JPH08194650A - Serial communication method - Google Patents

Abstract

PURPOSE: To provide the serial communication method by which the response time of hespective terminals in an equipment connecting many terminals are made equal to each other. CONSTITUTION: In this serial communication method for serially collecting data by the equipment connecting many terminals through a signal line to one controller, the controller ordinarily repeatedly sends an inquiry command to all the terminals while successively circulating them, the designated terminal returns read data and the controller adds a signal showing whether the data received from the terminal are normally received or not to the next inquiry command and sends it to the terminal so that the response time of all the terminals can be averaged and shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial communication method for serially collecting data by a device in which a large number of terminals (slave units) are connected to one controller (slave unit) by signal lines. It is about.

[0002]

2. Description of the Related Art Conventionally, in a device in which a large number of terminals are connected to a single controller by a signal line, when the controller collects data from a large number of terminals, it is polled from the controller. It is usual to call predetermined terminals in order to collect data. Each terminal has a unique address. The controller sends a command for designating the address of a predetermined terminal through the signal line, and the corresponding terminal sends back data in response. Further, when the controller receives the data normally, it sends an ACK signal and completes.

If the data is not normally received, the controller sends a NACK signal, and the corresponding terminal repeatedly sends the data again. The controller repeats the above operation a specified number of times,
If the data cannot be received normally, it is treated as unreceivable and the data collection process from the next terminal is performed.

[0004]

However, when the number of terminals is large, as described above, the conventional polling method for collecting data is such that the first terminal collects data and the last terminal collects data. There is a large time difference in collection, and especially if there is a terminal on the way that has failed to send and receive data, the data collection of subsequent terminals will be delayed. Therefore, when used in a ticket reading device or the like for reading a ticket in a vehicle or the like to check the satisfaction of a train seat, there is a problem that the ticket reading process of the last seat is delayed and the response time becomes long. That is,
There was a problem that the response times differed depending on the seats, and it was not possible to provide equal service.

The present invention has been made in view of the above points, and an object of the present invention is to eliminate the above problems and to provide a serial communication method in which the response times of all terminals are substantially equal in a device to which a large number of terminals are connected. And

[0006]

In order to solve the above problems, the present invention provides a serial communication for serially collecting data by a device in which a large number of terminals are connected to one controller by signal lines. In the method, as shown in FIG. 1, the controller constantly circulates to all terminals in sequence and repeatedly sends an inquiry command, the designated terminal sends back the read data, and the controller sends the read data. With respect to the data received from the terminal, a signal indicating whether the data is normally received is attached to the next inquiry command and sent to the terminal.

[0007]

According to the present invention, as described above, the controller circulates to all terminals in order and repeatedly sends an inquiry command,
A signal indicating whether or not the data received from the terminal is normally received is sent with the next inquiry command.
It is possible to eliminate the repetition of command transmission / reception at one terminal as in the prior art, and to average and shorten the response time of all terminals.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 6 is a diagram showing a configuration example of a ticket reading device which employs the serial communication method of the present invention. In the figure, a terminal 1-1, a terminal 1-2, and a terminal 1-n are installed in each seat of a train car 1 or the like, and each terminal is provided with a controller 2 and a display unit 3 via a data transmission circuit 4. It is connected to the. The passenger reads the ticket for the reserved seat or the unreserved seat by operating each terminal. The controller 2 collects the data sent from each terminal and displays it on the display unit 3 and also sends a signal of the data reception to the terminal, and the terminal LE completes reading.
The D display (not shown) is turned on.

FIG. 7 is a diagram showing an example of the configuration of a balanced transmission circuit for connecting the controller and each terminal. As shown in the figure, the communication interface used in this device is RS485.
It is a serial interface. This is a balanced digital interface, suitable for long-distance, high-speed transmission, strong against data transmission under adverse conditions, and bidirectional with 32 drivers D and 32 receivers R. Can be transmitted. In the following description, the data communication speed is 19.2 KbP.
The case of S is shown.

FIG. 1 is a diagram showing a state of transmission and reception of a command representing the serial communication method of the present invention. FIG. 1A shows the case where the response time is the minimum, and FIG. 1B is the case where the response time is the maximum. Indicates. It will be described with reference to FIG. The terminal 1-1 is given a number of terminal number = 1 (ID = 1), and the terminal 1
The terminal numbers up to 18 are sequentially assigned to each terminal of -2 or less (the number of terminals is 18 in the figure). The controller 2 sequentially sends an inquiry command (described later) to each terminal according to the terminal number, and each terminal transmits a command with ticket data (described later) or a command without ticket data (described later) in response to the inquiry command. . The above operation is constantly repeated.

FIG. 1A shows a case where only the terminal 1-1 reads the ticket and immediately after that, an inquiry command is sent from the controller 2. The controller 2 sends the ticket data sent by the terminal 1-1. After going through each terminal for the attached command,
The inquiry command to be sent to the terminal 1-1 again is sent with a flag indicating whether or not the ticket data is normally received. Therefore, the response time of the terminal 1-1 (time until the command with ticket data is transmitted and a response is received from the controller 2) T = 13.84 + 6.87 × 17 + 2.04 = 1
It becomes 32.16 (msec).

