JP2005159728A - Method for transmitting data - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission method for preventing an error from occurring in large-capacity and long-distance data transmission. <P>SOLUTION: Successive dummy data having an H or L level are added after real data, an accumulative potential accumulated at a transmission line when the real data are transmitted is reaccumulated to predetermined polarity according to the signal detection characteristics of a communication control IC. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a data transmission method of a data transmission circuit that performs large-capacity data transmission or long-distance transmission of a motion control system such as an NC or a robot.

Conventionally, a data transmission circuit is a balanced transmission system using a differential output type driver, a differential input type receiver, and a balanced circuit as a method for improving noise resistance and preventing transmission errors as in Patent Document 1. Is used.
In FIG. 1, reference numeral 11 denotes a data transmission circuit for performing data transmission / reception, and reference numeral 2 denotes a differential bus transceiver (hereinafter referred to as a transceiver) which is a transmission / reception interface unit, and includes a driver 3 and a receiver 4. Reference numeral 6 denotes a pair of differential signals (hereinafter referred to as transmission data) output from the transceiver 2, and the communication cable 7 connects between the data transmission circuit and at least one or more similar data transmission circuits. Is. Reference numeral 8 denotes a terminating resistor for adapting the characteristic impedance of a pair of electric wires, and is provided in the data transmission circuit at both ends of the communication cable 7. Reference numeral 1 denotes a communication control IC which outputs transmission data, inputs reception data, and outputs a transmission enable signal 5 for controlling the transceiver 2.
FIG. 4 shows a data waveform for one bit of the transmission data 6, and uses a coding method (hereinafter referred to as the Manchester coding method) that performs level inversion at the midpoint of the bits of the transmission data. In the Manchester encoding method, data is “0” when the first half of the data is “L” level and the second half is “H” level, and “1” when the first half is “H” level and the second half is “L” level. Therefore, the level is always inverted at the midpoint of the bit, so that the ideal waveform shown in FIG. 4 is ideally obtained, and the H level and L level pulses are equal. In the transmission line, the H level is a positive polarity and the L level is a negative polarity AC signal, and no DC component is generated in the transmission signal. However, in reality, characteristics such as rising characteristics and falling times of output data of the communication control IC 1 and the transceiver 2 vary, so that the output waveform is distorted as shown by the actual waveform in FIG. The distortion causes a bias in either the H level or the L level, and the bias generated for each bit during data transmission is accumulated. When the data transmission is completed and the driver 3 is turned off, the current flowing at the voltage generated by the above phenomenon is cut off, and thus a back electromotive voltage is generated by the L component included in the cable 7.
FIG. 5 shows a schematic diagram when the back electromotive force is generated. In general, an equivalent circuit of a cable can be represented by R, L, and C components, and the R, L, and C components increase as the cable length increases. Vdc in the figure represents the voltage generated by the above phenomenon, and the switch represents the output state of the driver 3. When the switch is ON, the driver 3 is enabled (during data transmission), and when the switch is OFF, the driver 3 is disabled. During data transmission, the switch is ON, and the current I flows at Vdc. When the data transmission is completed, the switch is turned off to interrupt the current, thereby generating a back electromotive voltage in the L component included in the cable.
FIG. 6 is a timing waveform showing waveforms of a transmission enable 5 signal, transmission data 6, and reception data during data transmission. When the amount of transmission data is small, the potential accumulated during data transmission is small, and the back electromotive voltage generated when the driver 3 is turned off is small. Further, when the cable length is short, the L component included in the cable 7 is small, so that the back electromotive voltage generated when the driver 3 is turned off is small. Since the counter electromotive voltage indicated by the one-dot chain line in FIG. 6 does not exceed the threshold voltage of the receiver 4, the receiver 4 does not detect erroneous data immediately after data transmission.
As described above, in the conventional data transmission method, during transmission of the data of the own station by the communication control IC 1, the transmission enable signal 5 is set to “1” and the driver 3 in the transceiver 2 is enabled to transmit the data. When the data transmission is completed, the transmission enable signal is set to “0”, the receiver 4 in the transceiver 2 is enabled, the received data is waited, and the reception operation is started when the carrier is detected.
Japanese Patent Laid-Open No. 06-85796

