JPH04348444A - Data transfer device - Google Patents

Abstract

PURPOSE:To surely transfer the data to the distant side with no influence of a communication error, etc. CONSTITUTION:A data transfer device is provided with a counter value adding means 16 which addes the counted-up or counted-down value to the transferred new data at the data transmission side 1 together with a signal transmission means 14 whith transmits the data and the counter value in a fixed cycle by the scan communication. A transfer confirming means 17 compares the data sent back from the data reception side 2 with the counter value and the data under transfer with the counter value respectively. When the coincidence is confirmed in the comparison, the means 17 sends the new data and the counted-up or counted-down value to the reception side 2. If no coincidence is confirmed, the means 17 instructs the means 14 to continuously send the data under transfer and the counter value. Furthermore the side 2 is provided with a data transfer confirming means 25 which detects a fact that the count value of the received signals is different from the count value received precedently and confirms the start of the transfer of data and a signal return means 26 which returns the data and the counter value received from the side 1 in a fixed cycle by the scan communication.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a data transfer device for periodically transferring data between one communication station and another communication station by scan communication. The present invention relates to a data transfer device that is applied to a system that transfers general-purpose data at regular intervals.

0002

[Prior Art] Conventionally, field control
In a distributed control system consisting of a station and multiple input/output devices (process I/O devices) connected via a communication bus, scan transmission (cyclic transmission) is used as one of the input/output data transmission procedures. method is adopted. FIG. 3 is a conceptual diagram for explaining the scan transmission method. In this figure, 1 is a control calculation unit (field
A control station (2) is a plurality of input/output devices, which input process signals from a sensor group 3 installed in the field, and send operation signals to operation ends such as valves 4. The control arithmetic device 1 and the input/output device 2 transmit their own data to each other at regular intervals, and the operation thereof is as follows. Scan input data (data input from various sensors 3) possessed by the input/output device 2 is transmitted to the control calculation device 1 at regular intervals and written to a corresponding area in the scan input image (memory) 11. The written input data is updated by the input data sent in the next cycle. Output data from the control calculation device 1 to the input/output device 2 is written in the corresponding area of the scan output image (memory) 12,
It is transmitted to the input/output device 2 at regular intervals. In the control calculation device 1, for example, when the CPU uses data from the input/output device 2, the data is stored in the scan input image 11 without being aware of the communication between the control calculation device 1 and the input/output device 2. It is sufficient to read and use the data written in the corresponding area. Also, when sending data to the input/output device 2 side, the output data can be written in the scan output image 12 without being aware of communication between the control calculation device 1 and the input/output device 2.

0003

[Problems to be Solved by the Invention] Conventionally, in the above-described scan transmission method applied to distributed control systems, the side that uses the transmitted data is connected to the control arithmetic unit 1 and the input/output device 2. Although it is convenient to be able to easily handle data without being aware of the communication between them, it is difficult to reliably transfer a certain amount of data. Here, "certain" means
Loss of communication frame due to communication error, control calculation unit 1
This means that data can be transmitted without missing or duplicating information even if there are variations in the timing of accessing scanned input/output images within the system. The present invention has been made in view of these points, and an object of the present invention is to provide a data transfer device that can reliably transfer data from a data sending side to a data receiving side.

0004

[Means for Solving the Problems] The present invention, which achieves the above object, is a data transfer device that performs data transfer at regular intervals between one communication station and another communication station by scan communication. On the data sending side, there is a counter value addition means for adding a counter value that is counted up or down when new data is transmitted to the sending data, and the sending data and the counter value are sent out at a constant cycle by scan communication. The signal sending means compares the data returned from the data receiving side with the counter value, and the data currently being sent with the counter value, and compares the returned data with the counter value and the data currently being sent with the counter value. If they match, the signal sending means is instructed to send new data and the incremented or decremented counter value to the receiving side, and if they do not match, it instructs the signal sending means to continue sending the data and counter value currently being sent. data transfer recognition means for detecting that the counter value of the received signal is different from the previously received counter value and recognizing that the data transfer has started; The present invention is characterized in that it is provided with a signal return means for returning the data and counter value sent from the data transmitting side at a constant cycle by scan communication.

[0005]

[Operation] A counter is provided on the data sending side, and each time new data is sent, the counter value is counted up or down. The counter value adding means adds the counter value of the counter to the data sent out at regular intervals and sends the data to the other party. On the data receiving side, a counter value is extracted from the received signal, and if the counter value has changed from the previous counter value, it is recognized that new data transfer has started. Moreover, when data is received, the received data and the counter value are returned to the transmitting side. The transfer confirmation means on the data sending side compares the returned data with the counter value and the data currently being sent with the counter value, and if they match, the new data and the counted up or down counter value are compared. The signal is sent to the receiving side, and if there is a mismatch, the signal sending means is instructed to continue sending the data currently being sent and the counter value. This enables reliable data transfer while handshaking between the data sending side and the data receiving side.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a data transmitting side, 2 is a data receiving side, and the two are connected by a communication line 3. Note that this example assumes a configuration in which data is transferred from one side to the other, but when performing bidirectional data transfer, it is necessary to have a sending function and a receiving function in one device. Be prepared.

