JPS5983431A - Method for controlling data transmission - Google Patents

Abstract

PURPOSE:To increase the data transmission efficiency and the line operating efficiency, by transmitting character data via the 1st transmission line and transmitting the same data to a transmission controller via the 2nd transmission line as return data at the terminal device side. CONSTITUTION:A transmission controller 13 consists of a main control section 13a, a line control section 13b and a hand shake section 13c. In transmitting a telegraphic message from the controller 13 to a terminal device 12 (12a-12c), the character data is transmitted sequentially one by one character via the 1st transmission line 14a. The terminal device 12 transmits the same data to the controller 13 via the 2nd transmission line 14b as the return data and the dissidence between the character data of one character transmitted from the controller 13 with the return data is detected. When the dissidence is detected, the data from the initial character data is retransmtted without completing the transmission of the remaining character data. A terminal controller 11 controls plural terminal devices 12a-12c.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a data transmission control method, and in particular improves processing in the case of data transmission abnormality when data is transmitted between at least one terminal device and a terminal control device. The present invention relates to a data transmission control method.

Description of Prior Art Conventionally, when data is transmitted between multiple terminal devices and a terminal control device, after all messages consisting of multiple character data are sent to the terminal device, the terminal device normally receives the message. When it determined that the request was made, it sent back an affirmative response (ACK), and when there was no response and a negative response (NAK) was sent back, it sent the message to the terminal device again. For this reason, the transmission procedure when the data transmission operation is normal has become complicated.

Furthermore, conventional data transmission methods perform error detection to detect data destruction due to noise or other various data transmission abnormalities. A known method for detecting this error is to add check bits (redundant bits) such as vertical and horizontal parity bits 1 to 1 after the message, and check for data transmission abnormalities on the terminal device side based on the test bits 1 to 1. It is being Therefore, the transmitted data includes redundant signals, resulting in a decrease in data transmission efficiency. In addition, the conventional method requires an arithmetic circuit to add vertical and horizontal paridi bits on the terminal control side, and an error detection circuit to perform parity checks on the terminal device side, resulting in a complicated circuit configuration. Along with this, there was a problem in that it took a long time from the start of message transmission until it was accurately transmitted to the other party, resulting in poor data transmission efficiency. Such a problem increases the cost accordingly if the data transmission line is a telephone line.

Furthermore, in the conventional method, even if an error occurs during the transmission of a message, the message cannot be retransmitted unless a negative response is received from the terminal device after all the messages set to be sent have been sent. As a result, unnecessary messages were sent after an error occurred, resulting in poor transmission efficiency and long data transmission times.

Purpose of the Invention Therefore, the purpose of the present invention is to eliminate the need for redundant bits in transmission data, improve data transmission efficiency, speed up processing when an abnormality occurs, and improve the efficiency of data transmission line usage. An object of the present invention is to provide a data transmission method.

Summary of the invention In summary, this invention is a transmission system! When sending a message from the II device to the terminal device, the character data is sent one character at a time through the first transmission line, and the terminal device side controls the transmission by using the same data as return data through the second transmission line. The transmission control device detects a mismatch between the transmitted one-character data and the returned data. When a mismatch is detected, the remaining character data of the message is retransmitted from the first character data without completing transmission, and when all the character data of the message has been transmitted without any abnormality, a response is received from the terminal device. This is a data transmission control method in which a data transmission operation is ended without waiting.

Effects of the Invention According to the present invention, there is no need for redundant bits such as check bits in transmission data, and there is no need for a special circuit for generating check bits used for error detection or a circuit for error detection. In addition to simplifying the circuit configuration,
Data transmission efficiency and data transmission line usage efficiency can be improved.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is an illustrative diagram showing an outline of a data transmission control system 1o which is the object 5- of the data transmission control method of the present invention.

FIG. 2 is a concrete block diagram of the data transmission system 1o.

