device as described. 7. The transmission unit updates the first and second data to the latest data at a predetermined cycle and transmits the updated data to the reception unit. The reception unit performs the normal processing on the reception side. The process of setting the received data as reception-determined data only when the received data has no bit error for a predetermined number of consecutive times and has the same value for a predetermined number of consecutive times. 7. The data communication device according to 5 or 6. 8. The reception unit, when an error has occurred in reception data from one of the first signal line and the second signal line continuously for a predetermined time, processes the other reception data. 8. The data communication device according to claim 5, wherein the data communication device executes a warning notification process.