However, in the conventional data transmission circuit, since the receiver 4 is enabled and data reception is waited after the data transmission of the local station is completed, the driver is required when performing large-capacity data transmission or long-distance transmission. When 3 is turned off, a counter electromotive voltage exceeding the threshold voltage of the receiver 4 may be generated. FIG. 7 shows timing waveforms of a transmission enable 5 signal, transmission data 6 and reception data at the time of data transmission. Since the counter electromotive voltage indicated by the one-dot chain line exceeds the threshold voltage of the receiver 4, the receiver 4 detects erroneous data. The communication control IC 1 detects a carrier, determines that data is transmitted from another data transmission circuit, and starts a reception operation. However, there is a problem that a communication error occurs because data transmission is not started from other data transmission circuits.
The present invention has been made in view of such problems, and the back electromotive voltage due to the L component contained in the cable after data transmission is completed even during large-capacity data transmission or long-distance transmission. An object of the present invention is to provide a method for preventing the occurrence of a communication error by preventing the reception of erroneous data immediately after the completion of data transmission by preventing the voltage from being exceeded.

The present invention according to claim 1 is a receiver for detecting a transmission signal transmitted on a transmission line by an input signal from a receiving end connected to the transmission line, and a driver for transmitting the transmission signal on the transmission line. In a data transmission method of a data transmission circuit configured by a communication control IC that controls transmission / reception data, continuous H-level or L-level dummy data is added after the actual data, and is stored in the transmission line when the actual data is transmitted. Since the stored potential is re-accumulated to a predetermined polarity according to the signal detection characteristics of the communication control IC, erroneous data reception can be prevented immediately after the completion of data transmission, and communication errors can be prevented.
According to a second aspect of the present invention, there is provided a receiver for detecting a transmission signal transmitted on a transmission line by an input signal from a receiving end connected to the transmission line, and a driver for transmitting the transmission signal on the transmission line. In the data transmission method of the data transmission circuit configured by the communication control IC that controls the transmission / reception data, the bits of the actual data are set to a bit pattern biased to either the H level or the L level, Since the accumulated potential to be accumulated is accumulated in a predetermined polarity according to the signal detection characteristics of the communication control IC, it is possible to prevent erroneous data reception immediately after the completion of data transmission and to prevent the occurrence of a communication error.
According to the third aspect of the present invention, since the polarity of the dummy data is changed based on the carrier detection level of the communication control IC, it is possible to prevent erroneous data reception immediately after the completion of data transmission and to prevent the occurrence of a communication error.

  According to the data transmission method of the present invention, dummy data is added to actual data, and the potential accumulated in the transmission line during actual data transmission is changed to dummy data according to the signal detection characteristics of the communication control IC. Therefore, after the data transmission is completed, the back electromotive voltage generated by the accumulated potential can be prevented from exceeding the threshold voltage of the receiver, and the receiver can detect erroneous data after the data transmission is completed. Can be prevented. In addition, since the potential accumulated for each bit of transmission data can be set to a predetermined polarity, the back electromotive voltage generated by the accumulated potential after the completion of data transmission does not exceed the threshold voltage of the receiver. It is possible to prevent the receiver from detecting erroneous data after data transmission is completed.

  Hereinafter, specific examples of the method of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of a data transmission circuit that implements the data transmission system of the present invention, and uses the same circuit as the prior art circuit.