With reference to FIGS. 1 and 2, data transmission system 10
The configuration of is explained. The terminal control device 11 controls a plurality of terminal devices 12a to 120 from a remote location. A transmission control device 13 is provided in relation to this terminal control device 11 . The transmission control device 1113 performs data transmission control between the terminal control device 1f11 and the plurality of terminal devices 128 to 120, and the main control unit 13a1
It includes a line control section 13b and a handshake section 13b. Although not shown, the main control unit 13a includes a microprocessor, a program storage memory (ROM), and a data storage memory (RAM).

line 11JII] unit 13b and each terminal device 112a to 1
2c, a data bus 14 including a first data transmission line 14a and a second data transmission line 14b is connected. The first data transmission line 1461a is used to transmit data from the transmission control device 14 to each terminal device 12a to 12C. The second data transmission line 14b is used to transmit data from the plurality of terminal devices 12a to 120 to the transmission control device 13. That is, in this embodiment, full-duplex communication (four-wire type) is used.

Here, the terminal devices 112a to 12C are, for example, a printer (12a shown in FIG. 1) or a console (12a shown in FIG. 1).
112b, 120), etc. The console includes a keyboard for entering data and a display device (such as a CRT display) for displaying data. However, the present invention is not limited to these terminal devices, and can be applied to various types of terminal devices. That is, in this invention, the device to be controlled when viewed from the upper level is called the old terminal device, and the device that controls the lower level, that is, the device on the higher level side, is called the terminal side m device.

The terminal control device 11 is then connected to a host processor or a center processor as necessary.

FIG. 3 is a schematic flow diagram for explaining the operation of one embodiment of the present invention.

FIG. 4 is a flowchart of a message transmission processing routine which is a feature of the present invention.

FIG. 5 is a flowchart of the message transmission/error detection subroutine. The programs shown in the flowcharts shown in FIGS. 3 to 5 are processed by the main control section 13a shown in FIG.

FIG. 6 shows transmission data and a time chart during data transmission to explain the operation of this embodiment.

Next, with reference to FIGS. 1 to 6, a specific embodiment of the data transmission method of the present invention and its operation will be described.

In step 1, initial processing is performed. This process includes clearing the storage WA area of the RAM included in the main control unit 13a.

Subsequently, in step 2, it is determined whether there is a message to be transmitted from the terminal control device 11 to any of the terminal devices @128 to 12C. Here, the transmitted message (so-called message) is one frame of data consisting of a plurality of character data. The presence or absence of this transmission message is determined, for example, when the terminal control device 11 stores the message in a transmission message storage area (not shown) and sets a transmission flag (not shown).
The main control unit 13a makes the determination based on whether or not the transmission flag is set. If it is determined that there is no transmitted message, it is determined in step 3 whether or not it can be received.

This determination is made by resetting the reception flag when the terminal control device 11 includes the reception flag and the area for storing the received message is empty. The main control unit 13a then determines the set state of the reception flag.

If it is determined that reception is not possible, step 2
Return to

In step 2 described above, if it is determined that there is a message to be transmitted, the process proceeds to step 4, where message transmission processing is performed. This message transmission processing operation is shown in detail in FIG.

Further, in step 3 described above, if it is determined that the message can be received, the process proceeds to step 9-5, where message reception processing is performed. This message reception processing operation is similar to the conventionally known processing, so
The details will be omitted.

Next, the specific operation of the message transmission process will be explained along the flowcharts shown in FIGS. 4 and 5.

In the message transmission process, there are cases where data is transmitted normally and cases where data is not transmitted normally (that is, cases where an abnormality occurs). Each case will be explained separately below.

