JP2863066B2 - Data transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission method used in a data transmission system such as a multiplex transmission system for wiring reduction in a factory, a plant, and the like.
More specifically, the present invention relates to an improvement in a method for confirming whether or not transmission is normal on a transmission side.

[0002]

2. Description of the Related Art In a data transmission system, there is a case where a method of confirming whether or not transmission is normal on a transmission side is adopted in order to improve the reliability of transmission.

In such a case, conventionally, as shown in FIG. 6, for example, a transmission line other than the ground reference line 8 is transmitted between the transmission device 2 and the reception device 4 for transmitting a transmission signal including data. Two transmission lines 7 and a transmission line 7 for transmitting a reply signal are used, and a reply signal indicating that the reception was normal is returned from the receiving device 4 to the transmitting device 2 using the latter transmission line 7. Like that. This is a signal in which the conventional transmission signal and the reply signal are both generated by changing the voltage. When such two signals are put on one transmission line, the two signals affect each other and the waveform is distorted. This makes it impossible to identify both signals.

As a conventional communication frame structure, for example, as shown in FIG. 7, a reply confirmation period for confirming the return of a reply signal is provided separately from a synchronization period and a data transmission / input / output period. I have.

[0005]

However, in the conventional data transmission method as described above, there is a problem that the transmission time is lengthened and the transmission speed is reduced because the reply confirmation period must be provided.

Further, since the transmission line 7 for the reply signal must be provided, there is a problem that the number of transmission lines increases, and the material, the number of wiring steps and the cost increase.

Therefore, the present invention mainly provides a data transmission method which enables a transmission side to confirm whether or not transmission is normal, and also enables a reduction in the number of transmission lines and a reduction in transmission time. Aim.

[0008]

In order to achieve the above object, a data transmission method according to the present invention comprises a series of transmission signals including a start synchronization signal in a fixed state for synchronization and data subsequent thereto from a transmission side. Is transmitted cyclically in the voltage mode, and the receiving side transmits in the previous communication cycle.
Check whether the data reception was normal or abnormal.
Judgment is made for each communication cycle.
Even if the abnormality does not continue a predetermined number of times , during the transmission period of the start synchronization signal, a reply signal indicating that data reception in the previous communication cycle was normal is transmitted to the transmission signal. Using the same transmission line that sends
Return to the transmitting side in the current mode
If it continues more than once, return the reply signal to the sender.
It is characterized by not having.

[0009]

According to the above method, the transmission side can confirm whether or not the transmission is normal based on the presence or absence of the reply signal.

Further, the transmission signal is transmitted in the voltage mode,
Since the reply signal is returned in the current mode, both signals can be identified even if both signals are put on one transmission line, so that one transmission line can be shared for transmission of both signals. As a result, the number of transmission lines can be reduced.

Since the reply signal is returned at the same timing as the start synchronization signal, a special period for returning the reply signal is not required. As a result, the transmission time can be reduced.

[0012]

FIG. 1 is a diagram showing an example of a transmission signal waveform and a reply signal waveform used in a data transmission method according to the present invention.

In this embodiment, as shown in FIG. 1, a start synchronizing signal for synchronization and data 0
To n are cyclically transmitted from the transmitting side in the voltage mode. After the last data n, there is provided an I / O service period for processing the next input on the transmitting side and processing the output on the receiving side. T is a period for one unit, for example, 120 μs.

[0014] Then, during the transmission period of the start synchronization signal, the receiving side returns a reply signal RS indicating that data reception in the immediately preceding communication cycle was normal to the transmitting side in the current mode. I have to. The pulse width of the reply signal RS is, for example, T described above.
The transmission side can confirm whether or not the transmission is normal based on the presence or absence of the reply signal.

The return of the reply signal RS in the current mode from the receiving side can be easily performed, for example, by consuming more current than usual in the transmission line on the receiving side during the transmission period of the start synchronization signal. Can be done.
An example of the specific method will be described later in detail with reference to FIG.

According to the above data transmission method, the transmission signal TS is transmitted in the voltage mode and the reply signal RS is returned in the current mode. Therefore, even if both signals are put on one transmission line, the two signals can be identified. Therefore, one transmission line can be shared for transmission of both signals. As a result, the number of transmission lines can be reduced.

