JPH06164586A - 1:n communication system - Google Patents

Abstract

PURPOSE:To obtain an inexpensive 1:N communication system which is simple in the configuration of a master machine and a slave machine, and is not restricted from the viewpoint of connection. CONSTITUTION:The master machine P and all the slave machines C1, C2, ...are provided respectively with only one standard interface port 1,2. Besides, a transmission data terminal 6 among signal terminals in these interface ports 1,2 is constituted so as to be capable of floating electrically. Further, a transmission request terminal 8 and a terminal ready terminal 11 are an open collector output, and further, an interval between the adjacent slave machines is connected by a communication cable 5 connecting mutually the same terminals in the above-mentioned interface ports 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 1: N communication system in which a plurality of slave units are connected to one master unit so that the master unit and the slave units can communicate with each other. .

[0002]

2. Description of the Related Art As an interface port (connector) for connecting a computer and its terminal device to exchange data, there is an RS-232 port defined by the EIA (Electronic Industries Association). By using this RS-232 port, it is possible to connect a plurality of slave units to one master unit and to communicate between the master unit and the slave units.

FIG. 8 shows a conventional 1: N communication system in which a plurality of slave units are connected to one master unit so that the master unit and the slave units can communicate with each other. In this figure, reference numeral 81 is a master unit and 82 is N slave units. Then, the base unit 81 is provided with N RS-232 ports 83,
The slave unit 82 is provided with one RS-232 port 84, and the RS-232 port 83 on the master unit 81 side and the slave unit 8 are provided.
Between the RS-232 port 84 on the second side, RS-232
They are connected by a communication cable 85 at a ratio of 1: 1.

[0004]

However, in the above-mentioned conventional 1: N communication system, the main unit 81 and the slave unit 8 are connected.
It is necessary to provide RS-232 ports 83 equal to the number N of two, and there is a drawback that the configuration of the base device 81 becomes complicated accordingly. When the parent device 81 is installed at a position away from the child devices 82, N long RS-
The 232 communication cable 85 must be used, which is disadvantageous in that it is uneconomical. In addition, when communication is performed using a public line or the like using a modem (modulation / demodulation device), it is necessary to install one modem for each of the parent device 81 and all the child devices 82, and there are 2N modems for the entire system. In addition, there is a drawback that the cost for system configuration increases.

As a means for solving such a drawback, there is a communication system disclosed in Japanese Patent Laid-Open No. 62-171250. As shown in FIG. 9, this communication method uses each slave unit 91.
Each of the two RS-232 ports 92 and 93 is provided in each of the RS-232 ports 93, the connection is crossed in the slave unit 91, and a signal input / output from one RS-232 port 92 is transmitted to another RS232 port 93. It is designed to input and output from pins. In addition, 94 is a master unit, 95 is an RS-232 port provided in the master unit 94, and 96 is each slave unit 9
1 is an interface circuit, and 97 is a communication cable.

However, in the communication system according to the above publication, each RS 91 has two RS-232 ports 9
2, 93 must be provided. And one RS-2
32 port 92 is for upstream side (for master side), RS- on the other side
The 232 port 93 is limited to the downstream side (slave unit side), and there is a constraint that the master unit 94 must be installed at the upstream most upstream end. Further, if the connection between the upstream port 92, the downstream port 93 and the communication cable 97 is incorrect, there is a disadvantage that the entire system does not operate.

The present invention has been made with the above matters in mind, and an object of the present invention is to provide an inexpensive 1: N configuration which is simple in the master unit and the slave unit and is not restricted in connection.
To provide a communication system.

[0008]

In order to achieve the above object, a 1: N communication system according to the present invention has a single standard interface port for each of a master unit and a slave unit, and the interface port Of the signal terminals, the transmission data terminal is configured to be able to be electrically floated, the transmission request terminal and the terminal ready terminal are open collector outputs, and the adjacent slave units are connected to each other at the interface port. They are connected by a communication cable in which the same terminals are connected.

[0009]

In the 1: N communication system configured as described above, it is sufficient to provide only one standard interface port for each of the master unit and the slave unit, which simplifies the configuration of the slave unit and reduces the cost. Further, the master device may be installed at any position in the communication system.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing a 1: N communication system according to the present invention. In this figure, P is a DTE type master unit and C ₁ and C ₂ are slave units. In FIG. 1, for convenience, only _two slave units C ₁ and C ₂ are shown, but it is assumed that there are N slave units having the same configuration, and in the following description, the most upstream slave unit will be described. C ₁ and the downstream handset C
Set to _N (not shown).