(1) When the data is transmitted normally In step 6, the message reception command, that is, the timing code (ENQ) is sent to the line controller 13b and the data transmission line 1.
4a to the destination terminal device, or the message reception command and the identification data of the destination terminal device to which the message will be sent are commonly transmitted to a plurality of terminal devices. The terminal device that received this message reception command receives an acknowledgment code (A
CK) is transmitted to the main control section 13a via the data transmission line 14b1 line control section 13b. At this time, the main 10-control unit 13a repeats the operations of steps 7 and 8 and is on standby. That is, in step 7 it is determined whether or not a response has been received, and if it is determined that no response has been received, it is determined in step 8 whether or not a time has elapsed. If it is determined that the time has not exceeded, the process returns to step 7. Here, the determination of time over is made by determining whether a certain period of time, which is slightly longer than the time from when the transmission control device 13 sends the message reception command until the time when a response is received, has elapsed. If it is determined that a response has been received within a certain period of time, it is determined in step 9 whether or not the response reception data is an affirmative response.
If it is normal, it is an affirmative response, so step 10
Proceed to. In step 10, a flag (abbreviated as D-lower abnormality flag; not shown) included in the main control unit 13a and indicating that there is an abnormality is reset. Then the fifth
The message transmission/error detection subroutine shown in the figure is processed. Note that the operation steps of this message transmission/error detection subroutine are indicated by three-digit numbers.

In step 101, the starting address of the message, that is, the data to be transmitted to the terminal device, is set in the address register R1 included in the main control section 13A. In step 102, the number of characters in the message to be transmitted is set in a register R2 that stores the number of characters to be transmitted. Then, in step 103, data for one character is written to a transmission buffer register (not shown). When one character of data to be transmitted is written into this transmission buffer register, this data is sequentially transmitted in bit series to a desired terminal device via the data transmission line 14a by the line control section 13b. After writing the data for one character, the main control unit 13a saves the transmitted character data to the save register R3 in step 104. Thereafter, in step 105, the number of transmitted characters is subtracted by 1 by subtracting 1 from the contents of register R2. In step 106, it is determined whether the contents of register R2, ie, the number of characters to be transmitted, is O. However, from the moment the message starts to be sent until just before all the character data to be sent is completed,
Since the value of register R2 is not O, this is determined and the process proceeds to step 107. In step 107, 1 is added to the contents of the address register R1, and the read address of the memory storing the transmission data is incremented. In step 108, it is determined whether transmission of one character has been completed or not. If it is determined that one character has not been transmitted, it is determined in step 109 whether or not time has elapsed. If the time has not expired, the operations of steps 10B and 109 are repeated. When it is determined that transmission of one character has been completed, the next character data stored in the memory address designated by register R1 is transmitted in step 110.

Subsequently, in step 110, it is determined whether one character has been received. By the way, each time the terminal device to which the message was sent receives data for one character, it transmits the same data as the received character data to data transmission line 1.
4b to the egress side 13b for a line charge of 13-. For this reason, the main control unit 13a
If it is determined in step 111 that one character has not been received yet, in step 112 it is determined whether a certain period of time, which is slightly longer than the predetermined time required to receive one character, has elapsed, and one character is received within a certain period of time. It is waiting for the presence of received data, that is, the presence of return data from the terminal device. When one character data is received from the terminal device, the process advances to step 113. Step 1
13, it is determined whether or not the received character data (ie, returned data) currently received from the terminal device matches the previously transmitted transmitted character data saved in the register R3. If it is determined that the two match, the process proceeds to step 114. In step 114, the transmission character data transmitted in step 110 of the navigation is saved in register R3. In step 115, the contents of register R2 are decremented by 1, and the number of characters to be transmitted is decremented by 1. In step 116,
It is determined whether the value of register R2, ie, the number of transmitted characters 14-, is O. If it is determined that the value is not 0, the process proceeds to step 107. And steps 107-1
16 operations are repeated 1 fewer times than the number of characters sent.