FIG. 2 shows a schematic example of a data transmission system using the above data transmission method.
Between the receiver 2 and the receiver 14, only one transmission line 16 other than the ground reference line 18 is required.

As described above, according to the data transmission method,
The transmission side can confirm whether or not the transmission is normal by the presence or absence of the reply signal RS, so that the reliability of the transmission is improved and the transmission line dedicated to the reply signal is not required. Wiring man-hours and cost savings can be realized.

Further, in the above data transmission method, the reply signal RS is returned at the same timing as the start synchronization signal, so that a special period for returning the reply signal is not required. As a result, the transmission time can be reduced, and the transmission speed can be improved.

Incidentally, a method of expressing data in the transmission signal TS in FIG. 1 will be described for reference. In this example, whether the data is "0" or "1" depends on the pulse width (that is, by pulse width modulation). Is to be expressed. More specifically, a combination of an “L” level of 30 μs and a subsequent “H” level of 90 μs represents “0”, and a combination of an “L” level of 60 μs and a subsequent “H” level of 60 μs represents “1”. ". One cycle is T described above and is 120 μs. The use of such pulse width modulation is less susceptible to disturbances due to noise, power supply voltage fluctuations, and the like, as compared to a method of simply expressing “0” or “1” based on the presence or absence of a pulse. Is further improved.

Further, in this example, when one "0" or "1" data is transmitted, the data and the complementary data whose value is inverted are transmitted continuously as a set. . In this way, on the receiving side,
Each time one "0" or "1" data and the following complementary data are received, the complementarity between both data is checked (that is, if one is "0", the other is "1") By doing so, transmission errors can be detected reliably and promptly, and in this sense, transmission reliability is further improved.

Needless to say, the use of the above-described data representation method is not essential to the present invention.

FIG. 3 is a diagram showing a more specific configuration example of the data transmission system of FIG.

In this example, the transmission device 12 includes the input circuit 2
0, output circuit 30, transmission control circuit 2 connected to them
2, a changeover switch 24 controlled by the transmission control circuit 22, a power supply terminal 32, a resistor 26 connected between the changeover switch 24, and an amplifier 28 whose input section is connected to both ends of the resistor 26. Changeover switch 24
The reference line 18 is connected to one terminal b, and the transmission line 16 is connected to the common terminal c.

In this example, the receiver 14 has an input section connected to an amplifier 44 connected to the transmission line 16 and the reference line 18, a reception control circuit 42 connected to the amplifier 44, and to the reception control circuit 42. An output circuit 40 is provided.
Further, a resistor 46 and a transistor 48 connected in series with each other are connected in parallel between the transmission line 16 and the reference line 18. 52 is a power supply terminal. This power terminal 52
The power supply terminal 32 may be connected to another power supply or a common power supply.

The input circuit 20 in the transmission device 12 is a circuit for an input interface, and in this example, an on / off signal at (n + 1) points is input. The output circuit 30 is a circuit for an output interface for outputting an alarm described later.

The main function of the transmission control circuit 22 is to convert data supplied in parallel from the input circuit 20 into serial data, and to convert the data into complementary data,
A start synchronization signal and an I / O service period are added to the signal S as a source of the transmission signal TS as shown in FIG.
Has the ability to create _one .

The changeover switch 24 is connected to the transmission control circuit 2
In response to the signals S ₁ from 2, switching the common terminal c to the terminal a and the terminal b side. When the terminal is switched to the terminal a side, a voltage is applied from the power supply terminal 32 via the resistor 26, so that the voltage of the common terminal c becomes "H" level. When the terminal is switched to the terminal b side, the common terminal c is connected to the ground. Becomes "L" level. In this manner, the changeover switch 24 controls the transmission line 16 under the control of the transmission control circuit 22.
Then, the transmission signal TS as shown in FIG. 1 is output in the voltage mode. The changeover switch 24 is constituted by, for example, a combination of a plurality of transistors.

The amplifier 44 in the receiver 14 is connected to the transmission line 1
6, and amplifies the transmission signal TS transmitted thereto and supplies it to the reception control circuit 42.

