JP3845302B2 - Multi-connection interface circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an interface circuit, and more particularly to a multi-connection interface circuit in which data communication is performed by connecting a plurality of devices one-to-one with an RS422 interface or one-to-one with an RS485 interface.
[0002]
[Prior art]
With the spread of computers, devices such as a large number of computers are interconnected via a communication line to form a network, and a communication network for data communication with each other is configured. Prior arts in or related to such a technical field are, for example, “data terminal device” (first prior art) in Japanese Patent Laid-Open No. 1-289851 and “data line termination device” (second in Japanese Patent Laid-Open No. 1-300756). And the "data transmission device" (third prior art) of JP-A-11-27184.
[0003]
The first prior art described above includes a processing circuit as a DTE (Data Terminal Equipment), a serial communication interface circuit connected to the DTE processing circuit for transmitting and receiving signals, an output terminal for transmitting signals, and a signal. It consists of an input terminal for receiving and a two-pole double-throw switch that is connected to the input / output terminal and switches the route of the input / output signal from the outside. Disclosure of technology that enables switching between DTE-DCE connection and DTE-DTE connection by cross-connecting or straight-connecting cable by switching signal input / output route by switching two-pole double-throw switch is doing.
[0004]
In the second prior art, the route of the input / output signal of the signal line is switched by incorporating a switch for switching the signal line and the control line in the DTE device. By switching the switch built in the DTE, the input / output route of the signal is switched, and the cable for the DTE-DCE connection and the DTE-DTE connection can be connected to either the cross connection or the straight connection. The technology is disclosed.
[0005]
Further, the third prior art includes a transmission device that includes a transmission line circuit and a transceiver circuit and transmits / receives a data signal to / from the first transmission line via the first connector, and a second data signal that is connected to or disconnected from the first connector. A second connector that bypasses the transmission line and transmits / receives, a termination resistor that is provided in the transmission device and inserts a resistance into the first and second transmission lines to form a termination mode; and a resistance that is provided to the first and second transmission lines Terminating resistor changeover switch for switching between inserting and configuring the terminal mode or short-circuiting the first and second transmission lines to configure the through mode, and terminal switching control connected to the host CPU for controlling the terminal resistance switching In the normal state, the terminal resistance changeover switch of the terminal station of the network is set to the terminal mode, and the other intermediate stations are set to the through mode. A technique for detecting a disconnection or a short-circuit failure of a transmission cable by switching terminal stations one after another when a transmission abnormality occurs is disclosed.
[0006]
FIG. 3 is a system configuration diagram of a conventional multi-connection communication network. This communication network includes a plurality of master stations and one or more slave stations connected to these master stations. In the specific example shown in FIG. 3, the slave station 11 </ b> A is connected to the master station 1, and the slave stations 21 </ b> A and 22 </ b> A are connected to the master station 2. Further, the slave station 11A performs communication between the slave station 11N, the slave station 21A communicates with the slave station 21N, and the slave station 22A communicates with the slave station 22N. Here, the master stations 1 and 2 are connected by a cross cable 31. The master station 1 and the slave station 11A and the master station 2 and the slave stations 21A and 22A are connected by a multi-connection cross cable 32 which is an RS485 (V.11) interface. In FIG. 3, numerals 1 and 2 on the right or left end of the master station and the slave station respectively indicate connector numbers.
[0007]
Next, FIG. 4 shows a circuit configuration diagram of a conventional multi-connection interface. 4A shows a parent station-parent station interface circuit, and FIG. 4B shows a master-slave multi-connection interface circuit. 4A includes a PORT-A SYNC 40, drivers 41 and 44, receivers 42 and 45, termination resistors 43 and 46, and a connector 47. The driver 41 and the receiver 42 are driven by a clock transmission signal, and the driver 44 is driven by a transmission control signal. The complementary output of the driver 41 is connected to the 4th and 5th pins of the first connector 47. The output of the driver 44 is connected to the 1 and 2 pins of the connector 47. Further, pins 3 and 6 of the connector 47 are input to the receiver 45.
[0008]
A synchronous communication circuit (PORT-A SYNC) 40 performs synchronous communication between the master station and the master station. The driver 41 outputs a clock when outputting communication data. The receiver 42 inputs a clock when inputting communication data. The driver 44 outputs communication data. The receiver 45 inputs communication data. The connector 47 is used for communication connection between master stations.