FIG. 2 is a timing waveform showing the data transmission waveform of the first embodiment. The method of the present invention will be described step by step with reference to this figure.
The transmission data is composed of actual data and additional data, and is transmitted with dummy data added after the actual data. The polarity of the dummy data needs to be changed according to the carrier detection level of the communication control IC 1. In the example of FIG. 1, since the communication control IC 1 detects the carrier at the “0” level, the potential accumulated after the completion of data transmission is made negative by making the additional data negative. The counter electromotive voltage generated when the transmission enable signal 5 is set to “0” and the receiver 4 is enabled after the data transmission is completed can be made positive, so that the threshold voltage of the receiver 4 is not exceeded. Therefore, it is possible to prevent the receiver 4 from detecting erroneous data. In this embodiment, since the carrier detection level is set to “0”, additional data with negative polarity is added after the actual data. However, in the case of a circuit that detects the carrier with “1”, the actual data is added after the actual data. The same effect can be obtained by adding positive additional data.

  FIG. 3 is a timing waveform showing the data transmission waveform of the second embodiment. By using a bit pattern in which each bit of transmission data is biased to a predetermined polarity instead of the midpoint of the data, the back electromotive voltage generated by the potential accumulated during data transmission is reduced by the receiver 4. It is possible not to exceed the threshold voltage. In the example of FIG. 1, since the communication control IC 1 detects the carrier at the “0” level, the potential accumulated in the data transmission after the completion of data transmission is set to the negative polarity by using a bit pattern in which each bit of the transmission data is biased to the negative polarity. Sexually. Since the back electromotive voltage generated when the transmission enable signal 5 is set to “0” after the data transmission is completed and the driver is turned off can be made positive, and the threshold voltage of the receiver 4 can be prevented from exceeding. The receiver 4 can be prevented from detecting erroneous data. In this embodiment, since the carrier detection level is set to “0”, transmission is performed with a bit pattern that is biased toward negative polarity. However, in the case of a circuit that detects a carrier at “1”, bias is toward negative polarity. The same effect can be obtained by performing transmission with such a bit pattern.

  Since the data transmission method is such that the potential accumulated during data transmission is biased to a predetermined polarity, it is possible to prevent receiving erroneous data due to the back electromotive voltage generated after data transmission. It can be applied not only to motion control systems such as, but also to data transmission applications such as large-capacity data transmission and long-distance transmission between cells and factories.

Block diagram of a data transmission circuit to which the method of the present invention is applied Waveform showing transmission data of the first method of the method of the present invention Waveform showing transmission data of the second method of the method of the present invention Waveform that expands 1 bit of conventional transmission data Block diagram explaining operation when back electromotive force is generated Waveform of each part explaining the operation at the time of conventional transmission data Waveform of each part explaining the operation when receiving data is erroneously detected

Explanation of symbols

1 Communication control IC
2 Transceiver 3 Driver 4 Receiver 5 Transmission enable signal 6 Transmission data 7 Cable 8 Termination resistor 11 Data transmission circuit

Claims (3)

A receiver connected to the transmission line for detecting a transmission signal transmitted on the transmission line according to an input signal from a receiving end, a driver for transmitting the transmission signal on the transmission line, and transmission / reception data are controlled. In a data transmission method of a data transmission circuit configured by a communication control IC,
A continuous H level or L level dummy data is added after the actual data, and the accumulated potential accumulated in the transmission line when the actual data is transmitted is determined according to the signal detection characteristic of the communication control IC. A data transmission method characterized by re-accumulating the data. A receiver connected to the transmission line for detecting a transmission signal transmitted on the transmission line according to an input signal from a receiving end, a driver for transmitting the transmission signal on the transmission line, and transmission / reception data are controlled. In a data transmission method of a data transmission circuit configured by a communication control IC,
The bits of the actual data have a bit pattern biased to either the H level or the L level, and the accumulated potential accumulated in the transmission line at the time of data transmission is determined in advance according to the signal detection characteristics of the communication control IC. A data transmission method characterized by accumulating in a certain polarity.   2. The data transmission method according to claim 1, wherein the polarity of the dummy data is changed based on a carrier frequency detection level of the communication control IC.

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