JP2902411B2 - Data transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Industrial applications]

The present invention relates to a multi-drop data transmission device based on the RS485 standard in which a master station and a plurality of slave stations are connected via a transmission line.

[Prior art]

Conventionally, as a serial data transmission method in a factory or an office, when a master station and a slave station are in one-to-one correspondence,
In many cases, a data transmission method based on the RS232C standard or the RS422 standard is adopted. When the number of the master station and the slave station is one-to-many, based on the RS485 standard, as shown in FIG. A number of slave stations S _{1 to} S _n are connected to one transmission line l connected to
Many multi-drop systems are used to connect.
In a multi-drop method, connect the transmission line l to the master station M slave station S _1, and so on to connect the transmission line l to Tsuginiko station S ₁ slave station S _2, sequentially sends the transmission line l wiring It is usual to do.

[Problems to be solved by the invention]

The above-mentioned conventional arrangement, since sequentially feeding wiring between the transmission line l child station S ₁ to S _n, for example, as shown in FIG. 7, the first floor from the third floor, respectively slave station S ₁ to S until _n is arranged, when the location of the slave station S ₁ to S _n in the wiring location and each floor of the transmission line l between each floor such that apart, each slave station S ₁ transmission line l to S Wiring must be performed in such a manner that the wiring is folded back at _n , so that there is a problem that the transmission line 1 becomes long and wiring work is troublesome. The present invention is aimed at solving the above problems,
It is an object of the present invention to provide a data transmission device capable of connecting a master station and each slave station via individual transmission lines.

[Means for Solving the Problems]

According to the present invention, in order to achieve the above object, in a multi-drop data transmission device based on the RS485 standard in which a master station and a plurality of slave stations are connected via a transmission line, a signal is transmitted between each slave station. A plurality of interfaces comprising a driver / receiver connected in parallel to the controller, an operation selection switch for turning on / off the operation of each interface, and a plurality of terminals for connecting slave stations to each interface, The master station is provided with a plurality of resistance connection switches for selecting a state in which a terminating resistor is connected to each terminal and a state in which the terminal resistance is disconnected. The resistance connection switch is provided with a second contact connected to the controller. By opening and closing, the connection and non-connection of the terminating resistor can be recognized by the controller.

[Action]

According to the above configuration, a plurality of interfaces are connected to the controller in parallel, and each interface is provided with a terminal. If a slave station is connected to each terminal, the plurality of slave stations can be connected via individual transmission lines. Will be able to connect. In addition, a plurality of resistance connection switches are provided for selecting a state of connecting and disconnecting a terminating resistor to a terminal connecting a slave station to each interface, and an operation selection switch is provided so that operation of each interface can be turned on / off. Therefore, each interface of the master station can be set to be terminated, or only the required number of interfaces can be operated. In addition, since the resistor connection switch is provided with the second contact and the controller can recognize the connection and disconnection of the termination resistor by the resistance connection switch, the controller recognizes whether the termination resistor is connected for each interface. It is possible to determine the presence or absence of an erroneous setting by integrating the state of the second contact and the impedance of the transmission line. Further, since it is possible to connect a plurality of slave stations to one interface by sending wiring as in the conventional case, it is possible to use together with the wiring method described in the prior art, and to suit the construction site. The most suitable wiring method can be adopted.