[0009]
On the other hand, communication between the master station and the slave station shown in FIG. 4B includes an asynchronous communication circuit (PORT-B ASYNC) 50, a Hi-Z (high impedance) control 52, a driver 51, a receiver 53, and a termination resistor 54. And the second connector 55. The Hi-Z control 52 that controls the driver 51 is controlled by a Hi-Z control INH signal. The output of the driver 51 is connected to the 1 and 2 pins of the connector 55, and the 3 and 6 pins are connected to the input of the receiver 53. PORT-B ASYNC performs asynchronous communication between a master station and a slave station. The driver 51 outputs communication data. The receiver 53 inputs communication data. The Hi-Z control 52 controls the output of communication data. Note that the termination resistor 54 is mounted only at the final stage of multi-connection. The connector 55 is used for communication between the master station and the slave station.
[0010]
Since the same circuit is used in the connected device, the cross cable 31 is used for the connection between the master station and the master station. For the connection between the master station and the slave station, a cross cable 32 capable of multi-connection is used.
[0011]
[Problems to be solved by the invention]
The prior art described above has several problems as follows. First, since the first and second prior arts are basically based on one-to-one communication, a cable capable of multi-connection is required when applied to RS485 communication of one-to-multiple communication. Therefore, when expanding, it is necessary to replace the cable, and it is necessary to prepare in advance connectors having the maximum number of expansions. The reason for this is to switch the signal route of transmission / reception data and control signal using a changeover switch (double pole double throw switch), etc., fix the input / output pins between the one-to-one opposing devices, and cross / straight of the cable This is because the connection by multi-connection is not considered because the connection is possible regardless of the connection.
[0012]
Further, in the third conventional technology, a straight cable is required for connection between devices, a straight cable is required for connection between DTE and DCE, and a cross cable is required between DTE and DTE. / Cross cable needs to be prepared. The reason for this is that the communication data input / output pin arrangement is staggered in the DTE-DCE connection, so it can be connected with a one-to-one cable, but the communication data input / output pin arrangement is the same in the DTE-DTE connection. This is because when a connection is made with a one-to-one straight cable, a signal collision occurs and a cross cable is required.
[0013]
Furthermore, when adding a slave station, a termination resistor mounted only when the final stage of multi-connection is required to be attached only to the final stage device in order to make the best use of the termination effect. Therefore, it becomes necessary to remove or attach the termination resistor, or a dedicated panel depending on whether or not the termination resistor is attached is required.
[0014]
OBJECT OF THE INVENTION
The present invention has been made in view of the above-described problems of the prior art, and only one type of cable (straight) is required for connection between devices. When a device is added, only a cable needs to be added. It is an object of the present invention to provide a multi-connection interface circuit with high maintainability and capable of multi-connection that does not require a terminal resistor and does not require removal / attachment of a termination resistor.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems, the multi-connection interface circuit according to the present invention employs the following characteristic configuration.
[0016]
(1) A circuit for synchronous communication, a circuit for asynchronous communication, a first connector and a second connector, and a clock input / output circuit and communication data input / output between the synchronous communication circuit and the first connector In a multi-connection interface circuit in which a circuit is connected, and a communication data input / output circuit is connected between the asynchronous communication circuit and the second connector,
Between the communication data input / output circuit between the synchronous communication circuit and the first connector, and the communication data input / output circuit between the asynchronous communication circuit and the second connector, A multi-connection interface circuit provided with a route switch.
[0017]
(2) The multi-connection interface circuit according to (1), wherein a driver / receiver pair is used for each communication data input / output circuit.
[0018]
(3) The changeover switch includes the communication data input circuit side of the synchronous communication circuit and the asynchronous communication circuit, and the first connector side of the communication data input / output circuit of the synchronous communication circuit, respectively. And the change-over switch provided on the first connector side selects communication data of the synchronous communication circuit or the asynchronous communication circuit. Connection interface circuit.
[0019]
(4) A termination resistor is selectively connected to the driver / receiver of the communication data input / output circuit between the asynchronous communication circuit and the second connector via a changeover switch. The multi-connection interface circuit according to (2) or (3).
[0020]
(5) The multi-connection interface circuit according to any one of (1) to (4), wherein the changeover switch and the driver / receiver pair are controlled by a communication instruction from a host CPU or the like.
[0021]
(6) The multi-connection interface circuit according to any one of (1) to (5), wherein the connection is made with a straight cable regardless of connection between the master stations, between the master station and the slave stations, or between the slave stations.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration and operation of a preferred embodiment of a multi-connection interface circuit according to the present invention will be described in detail with reference to the accompanying drawings.