The reception control circuit 42 has the following two main functions in this example. The serial data in the transmission signal supplied from the amplifier 44 is converted into parallel data to generate output data, and the output data is supplied to the output circuit 40.
The output circuit 40 outputs outputs 0 to n based on the output data. Reception of data for one communication cycle is determined whether or not normal, when was normal, during the reception period of the start synchronization signal in the next communication cycle, and outputs a signal S ₂ to turn on the transistor 48 . If not, an alarm is output via the output circuit 40.

Here, the normal reception of data in one communication cycle means, for example, that the transmission signal TS is not disturbed and the basic frame as shown in FIG. This means that the complementarity with the complementary data is all established.

When the transistor 48 is turned on during the reception period of the start synchronization signal (from the transmission side, during the transmission period of the start synchronization signal by switching the changeover switch 24 to the terminal a), the transmission line 16 and the reference line 18 Is connected to the power supply terminal 32 on the receiving side.
6. In the path of the changeover switch 24, the transmission line 16, and the resistor 46, a current larger than usual (for example, about 10 times the usual current) flows. This current is the above-mentioned current mode reply signal RS, and thus the receiving device 1
4 can return the reply signal RS to the transmitting device 12 in the current mode.

The increase in the transmitting apparatus 12, the voltages V ₁ across the resistor 26 is monitored by the transmission control circuit 22 via the amplifier 28, than the voltage V ₁ is normal during the transmission period of the start synchronization signal If this is the case (this means that a large amount of current flows through the resistor 26 and the reply signal RS is returned), it is determined that the transmission in the previous communication cycle was normal, and the voltage V ₁ must rise. If it is determined to be abnormal, an alarm is output via the output circuit 30.

An example of a more specific processing flow in the transmitting device 12 and the receiving device 14 is shown in FIGS.
Are shown below. As can be seen from FIG. 5, in this example,
An alarm is not output immediately upon one reception error, but an alarm is output only when reception is abnormal three or more times consecutively. In this case, an alarm is not issued in the case of a momentary communication abnormality, so that it is easy to use in an actual site.

[0035]

As described above, according to the present invention, it is possible to confirm on the transmitting side whether or not the transmission was normal based on the presence or absence of the reply signal, so that the reliability of the transmission is improved and the exclusive use of the reply signal is achieved. This eliminates the need for the transmission line, thus realizing reduced wiring, reduced wiring man-hours, and reduced cost.

Further, in the data transmission method of the present invention, since the reply signal is returned at the same timing as the start synchronization signal, a special period for returning the reply signal is not required. As a result, the transmission time can be reduced, and the transmission speed can be improved. In addition, one reception error
Do not stop returning the reply signal immediately
If the reception is abnormal for more than one consecutive
Since the return of the ply signal is stopped,
It is not necessary to issue an alarm when a communication error occurs
Easy to use in actual factories and plants
It has a large practical effect.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a transmission signal waveform and a reply signal waveform used in a data transmission method according to the present invention.

FIG. 2 is a schematic diagram showing an example of a data transmission system using the data transmission method according to the present invention.

FIG. 3 is a diagram showing a more specific configuration example of the data transmission system of FIG. 2;

FIG. 4 is a diagram illustrating an example of a processing flow on the transmission device side.

FIG. 5 is a diagram illustrating an example of a processing flow on the receiving device side.

FIG. 6 is a schematic diagram illustrating an example of a conventional data transmission system.

FIG. 7 is a schematic diagram showing an example of a frame configuration in a conventional data transmission method.

[Explanation of symbols]

 12 Transmitter 14 Receiver 16 Transmission line 18 Reference line

Continuation of the front page (56) References JP-A-4-104535 (JP, A) JP-A-3-285429 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 1 / 14 H04L 5/22 H04L 25/02

Claims (1)

(57) [Claims] In a data transmission system, a series of transmission signals including a start synchronization signal in a fixed state for synchronization and subsequent data are cyclically transmitted in a voltage mode from a transmission side . Previous communication site
The reception of data in the vehicle was normal or abnormal.
Is determined for each communication cycle, and if normal,
And if the abnormality does not continue multiple times as specified
In this case , during the transmission period of the start synchronization signal, a reply signal indicating that data reception in the immediately preceding communication cycle was normal is transmitted in the same transmission as the transmission signal.
Return to the transmitting side in current mode using the transmission line,
Sends the reply signal if it has continued more than a predetermined number of times
A data transmission method characterized in that the data is not returned to the side .