On the data sending side 1, 11 is a scan image memory storing a scan image of the sending data, 12 is a microprocessor for realizing various functions, and 13 is a communication interface, which are connected via an internal bus. connected to each other. 14 is a signal sending means for sending the data stored in the scan image memory 11 at the scan communication cycle; 15 is a counter that is counted up or down when sending new data; and 16 is a counter value of this counter. This is a counter value adding means to be added to the sending data. Reference numeral 17 denotes a transfer confirmation means for comparing the data returned from the data receiving side 2 with the counter value and the data currently being sent with the counter value to confirm whether the data transfer has been performed reliably. If the returned data and the counter value match, and the data currently being sent and the counter value match, the transfer confirmation means 17 determines that the data transfer has been reliably performed, and counts up or down with new data. The signal sending means instructs the receiving side to send the data and the counter value that are currently being sent to the receiving side, and if they do not match, it is determined that the data transfer is not reliably performed, and the signal sending means continues to send the data and the counter value that are currently being sent. It is configured to instruct. Note that the microprocessor 12 implements each means such as the signal sending means 14, the counter 15, the counter value addition means 16, and the transfer confirmation means 17 by software.

On the data receiving side 2, 21 is a scan image memory in which the transferred scan image data is stored, 22 is a microprocessor, and 23 is a communication interface, which are connected to each other via an internal bus. 24 is a counter value extracting means for extracting a counter value from the received signal; 25 is a counter value extracting means for extracting a counter value from the received signal; and 25, when it is detected that the current counter value extracted by the counter extracting means 24 is different from the previously received counter value, the data is extracted. When the data transfer recognition means 26 receives the data and counter value sent from the data sending side 1, the data transfer recognition means 26 recognizes that the transfer has started, and returns the received data and the counter value at a constant cycle through scan communication. This is a signal return means. Note that the microprocessor 22 implements a counter value extraction means 24, a data transfer recognition means 25, a signal return means 26, and the like using software. The operation of the apparatus configured in this way will be explained next.

FIG. 2 shows data sending side 1 and data receiving side 2.
3 is a time chart showing the operation of scan communication performed by. Here, it is assumed that data "A" to "E" are transferred from the transmitting side to the receiving side. Note that the time axis is provided from the top to the bottom of the page. first,
On the sending side 1, the signal sending means 14 and the counter value adding means 16 add a new counter value "0" to the data "A" to be transferred and use scan communication to start transferring the data "A". Send. In this data transfer operation, the same data "A" and the counter value "0" are sent every scan communication cycle until the next step.
It continues to repeatedly send a communication frame consisting of .

[0010] On the receiving side 2, counter value extraction means 2
4 extracts the counter value from the received signal, and if the extracted counter value has changed from the previous value, the data transfer recognition means 25 determines that the transfer of new data has started, and the data transfer recognition means 25 determines that the transfer of new data has started, The obtained data "A" is stored in a predetermined area of the memory 27 and made available to the microprocessor 22. Upon receiving the data, the signal return means 26 sends the received data "A" and the counter value "0",
It is sent back to the sending side at regular intervals using scan communication. In such an operation, the same data and counter value continue to be sent every scan communication cycle until proceeding to the next step.

[0011] On the data sending side 1, the transfer confirmation means receives the data "A" and the counter value "0" sent back from the data receiving side by scan communication, and checks the received data, the counter value, and the current data being sent. Compare the data with the counter value. If they match, it is determined that the data has been transferred correctly, and the new data "B" and, for example, the incremented counter value "1" are added.
The signal sending means 14 is instructed to send the following to the receiving side. Upon receiving such an instruction, the signal sending means 14 enters a new step and sends new data "B" and counter value "
1" to the receiving side. If there is a mismatch between the received data and the counter value, or the data currently being sent and the counter value due to a communication failure such as a loss of a communication frame, the currently sent data "A" and the counter value "0" will continue to be sent. instructs the signal sending means to do so. In this way, the sending side and the receiving side reliably transfer data "A", "B", etc. while handshaking. In the above description, the counter value is counted up, but it may be counted down. Further, here, it is assumed that the counter includes a counter such as a register means, in which a digital value held therein changes depending on an input signal applied thereto.

0012

As described in detail above, according to the present invention, it is possible to realize a data transfer device that can reliably transfer various types of data to the other party without being affected by communication errors.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention.

FIG. 2 is a time chart showing the operation of scan communication performed between a sending side and a receiving side.

FIG. 3 is a conceptual diagram for explaining a scan transmission method.

[Explanation of symbols]

1 Data transmission side device 2 Data receiving side device 3 Communication line 11 Scan image memory 12 Microprocessor 13 Communication interface 14 Signal sending means 15 Counter 16 Counter value addition means 17 Transfer confirmation means 21 Scan image memory 22 Microprocessor 23 Communication interface 24 Counter value extraction means 25 Data transfer recognition means 26 Signal return means

Claims (1)

[Claims] Claim 1: A data transfer device that performs data transfer at regular intervals between one communication station and another communication station by scan communication, wherein the data transmission side includes a count when new data is transmitted. counter value adding means for adding a counter value to be raised or lowered to the sending data;
A signal sending means that sends the data to be sent and a counter value at a constant cycle by scan communication, and a signal sending means that compares the data and counter value returned from the data receiving side with the data currently being sent and the counter value, and sends it back. If the received data and the counter value match, and the data currently being sent and the counter value match, the new data and the counted up or down counter value are sent to the receiving side, and if they do not match, the data currently being sent is Transfer confirmation means is provided to instruct the signal sending means to continue sending the data and the counter value, and the data receiving side detects that the counter value of the received signal is different from the previously received counter value. The present invention is characterized in that it is provided with a data transfer recognition means for recognizing that data transfer has started, and a signal return means for returning the data and counter value sent from the data transmission side at regular intervals by scan communication. data transfer equipment.