[0023]
FIG. 1 is a system configuration diagram of a communication network using a multi-connection interface circuit according to the present invention. A multi-connection communication network 200 shown in FIG. 1 includes a plurality of master stations and a plurality of slave stations that are multi-connected to these master stations. In the specific example shown in FIG. 1, there are a plurality of (N) parent stations including a first parent station 201, a second parent station 202,..., An N−1 parent station 209, and an Nth parent station 210. A slave station 203 is connected to the first master station 201, and one or more slave stations can be multi-connected as indicated by a broken line. On the other hand, the second master station 202 is multi-connected with a slave station 205 and a slave station 206. The slave station 205 is multi-drop (intermediate), and the slave station 206 is multi-drop (end point).
[0024]
In FIG. 1, the master station 201 communicates with the master station 209, and the master station 202 communicates with the master station 210. The slave stations 203, 205, and 206 are in communication with the slave stations 204, 207, and 208, respectively. Here, a one-to-one straight cable is used between the master station 201 and the master station 202, between the master station 201 and the slave station 203, between the master station 202 and the slave station 205, and between the slave station 205 and the slave station 206. That is, in the system configuration of the communication network of the present invention shown in FIG. 1, the RS422 interface connection between the master station 201 and the master station 202 and the RS485 interface connection between the master station 201 and the slave station 203 are between the connectors. All are connected by a one-to-one straight cable. The numbers 1 and 2 at the left or right end of the master stations 201 and 202 and the slave stations 203 to 208 indicate a first connector and a second connector described later.
[0025]
Next, FIG. 2 is a circuit configuration diagram of a preferred embodiment of a multi-connection interface circuit according to the present invention used for inter-device connection in a communication network as shown in FIG. The multi-connection interface circuit 100 operates in accordance with a communication instruction from a host CPU (central processing unit) 102. The multi-connection interface circuit 100 includes a synchronous communication circuit (PORT-A SYNC) 115, an asynchronous communication circuit (PORT-B SYNC) 125, a driver / receiver pair 103/104, 107/108, 110/111, 118/119, 120/121, inverters (inverting circuits) 105, 113, 122, AND (logical product) circuit 123, termination resistors 106, 109, 112, 127, 128, changeover switches 114, 116, 117, 124, 126 129 and 8-pin first connector 130 and second connector 131.
[0026]
Pins 1 and 2 of the connector 130 are connected to the driver 107 / receiver 108 or the driver 118 / receiver 119 via the changeover switch 116. The 4th and 5th pins are connected to the driver 103 and the receiver 104, respectively. Pins 3 and 6 are connected to the driver 110 / receiver 111 or the driver 120 / receiver 121 via the changeover switch 117. Termination resistors 106, 109 and 112 are connected to driver 103 / receiver 104, driver 107 / receiver 108 and driver 110 / receiver 111, respectively. Termination resistor 127 is selectively connected to driver 118 and receiver 119 by changeover switch 126. On the other hand, the termination resistor 128 is selectively connected to the driver 120 and the receiver 121 by the changeover switch 129.
[0027]
In the multi-connection interface circuit 100 of FIG. 2, the driver / receiver pairs 107/108, 110/111, 118/119, 120/121 and the changeover switches 114, 116, 117, 124, 126, 129 are communicated from the host CPU 102. Controlled by an instruction (control signal).
[0028]
Next, the operation of the multi-connection interface circuit 100 shown in FIG. 2 will be described. The communication circuit 115 that performs communication using the RS422 interface that performs one-to-one communication according to a communication instruction from the host CPU 102 outputs communication data when performing communication using the synchronous (SYNC) communication method with respect to the RS422 interface. At this time, a clock is output from the driver 103 to the 4th pin of the connector 130. On the other hand, when inputting communication data, a clock is input from the receiver 104. The termination resistor 106 terminates a signal when a clock is input. The communication circuit 115 controls the inverter 105 to output a clock from the driver 103 when outputting data. When the communication circuit 115 is instructed by the host CPU 102 to perform asynchronous communication, the driver 103 and the receiver 104 are not used.
[0029]
A driver 107 that outputs communication data from the communication circuit 115, a receiver 108 that inputs communication data from the opposite device, a termination resistor 109 that terminates the signal at the time of input, and communication data that is output from the communication circuit 115 A driver 110 for receiving communication data, a receiver 111 for inputting communication data from an opposing device, and a termination resistor 112 for terminating a signal when input, an inverter 113 for selecting an input / output route of communication data, and data received by the receiver 108 / receiver 111 A switch 114 that performs route switching presets which route is input or output of communication data in accordance with an instruction from the host CPU 102.