Then, in step 116, when it is determined that the value of register R2 has become O, in other words, that all character data to be transmitted has been transmitted, step 11
Proceed to step 7. In step 117, it is determined whether one character has been received. If one character has not been received yet, it is determined in step 118 whether a certain period of time has elapsed, and if the certain period of time has not elapsed, the operations of steps 117 and 118 are repeated. Then, within a certain period of time, 1
When the character reception is completed, the process advances to step 119. In step 119, it is determined whether or not the previously transmitted character data and the received character data received this time match. If it is determined that they match, the process returns to step 11 shown in FIG.

In step 11, it is determined whether there is a data transmission abnormality. This determination is made based on whether or not the abnormality flag is set.

If the data is transmitted normally, the abnormality flag is not set, so the process advances to step 12. In step 12, an end-of-transmission code (E O'r ) indicating the end of data transmission is transmitted. In step 13, data indicating the end of transmission is given to the terminal control device 11, thereby terminating the data transmission operation with the one terminal device.

(2) Operation when there is an abnormality in the first data transmission, and the data transmission is normal the second time If any abnormality occurs in the message transmission/error detection subroutine described above, the following processing is performed. will be carried out.

That is, if a mismatch occurs between the transmitted character data and the received character data of a certain character while transmitting multiple character data of the message to be transmitted one character at a time, step 113 or 119 described above is performed. is detected, and an abnormality flag is set in step 120. Furthermore, if a certain period of time has elapsed in a state where one character has been received from the terminal device after transmitting one character data, this is detected in step 112 or 118, and an abnormality flag is flagged in step 120. is set. In this manner, if the abnormality flag is set due to some abnormality, it is detected in step 11 that there is an abnormality, and the process proceeds to step 14.

In step 14, it is determined whether this is the second time. This judgment is to judge whether or not it is the second time to perform the judgment operation of step 14 (pass through one step).

, Ll, but it is determined that this is not the second time, and the process proceeds to step 15. In step 15, a code is sent to the terminal device prompting for a response. Then step 1
In step 6, it is determined whether or not a response is received from the terminal device, and if no response is received, it is determined in step 17 whether or not a certain period of time has elapsed, and if the certain period of time has not elapsed, the operations of steps 16 and 17 are repeated. It will be done.

Then, a response is received from the terminal device within a certain period of time 17- If it is determined that there is, the process proceeds to step 18.

In step 18, it is determined whether the response from the terminal device is a negative acknowledgment code (NAK). Normally, if an abnormality occurs during data transmission, a negative acknowledgment code is sent from the terminal, and this is determined and the process proceeds to step 19.

In step 19, it is determined whether this is the second negative response. Initially, it is determined that this is not the second time, and the process returns to step 10.

Then step 10 above. Steps 101-119
The operation is repeated, and again 1 from the first character data of the message
Characters are sequentially transmitted to the terminal device. The noteworthy feature here is that when a message consisting of multiple character data is sent one character at a time, the sent characters and received characters are compared and matched to detect whether or not the transmission was successful. If this occurs, set the abnormality flag and then immediately resend the message starting from the first character data (in other words, retransmit) without continuing data transmission until the remaining character data has been transmitted.
It is to be. The reason for this is that if an error occurs during the transmission of 18-character data, unnecessary data transmission can be avoided by transmitting the remaining character data and immediately starting retransmission without waiting until the transmission is complete. , in order to increase data transmission efficiency.

When the second telegram 13 is transmitted normally, it is determined in step 11 that there is no abnormality, and the processes in steps 12 and 13 are performed.

(3) Operation when an abnormality occurs in two data transmissions If any abnormality occurs in the second data transmission, the abnormality flag is set in step 120 described above. Therefore, after the processing of the message transmission/error detection subroutine is completed, it is determined in step 11 that there is an abnormality again, and the process proceeds to step 14. In step 14, it is determined that there is a second abnormality, and the process proceeds to step 20. In step 20,
An end of transmission code (EOT) is sent to the terminal device.