Reference numeral 1 is a standard interface port provided in the master device P, 2 is a standard interface port provided in the slave devices C ₁ , C ₂ , ... C _N , and these interface ports 1 and 2 are, for example, RS- It is 232 ports. The details of these interface ports 1 and 2 will be described later. 3 is a child device C ₁ , C ₂ , ... C _N
Interface circuit provided in the RS-2
32 interface circuit. Reference numeral 4 is a communication cable for connecting the interface port 1 of the parent device P and the interface port 2 of the most upstream child device C ₁ . Reference numeral 5 is a communication cable that connects the interface ports 2 of the adjacent child devices, from the most upstream child device C _{1 to} the most downstream child device C _N.

FIG. 2 shows the configuration of interface ports 1 and 2 provided in the master unit P and the slave unit C ₁ (representative of the slave units C ₁ , C ₂ , ... C _N ) and the interface ports in the slave unit C ₁ . It is a figure which shows an example of a structure from 2 to the interface circuit 3.

The interface port 1 of the parent device P and the interface port 2 of the child device C ₁ are each composed of, for example, 25 pins (terminals). The interface port 1 of the master device P is, from the top, an SD (transmission data) terminal 6, an RD (reception data) terminal 7, an RS (transmission request) terminal 8, a CD (carry detection) terminal 9, and a CS (transmission possible). A terminal 10, an ER (terminal ready) terminal 11, a DR (data set ready) terminal 12, an ST2 (transmission clock) terminal 13, an RT (reception clock) terminal 14, and an ST1 (transmission clock) terminal 15 are provided. The interface port 2 of the child device C ₁ is provided with an (RT) (reception clock) terminal 16 in addition to the configuration of the interface port 1 of the parent device P.

In the interface port 1 of the base unit P, the RS terminal 8 and the DR terminal 12 are connected to each other through the crossover line 1.
It is connected by 7 but this interface port 1
And the terminal of the interface port 2 of the cordless handset C ₁ are cross-connected.

That is, the SD terminal 6 on the side of the parent device P and the child device C
The RD terminal 7 on the _1st side is connected by a line 18 of the cable 4, and the SD terminal 6 on the slave C ₁ side and the RD terminal 7 on the master P side are connected by a line 19. And R on the master side P
The S terminal 8 and the CD terminal 9 on the slave C ₁ side are connected by a line 20, and the RS terminal 8 on the slave C ₁ side and the CD terminal 9 on the master P side are connected by a line 21. Further, the CS terminal 10 on the master P side and the ER terminal 11 on the slave C ₁ side are connected to the line 2
2, the CS terminal 10 on the slave C ₁ side and the ER terminal 11 on the master P side are connected by a line 23. Furthermore, the ST2 terminal 13 on the master P side and the (RT) on the slave C ₁ side
Terminal 16 is connected by line 24, and ST on the side of handset C ₁
The 1 terminal 15 and the RT terminal 14 on the master device P side are connected by a line 25. Furthermore, the line 21 is connected to the DR terminal 12 on the slave C ₁ side by a line 26.

Although not shown in FIG. 2, the connection between the terminals of the interface port 2 in the most upstream handset C ₁ and the next handset C ₂ is made to correspond to the same terminals (pins). It is connected by a communication cable 5. For example, the SD terminal 6 of the handset C _{1 and} the SD terminal 6 of the handset C ₂ are connected. The same applies to the other terminals. In this example, the communication cable 5 is composed of 11 signal lines.

Next, the internal structure of the child device C ₁ will be described. Reference numeral 27 denotes a transmitter provided on the SD line 28 between the SD terminal 6 of the interface port 2 and the interface circuit 3, and has an OE (output enable) terminal 29 as shown in FIG. , This OE
When the terminal 29 is made inactive, the transmitter output has a high impedance.

Reference numeral 30 denotes an RS line 31 between the RS terminal 8 of the interface port 2 and the interface circuit 3.
Is an open collector output and the output is on (+) when the input is high, as shown in FIG.
12V), the output is off when the input is low (high
Impedance). The RS terminal 8 is connected to -12V via the resistor 32.