[0030]
On the other hand, the communication circuit (PORT-B ASYNC) 125 that performs asynchronous (ASYNC) communication using the RS485 interface that performs one-to-multiple communication in accordance with a communication instruction from the host CPU 102 is used by the driver 118 when used in the master station. Output communication data from. On the other hand, when used in a slave station, communication data is input from the receiver 119. When used in a slave station, communication data is output from the driver 120. When used in the master station, communication data from each slave station is input from the receiver 121. In accordance with an instruction from the host CPU 102, the master station or slave station use mode is controlled by the inverter 122 and the changeover switch 124 for input / output route selection. When the slave station is used from the communication circuit 125, control is performed by an AND circuit 123 that performs signal output control only when communication data is output.
[0031]
When the master station mode is used, communication data is input / output between the master stations via the RS422 interface. On the other hand, when using the slave station mode, asynchronous communication data is input between the master stations in the case of the first slave station directly under the master station and between the slave stations in the second slave station or later by the RS485 interface. A connector 130 for performing output, a connector 131 for performing asynchronous communication data input / output between the slave stations when using the master station mode by the RS485 interface, and an asynchronous communication data input / output between the slave stations when using the slave station mode; The signals input / output from the connector 130 when the slave station is used are switched by the selector switches 116 and 117 for switching the route of the signal to the connector 131 side.
Termination resistors 127 and 128 that terminate when the slave station is in the final stage of multi-connection are a selector switch 126 that switches a route to the termination resistor 127 and a selector switch 129 that switches a route to the termination resistor 128. Switch with.
[0032]
The configuration and operation of the preferred embodiment of the multi-connection interface circuit according to the present invention have been described in detail above. However, such an embodiment is merely an example of the present invention and does not limit the present invention. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.
[0033]
【The invention's effect】
As understood from the above description, according to the multi-connection interface circuit of the present invention, the following remarkable effects in practical use can be obtained. First, all devices can be connected by straight cables regardless of the type of the RS422 interface / RS485 interface or the type of DCE (data circuit terminating device) / DTE (data terminal device). Therefore, it is not necessary to prepare a plurality of types of cables, and expansion is easy.
[0034]
Secondly, when one or more slave stations are added by multi-connection, cable replacement is not necessary, and it can be handled only by adding a one-to-one straight cable.
[0035]
Third, the termination resistor required at the farthest point (end point) of the multi-connection can be automatically removed / attached by operating the changeover switch based on an instruction from the host CPU.
[Brief description of the drawings]
FIG. 1 is a system configuration example of a communication network to which a multi-connection interface circuit of the present invention can be applied.
FIG. 2 is a circuit diagram of a preferred embodiment of a multi-connection interface circuit according to the present invention.
FIG. 3 is a system configuration example of a conventional communication network.
FIG. 4 is a circuit configuration diagram of a conventional multi-connection interface circuit.
[Explanation of symbols]
100 Multi-connection interface circuit 102 Host CPU
103, 107, 110, 118, 120 Driver 104, 108, 111, 119, 121 Receiver 105, 113, 122 Inverter 106, 109, 112, 127, 128 Termination resistor 115, 125 Communication circuit 114, 116, 117, 124 126, 129 Switch 130, 131 Connector

Claims (6)

The circuit includes a synchronous communication circuit, an asynchronous communication circuit, a first connector and a second connector, and a clock input / output circuit and a communication data input / output circuit are connected between the synchronous communication circuit and the first connector. A multi-connection interface circuit in which a communication data input / output circuit is connected between the asynchronous communication circuit and the second connector;
Between the communication data input / output circuit between the synchronous communication circuit and the first connector, and the communication data input / output circuit between the asynchronous communication circuit and the second connector, A multi-connection interface circuit comprising a route changeover switch. 2. The multi-connection interface circuit according to claim 1, wherein a driver / receiver pair is used for each communication data input / output circuit. The changeover switch is provided on the communication data input circuit side of the synchronous communication circuit and the asynchronous communication circuit, and on the first connector side of the communication data input / output circuit of the synchronous communication circuit, respectively. The multi-connection according to claim 1, wherein the changeover switch provided on the first connector side selects communication data of the synchronous communication circuit or the asynchronous communication circuit. Interface circuit. The terminal resistor is selectively connected to the driver / receiver of the communication data input / output circuit between the asynchronous communication circuit and the second connector via a changeover switch. 4. The multi-connection interface circuit according to 1, 2, or 3. 5. The multi-connection interface circuit according to claim 1, wherein the selector switch and the driver / receiver pair are controlled by a communication instruction from a host CPU or the like. 6. The multi-connection interface circuit according to claim 1, wherein all of the connections are made with a straight cable regardless of connection between the master stations, between the master station and the slave stations, or between the slave stations.

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