【Example】

FIG. 2 shows a basic circuit of a main part of the master station M, and FIG. 3 shows a specific circuit. In the following embodiment, the master station M is connected to the transmission line l.
An example is shown in which two sets of terminals T ₁ and T ₂ are provided for connecting. The master station M is provided with a controller 1 for exchanging signals and exchanging various data with the slave stations S ₁ and S _2.
Is provided with a transmission terminal Tx for outputting a signal and a reception terminal Rx for receiving a signal. The controller 1 has two interfaces, a driver 2a and a receiver 2b.
2 ₁ and 2 ₂ are connected. A protection circuit 3 is provided at an input terminal of the receiver 2b, and an input terminal of the protection circuit 3 is commonly connected to an output terminal of the driver 2a and to terminals T ₁ and T ₂ . That is, the respective interfaces 2 _1, 2 respectively every ₂ to terminal T _1, T ₂ is provided. Between the _two poles of each terminal T ₁ and T ₂ , the first contact r of the resistance connection switch SW ₁ and SW ₂ respectively
Terminal resistors R ₁ and R ₂ are inserted through ₁₁ and r ₂₁ . Each of the terminating resistors R ₁ and R ₂ is set to a value corresponding to the impedance of one terminal station as a terminal station. Each terminal T ₁ , T ₂ can be connected to up to two terminal stations at the end. That is, when the resistance connection switches SW ₁ and SW ₂ are turned on, the terminal T
_1, the T ₂ becomes a slave station that terminates can connect only one station. The resistance connection switches SW ₁ and SW ₂ are provided with second contacts r ₁₂ and r ₂₂ connected to the controller 1, so that the on / off state of the resistance connection switches SW ₁ and SW ₂ can be recognized by the controller 1. ing. Output of one of the interface 2 ₁ receiver 2b is connected to one input terminal of the gate 4 composed of two-input AND circuit, the other interfaces 2 ₂
The output of the receiver 2b is connected to the other input terminal of the gate 4 through the first contact point r ₀₁ of the operation selection switch SW _0. Therefore, when the operation selection switch SW ₀ is on, both interfaces 2 _1, the output of the 2 ₂ receiver 2b are input to the controller 1 via the gate 4, both interfaces 2 _1, 2 ₂ slave station corresponding to S _1, it becomes possible to transfer the signal to the S _2. On the other hand, if turning off the operation selection switch SW _0, thereby performing transmission and reception of signals between one interface 2 ₁ Nomigako station S _1. Operation selection switch SW ₀
Is adapted to a second contact point r _02, which is connected to the controller 1 can recognize the on-off operation selection switch SW ₀ by the controller 1. In the specific circuit of FIG. 3, the gate 4 is formed by adding an OR circuit to an AND circuit.
Controller 1 and interface 2 _1, 2 ₂ between the photocouplers 5a, but linked by 5b, the other configurations are the same as the basic configuration of FIG. 2. The white arrows indicate the connection to the positive electrode of the power supply, and the black arrows indicate the connection to the negative electrode of the power supply. Next, an operation at the time of starting the master station M will be described. When the master station M is started, as shown in FIG.
Read the status of S ₁ and S ₂ . Here, the operation selecting switch SW ₀ is off of interface 2 ₁ receiver 2b
If only the gate 4 is connected,
SEL terminal is "H", the resistance connection switch SW ₁ is off, TM1 terminal of the controller 1 becomes "H". In this state, only the slave stations can be connected to the terminal T _1, and because it is state of the slave station that terminates can connect two stations, the controller 1
If the number of terminal stations of the slave station is set to 2, the regular transmission processing is performed, and otherwise, processing such as displaying that the setting is incorrect is performed. SEL of controller 1
If the terminal is “H” and the TM1 terminal is “L”, _one terminal station can be connected to the terminal T ₁ , so that the number of terminal stations is set to one in the controller 1. If so, a steady transmission process is performed, and in other settings, an erroneous setting process is performed. On the other hand, when the SEL terminal of the controller 1 is "L", since both interface 2 _1, 2 ₂ are both operable either terminating resistors R _1, R ₂ are connected in each interface 2 _1, 2 ₂ Depending on whether or not, the number of terminal stations can be set to 3 or 4. In the above embodiment, the interface 2 _1, 2 ₂ While two provided, further, in the case of providing a large number of interfaces 2 ₁ to 2 _n, as shown in FIG. 5, the gate 4 of the multi-input AND Circuit. Further, by providing the operation selection switch SW ₀ in response to an appropriate interface 2 ₁ to 2 _n, which can be switched to the number of interfaces 2 ₁ to 2 _n to be used. In addition, each interface 2 ₁ to 2 _n, respectively provided with resistance connection switch SW ₁ to SW _n, so that the termination resistor R ₁ to R _n can be connected individually. Terminal T ₁ through T _n is provided equal to the interface 2 ₁ to 2 _n. For example, the case of providing three interfaces 2 ₁ to 2 _n, as shown in FIG. 1, the terminal T ₁ through T ₃ corresponding to the interface 2 ₁ to 2 ₃
Slave stations via transmission lines l _{1 to} l ₃ individually connected to
S _{1 to} S ₃ can be connected. In the use form as shown in FIG. ₁ , the total length of the transmission lines l _{1 to} l ₃ can be shortened, as apparent from comparison with FIG. Also, if multiple slave stations are required at each stage,
The transmission wiring may be performed between the slave stations as in the conventional case.

