JPH05101007A - Serial transmission equipment - Google Patents

Abstract

PURPOSE:To omit time and labor for setting by an operator and to prevent transmission abnormality from occurring due to the noncoincidence of transmission speed by automatically setting the transmission speed fitting in that of external equipment at the serial transmission equipment side. CONSTITUTION:A CPU 11 reads out first transmission speed from a ROM 12, and sends out an inquiry text from a serial transmission part 13 to the external equipment at the transmission speed. When a normal response is returned from the external equipment 2 via a serial transmission line, the CPU 11 fixes the transmission speed, and performs ordinary communication at the transmission speed. When no response is returned from the external equipment 2 or no normal response is returned, the CPU 11 reads out the transmission speed set next from the ROM 12, and sends out the inquiry text again from the serial transmission part 13 to the external equipment 2. Thereby, it is possible to always perform communication by selecting communication speed fitted in the transmission speed of the external equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is connected to an external device such as a programmable controller (PC) among process input / output devices used for process control, performs serial transmission, and fetches data of the external device into the controller. The present invention also relates to a serial transmission device that sends the data of the controller to an external device.

[0002]

2. Description of the Related Art Generally, of process input / output devices used for process control, serial data is transmitted by connecting to external devices such as PCs, data of external devices is taken into a controller, and data of controller is sent to an external device. The serial transmission system for sending out has the configuration shown in FIG. That is, the serial transmission device 1 and the external device 2
In order to transfer data between and, it is necessary to set the transmission speed, parity, character length, stop bits, etc.
The transmission rate is set individually by the switches of both the sialyl transmission device 1 and the external device 2. However, if the transmission rate setting is correct, that is, the switch between the serial transmission device 1 and the external device 2 is set. Transmission can be started if the settings according to are in agreement. If the settings of the switches between the two do not match, a transmission error will occur and transmission cannot be performed.

Therefore, when the transmission is started, the serial transmission device 1 transmits the data taken in from the external device 2 through the serial transmission line 3 through the transmission line 4 to the controller 5
On the contrary, the data of the controller 5 is received by the serial transmission device 1 through the same transmission line 4, and is sent to the external device 2 through the serial transmission line 3.

In such a general serial transmission system, in order to start the transmission, the transmission speed setting for each of the serial transmission device 1 and the external device 2 is performed as described above. The switches had to be set to match the transmissions.

[0005]

However, in such a conventional serial transmission system, as described above, by operating the switches for setting the transmission speed, which are individually provided in both the serial transmission device and the external device, respectively. Since the transmission rates had to be set to match, there were the following problems.

That is, in normal use, the switch for setting the transmission speed greatly differs in shape, mounting position, setting method, setting number, etc. depending on the model, and it takes time and effort for setting, and for beginners. It can be difficult to set. If the setting is incorrect, the transmission speed of the serial transmission device and the external device will not match, and a transmission error will occur, preventing normal serial transmission.However, if such a transmission error occurs However, it was not easy to determine that the cause was the mismatch of the set speeds.

The present invention has been made in view of the above-mentioned problems of the prior art, and is software when the serial transmission device side supplies power to an external device or when a command for selecting a transmission speed is input. By this means, the transmission rate on the serial transmission device side can be automatically selected according to the transmission rate of the external device, the labor of setting the transmission rate can be saved, and the occurrence of the transmission abnormality due to the mismatch of the transmission rates can be avoided. An object is to provide a serial transmission device.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a serial transmission device for connecting information to an external device having a serial transmission function through a serial transmission line and exchanging information by serial transmission, when the power is turned on or the transmission speed is selected. At the time of inputting a command, a transmission speed inquiring unit that outputs a transmission speed inquiry signal to the external device by changing the transmission speed, and a transmission speed by observing a response state from the external device to the inquiry signal output by the transmission speed inquiry unit The transmission rate change means for outputting the transmission rate change command to the transmission rate inquiring means when it is not suitable, and for outputting the instruction for fixing the transmission rate to the adapted transmission rate when it is suitable, and the transmission rate variable. Then, set the transmission rate to the compatible transmission rate output by the transmission rate determination means and perform serial transmission with the external device. Nau is that a serial transmission unit.

[0009]

In the serial transmission device of the present invention, when the power is turned on or the transmission speed selection command is input, the transmission speed inquiry means outputs the transmission speed inquiry signal to the external device while varying the transmission speed, and the transmission speed is transmitted. The response state from the external device to the inquiry signal is observed by the transmission rate judging means, and when there is no response or when there is a transmission abnormality such as response abnormality, a transmission rate change command is output to the transmission rate inquiry means and another The transmission speed inquiry signal of the transmission speed is output from the transmission speed inquiry means to the external device. If no transmission error occurs, it is determined that the transmission speed is suitable, and a command to fix the transmission speed is output. ..

Therefore, the serial transmission means receives the command of the adapted transmission rate from the transmission rate determination means, sets the transmission rate to the adapted transmission rate, and starts the serial transmission with the external device.

In this way, when performing serial transmission with an external device, a transmission speed that matches the serial transmission speed of the external device is automatically selected and serial transmission is executed at that transmission speed. ..

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.
5 shows a detailed internal configuration of the serial transmission device 1 in the general serial transmission system shown in FIG. This serial transmission device 1 is connected to an external device 2 via a serial transmission line 3 and is connected to a controller 5 shown in FIG. 4 via a transmission line 4, and a central processing unit (controlling the operation of the entire device ( CPU) 11,
A memory (RO for storing programs for arithmetic processing performed by the CPU 11 and other fixed data, parameters, etc.
M) 12, a serial transmission unit 13 that performs serial transmission with the external device 2 via the serial transmission line 3 according to the instruction of the CPU 11, and data transmission with the controller 5 via the transmission line 4 according to the instruction of the CPU 11. The transmission unit 14 for performing

Next, the operation of the above embodiment will be described.