FIG. 1B shows a case where the terminal 1-1 reads the ticket immediately after the inquiry command, and the other terminals simultaneously read the ticket. Response time T = 6.48 × 18 + 13.84 ×
It becomes 18 + 2.04 = 374.28 (msec). Therefore, any terminal can read the ticket and check
During 4.28 (msec), an LED display (not shown) indicating that the reading is completed can be turned on and confirmed. This difference in time is a time when the human senses feel almost equal, and all terminals can service almost equally.

FIG. 2 is a diagram showing the format of the inquiry command of the controller. As shown in the figure, the inquiry command consists of 4 bytes, and the inquiry code (EN
Q), terminal number, control flag, check digit (BC
It is transmitted in the order of C). An inquiry code (ENQ) is a code representing an inquiry command, a terminal number is a number for designating a terminal that receives a signal, and a control flag is a flag for turning on / off the seat and turning on / off a buzzer sound. It is composed of a flag or the like indicating whether or not the ticket data is normally received as described above. The check digit is a code for checking an error during transmission / reception.

FIGS. 3A and 3B are diagrams showing the format of the transmission command of the terminal. FIG. 3A shows the case where the ticket data is present, and FIG. 3B shows the case where the ticket data is not present. Figure 1 (A)
As shown in Fig.4, the transmission command of each terminal consists of 20 bytes (18 bytes in unreserved seats). From the beginning, an ACK code indicating a positive response, a terminal number, the number of digits of data, and ticket data (Fig. 4). (Refer to FIG. 3) and check digit (BCC).

The ACK code is an acknowledgment code indicating that the inquiry command from the controller 2 has been normally received.
The number of digits of data and data represents the number of digits of data read by each terminal. If the terminal does not read the ticket data and there is no data, the ACK code, the terminal number, and the data as shown in FIG.
A command consisting of 4 bytes of the check digit (BCC) and the number of digits of the data (= 0) is transmitted.

FIG. 4 is a diagram showing the format of the ticket data. Ticket data for reserved seats is the train number (2 bytes),
A 16-byte data consisting of a boarding date (4 bytes), a car number (3 bytes), a seat number (3 bytes), a section code (2 bytes for departure, 2 bytes for arrival), and a check digit (1 byte). It is The ticket data for unreserved seats is
The data consists of 14 bytes including a byte), a section code (2 bytes for the source and 2 bytes for the destination), a serial number (5 bytes), and a check digit (1 byte).

FIG. 5 is a diagram showing the response timing of the terminal representing the serial communication method of the present invention. The figure (A) shows the case where there is ticket data, and the figure (B) shows the case where there is no ticket data. The inquiry command transmitted from the controller 2 consists of 4 bytes and is transmitted over a time of 2.04 msec. Subsequently, the terminal designated by the terminal transmits a command consisting of 16 bytes (or 14 bytes) when there is ticket data, and the controller 2 further proceeds 11.80 msec after transmitting the inquiry command. Send an inquiry command to the terminal.

If there is no ticket data, the command transmitted by the terminal is 4 bytes, so the controller 2 transmits the inquiry command to the next terminal 4.80 msec after the transmission of the previous inquiry command. Between the controller 2 and each terminal, the exchange of the above-mentioned commands is constantly repeated in order to collect data.

As described above, the controller 2 sequentially circulates to all terminals and repeatedly sends the inquiry command, and the signal received from the terminals indicating whether or not the data is normally received is the next signal. Since the inquiry command is sent together with the inquiry command, the transmission and reception of the command is not repeated at one terminal as in the conventional case, so that the response time of all terminals can be averaged and shortened.

[0020]

As described in detail above, according to the present invention, the following excellent effects are expected. (1) The controller circulates to all terminals in sequence and repeatedly sends an inquiry command, and a signal indicating whether or not the data received from the terminal is normally received is sent to the next inquiry command. Therefore, it is possible to average and shorten the response time of all terminals, since the command transmission / reception is not repeated at one terminal as in the conventional case. (2) Further, the serial communication method of the present invention is effective for any device that handles a large number of terminals, and it is possible to improve the efficiency of online maintenance of a device in which a large number of terminals are connected online.

[Brief description of drawings]

FIG. 1 shows transmission and reception of a command representing a serial communication method of the present invention, and FIG.
FIG. 6B is a diagram showing a case where the response time is maximized.

FIG. 2 is a diagram showing a format of an inquiry command of a controller.

3A and 3B are diagrams showing the format of a transmission command of a terminal, FIG. 3A showing a case with ticket data, and FIG. 3B showing a case without ticket data.

FIG. 4 is a diagram showing a format of ticket data.

FIG. 5 shows the response timing of the terminal representing the serial communication method of the present invention. FIG. 5A shows the case where ticket data is present.
FIG. 3B is a diagram showing a case where there is no ticket data.

FIG. 6 is a diagram showing a configuration example of a ticket reading device adopting the serial communication method of the present invention.

FIG. 7 is a diagram showing an example of a balanced type transmission circuit connecting a controller and a terminal.

[Explanation of symbols]

 1 Vehicle 1-1 Terminal 1-2 Terminal 1-n Terminal 2 Controller 3 Display 4 Data Transmission Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G06F 17/40 H04L 29/04 29/08 H04L 13/00 307 Z

Claims (1)

[Claims] 1. A serial communication method for serially collecting data by a device in which a large number of terminals are connected to a single controller by a signal line, wherein the controller is always connected to all the terminals. The specified terminal sends back the read data, and the controller responds to the data received from the terminal by whether the data is normally received or not. A serial communication method characterized in that a signal is added to the next inquiry command and sent to the terminal.