【The invention's effect】

As described above, the present invention relates to a multi-drop data transmission device based on the RS485 standard in which a master station and a plurality of slave stations are connected via a transmission line, and a controller for transmitting / receiving a signal to / from each slave station. A plurality of interfaces comprising a driver / receiver and connected in parallel to the controller; an operation selection switch for turning on / off the operation of each interface; a plurality of terminals for connecting slave stations to each interface; A plurality of resistance connection switches for selecting a connection state and a disconnection state of the terminating resistor are provided in the master station. The resistance connection switch is provided with a second contact connected to the controller. It is possible for the controller to recognize the connection and non-connection of the Connected to Le, since the respectively provided terminals for each interface, by connecting the slave stations to the terminals, there is an advantage that a plurality of slave stations may each connected via a separate transmission line. In addition, a plurality of resistance connection switches are provided for selecting a state of connecting and disconnecting a terminating resistor to a terminal connecting a slave station to each interface, and an operation selection switch is provided so that operation of each interface can be turned on / off. So that each interface of the master station can be set to terminate,
Only the required number of interfaces can be operated. In addition, since the resistor connection switch is provided with the second contact and the controller can recognize the connection and non-connection of the termination resistor by the resistance connection switch, the controller determines whether or not the termination resistor is connected for each interface. There is an advantage that the presence or absence of an erroneous setting can be determined by combining the state of the second contact and the impedance of the transmission line. Further, since it is possible to connect a plurality of slave stations to one interface by sending wiring as in the conventional case, it is possible to use together with the wiring method described in the prior art, and to suit the construction site. There is an effect that an optimal wiring method can be adopted.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a use mode of an embodiment of the present invention, FIG. 2 is a circuit diagram showing a basic configuration of a master station used in the embodiment, and FIG. 3 is a specific circuit of the master station used in the embodiment. 4 is a circuit diagram, FIG. 4 is an explanatory view of the operation of the master station used in the embodiment, FIG. 5 is a circuit diagram showing the basic configuration of the master station used in another embodiment of the present invention, and FIGS. 6 and 7 are conventional examples. It is a schematic structure figure showing the use form which shows. 1 ... controller, 2 ₁ , 2 ₂ ... interface, l ₁ , l ₃
…… Transmission line, M …… Master station, R ₁ , R ₂ …… Terminal resistance, S _{1 to} S
₃ … Slave station, SW ₀ … Operation selection switch, SW ₁ , SW ₂ … Resistance connection switch, T ₁ , T ₂ … Terminal.

Claims (1)

(57) [Claims] In a multi-drop type data transmission device based on the RS485 standard in which a master station and a plurality of slave stations are connected via a transmission line, the master station sends and receives signals to and from each slave station. A plurality of interfaces comprising a controller and a driver / receiver connected in parallel to the controller; an operation selection switch for turning on and off the operation of each interface; a plurality of terminals for connecting slave stations to each interface; A plurality of resistance connection switches for selecting a connection state and a disconnection state of the terminating resistor are provided, and the resistance connection switch is provided with a second contact connected to the controller. A data transmission device capable of recognizing connection and non-connection of a device by a controller.