FIG. 2 shows the flow of processing of the serial transmission device. The CPU 11 reads the first transmission speed from the ROM 12 when the power is turned on or a transmission speed selection command is input,
The inquiry text is sent from the serial transmission unit 13 to the external device 2 at the transmission speed (steps S1 and S2).

Therefore, when a normal response is returned from the external device 2 to the serial transmission unit 13 via the serial transmission line 3, the CPU 11 fixes the transmission speed and uses the serial transmission unit 13 to normalize the transmission speed. Communication is performed (steps S3 and S4).

However, if there is no response from the external device 2 to the inquiry text transmission or no normal response is returned, the CPU 11 causes the ROM 12
The next set transmission rate is read, and the inquiry text is sent again from the serial transmission unit 13 to the external device (steps S3, S5, S2).

In this way, the CPU 11 sequentially reads a plurality of transmission rates preset in the memory (ROM) 12 and gives them to the serial transmission section 13, and the inquiry text is transmitted to the external device 2 at each transmission rate. When a normal response is returned from the external device 2, the transmission speed is fixed and the serial transmission is performed at the transmission speed thereafter.

Here, as a method for judging the suitability of the transmission rate for the response to the inquiry text,
Even if the inquiry text is sent at the same transmission rate repeatedly for a certain period of time, if there is no response to it, it is judged that the transmission rates do not match, and the same processing is performed by changing to the next set transmission rate. If there is any response from the external device 2 to the inquiry text, it is the transmission speed of the external device 2 as it is. Therefore, after that, the transmission speed is fixed and serial transmission is performed. Further, the determination of suitability of the transmission rate is made by sequentially changing the transmission and inquiring until a response is returned from the external device or the transmission rate selection command from the outside is canceled.

In this way, even if the operator does not set the transmission rate on the side of the serial transmission apparatus, the apparatus itself can select and set the transmission rate according to the software program, and the controller or the operator can The serial transmission can be performed without considering the transmission speed of the external device 2.

The present invention is not limited to the above embodiment, and in a serial transmission device in which the parity is switched by a switch or the like, the parity can be automatically selected.

Generally, there are two methods of setting the transmission rate, that is, manual setting and automatic setting that the operator operates by himself. In the configuration in which these two methods are used in combination, the automatic transmission rate selecting function is used. As an application, as shown in the flowchart of FIG. 3, the transmission rate of serial transmission may be set in the following three cases to perform communication.

That is, a speed at which the transmission speed matches that of the external device is found by automatic selection (step S11),
Next, the transmission by automatic selection and the transmission speed by manual (MANUAL) selection are compared (step S12), and when the automatic setting and the manual setting match, normal transmission is started (step S13).

If the automatically set transmission rate and the manually set transmission rate do not match (steps S11 and S1).
2) Depending on the preset operation mode, the following A,
Select either B or C operation (step S1)
4, S15a-S15c).

A. The transmission is started at the automatically set speed, ignoring the manual setting (step S15a).

B warning (WARNING) is issued and transmission is started at the automatically set transmission speed (step S).
15b).

A C warning (WARNING) is issued, an instruction is issued to change the manual setting, and the automatic selection transmission speed is manually set (step S15).
c).

If this method is used, it is possible to detect a setting error in manual setting, and it is possible to detect an operation abnormality (for example, clock abnormality) due to a hardware trouble.

[0029]

As described above, according to the present invention, since the transmission rate is automatically set on the side of the serial transmission device so as to match the transmission rate of the external device, it is possible to prevent communication difficulties due to noise or the like. When the transmission speed needs to be reduced or the transmission speed needs to be increased to improve the performance, it is possible to automatically cope with it only by changing the transmission speed setting of the external device. In addition, since the setting is automatically performed by software, setting labor by an operator can be saved and setting mistakes can be reduced. Further, since the transmission abnormality caused by the disagreement of the transmission speed does not occur, it becomes easy to investigate the cause when the transmission abnormality occurs.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the above embodiment.

FIG. 3 is a flowchart showing a processing procedure of another embodiment of the present invention.

FIG. 4 is a system configuration diagram of a general serial transmission system.

[Explanation of symbols]

 1 Serial Transmission Device 2 External Equipment 3 Serial Transmission Line 4 Transmission Line 5 Controller 11 Arithmetic Processing Unit (CPU) 12 Memory (ROM) 13 Serial Transmission Unit 14 Transmission Unit

Claims (1)

[Claims] 1. A serial transmission device, which is connected to an external device having a serial transmission function through a serial transmission line and exchanges information by serial transmission, sets the transmission speed at power-on or when a transmission speed selection command is input. A transmission rate inquiry unit that outputs a transmission rate inquiry signal to the external device as a variable, and determines the appropriateness of the transmission rate by looking at the response state from the external device to the inquiry signal output by the transmission rate inquiry unit. Sometimes the transmission rate change command is output to the transmission rate inquiry means, and when the transmission rate determination means outputs a command to fix the transmission rate to the adapted transmission rate, the transmission rate is made variable and the transmission rate determination means Set the transmission speed to the compatible transmission speed to output and set the serial transmission means to perform serial transmission with external equipment. A serial transmission device provided.