In step 21, data indicating a non-response to the message (that is, there is an abnormality in which a message is sent but the terminal does not respond correctly) is given to the terminal control device 11;
Finish the operation.

(4) Operation when another abnormality occurs in the child If it is determined in step 8 above that no response has been received for a certain period of time after sending the message reception command, proceed to step 22. . In step 22, an end of transmission (EOT) is sent to the terminal. Step 23
After data indicating that there is no response is given to the terminal serial control device 11, the operation ends.

If a response is received within a certain period of time after transmitting the message reception command, and the response is not an informal response (ACK), this is determined in step 9, and step 24
Proceed to. In step 24, it is determined whether the response received data is a negative acknowledgment code (NAK). If it is determined that there is no negative response, the process returns to step 7. On the other hand, if the terminal device is unable to transmit data due to a failure or the like, it transmits a negative response in response to the message reception command. Therefore, if there is an abnormality in the terminal device, it is determined in step 24 that there is a negative response (NAK), and the process proceeds to step 25. In step 25, an end of transmission code (EOT) is sent to the terminal. ′
In step 26, data indicating that data transmission is not possible due to an abnormality in the terminal is provided to the terminal control device 11, and then the operation is terminated.

If it is determined in step 19 that there is a second negative response, the process proceeds to step 27. Step 2
At 7, an end of transmission code (EOT) is sent to the terminal. At step d3 in step 28, data indicating that data transmission cannot be performed normally due to an abnormality in the message is given to the terminal control device 11, and then the operation ends.

In this way, if an abnormality occurs during data transmission of any terminal device, if the data cannot be transmitted normally even though the message has been sent twice, or if there is an abnormality due to other reasons, After completing data transmission with one terminal device, data transmission with another terminal device is started.

If it is determined in step 109 that a time has elapsed (a certain period of time has elapsed) while transmitting one character, then the process proceeds to step 121 because the cause of the abnormality is on the transmission system t111 device 13 side.

Then, in step 121, after the transmission/reception prohibition process is performed, data transmission with all terminal devices is stopped.

[Brief explanation of the drawing]

FIG. 1 is an illustrative diagram showing an outline of a data transmission system to which the present invention is applied. FIG. 2 is a block diagram of the data transmission system. FIG. 3 is a schematic flow chart for explaining the operation of one embodiment of the present invention. FIG. 4 shows a 70-digit message transmission processing routine according to an embodiment of the present invention. FIG. 5 is a flowchart of the message transmission/error detection subroutine. FIG. 6 shows a time chart of the transmission message and the operating state during the data transmission period for explaining the present invention in detail. 22- In the figure, 10 is a data transmission system, 11 is a terminal control device, 128 to 12c are terminal devices, 13 is a transmission control device, 13a is a main control section, 13b is a line control section, 130 is a handshake section, and 14a is a a first data transmission line;
14b indicates a second data transmission line. Patent applicant: Tateishi Electric Co., Ltd. 23-

Claims (1)

[Scope of Claims] A data transmission system in which at least one terminal device is connected to a transmission control unit on a terminal control device side via a first data transmission line and a second data transmission line, wherein the transmission control device sequentially transmitting one character data of a message consisting of a plurality of character data to be transmitted to the terminal device via the first data transmission line; When receiving the transmitted one character data, transmitting the one character data as it is as return data to the transmission control device via the second data transmission line, the transmission control device transmitting the second data When the return data transmitted via the transmission line is received, detecting a mismatch between the return data and the transmitted one-character data corresponding to the return data; when the transmission IQ 111 device detects the mismatch, the message The step of retransmitting the message one character at a time starting from the first character data without completing the transmission of all the character data of the message, and the step of retransmitting the message one character at a time without completing the transmission of all the character data of the message, and when the transmission control device completes transmitting all the character data of the message, there is no data transmission abnormality. A data transmission control method comprising the step of bringing a data transmission operation to an end state without waiting for a response from the terminal device based on the above.