Reference numeral 33 denotes an ER line 3 between the ER terminal 11 of the interface port 2 and the interface circuit 3.
4, the transmitter is an open collector output as shown in FIG. 5, the output is on (high impedance) when the input is high, and the output is off (-12 V) when the input is low. Is configured to be. The ER terminal 11 is connected to + 12V via the resistor 35.

Reference numeral 36 denotes an RD line 37, a CD between the RD terminal 7, the CD terminal 9, the CS terminal 10 and the DR terminal 12 of the interface port 2 and the interface circuit 3.
A receiver provided on each of the line 38, the CS line 39, and the DR line 40, which is composed of, for example, a voltage converter, and converts the RS-232 signal level voltage into a logic level voltage.

The line 4 connected to the ST2 terminal 13
1 and a line 42 connected to the ST1 terminal 15 are connected to a receiver 4 having the same structure as the receiver 36 via a changeover switch 43.
4 and further the receiver 44 is connected to the interface circuit 3. Also, the (RT) terminal 16
Line 45 connecting to ST1 terminal 15 and line 4 connecting to ST1 terminal 15
6 is connected via a changeover switch 47 to a receiver 48 having the same structure as the receiver 36.
8 is connected to the interface circuit 3. Reference numeral 49 is an oscillator circuit, and its output is interlocked with switches (50) and (51) through (RT) terminal 16 and S respectively.
It is provided to the T1 terminal 15.

[0023] Then, a detailed description is omitted, the 1: In-N communication system, although the master unit P can start its own transmission, handset C _1, C _2, ... C _N are themselves transmitted Is configured to never start. That is, the slaves C ₁ , C ₂ , ... C _N can communicate only with the permission of the master P. Further, a unique ID code is set to each of the slave units C ₁ , C ₂ , ... C _N. And
The ID code is always attached to the data transmitted from the master P to the slaves C ₁ , C ₂ , ... C _N.

The operation of the 1: N communication system configured as described above will be described with reference to FIG.

First, when the parent device P starts transmission, the process is as follows. The parent device P turns on the RS terminal 8 in the interface port 2. This RS signal is input to the CD terminals 9 of the slave units C ₁ , C ₂ , ... C _N via the communication cables 4 and 5. As a result, the slave units C ₁ , C ₂ , ... C _N
Turns on the ER terminal 11. Child devices C ₁ , C ₂ , ... C
_The transmitter 33 provided at _N has an open collector output,
Moreover, since the ER terminal 11 is connected through a resistor 35 to + 12V, all handsets _{C 1, C 2, ... C} N is E
When the R terminal 11 is turned on, the ER signal for the master device P is turned on.

The ER signal enters the CS terminal 10 of the parent device P via the communication cables 4 and 5. As a result, the parent device P
Outputs data from the SD terminal 6. The data transmitted by the parent device P is transmitted via the communication cables 4 and 5 to the child device C ₁ ,
It is transmitted to C ₂ , ... C _N. The data transmitted by the parent device P is received by all the child devices C ₁ , C ₂ , ..., C _{N, and} a code collating circuit (not shown) inspects whether or not the data is addressed to itself. The slave units C ₁ , C ₂ , ..., C _{N take} in the data only when the data is addressed to itself, and respond to the base unit P in some cases.

The response is N slaves C ₁ , C ₂ , ... C.
The only child device of _N that is allowed to respond with information from the parent device P (hereinafter referred to as C _X (not shown))
Only do. This child device C _X turns on the RS terminal 8.
Since the transmitter 30 provided in each of the slaves C ₁ , C ₂ , ..., C _N has an open collector output, and the RS terminal 8 is connected to −12V via the resistor 32, the slave C _X is RS.
When the terminal 8 is turned on, the RS signal for the master device P is turned on. The RS signal enters the CD terminal 9 of the parent device P via the communication cables 4 and 5, and at the same time, the child devices C ₁ , C ₂ , ... C.
It enters the _N DR terminal 12 and is transmitted to all the slave units C ₁ , C ₂ , ... C _N via the communication cable 5.

Upon receiving the RS signal, the base unit P turns on the ER terminal 11. This output enters the CS terminals 10 of the slave units C ₁ , C ₂ , ... C _N via the communication cables 4 and 5. As a result, the child device C _X enables the OE terminal 29 (see FIG. 3) of the transmitter 27 and transmits data from the SD terminal 6. The data transmitted by the child device C _X enters the RD terminal 7 of the parent device P via the communication cables 4 and 5 and is received by the parent device P.

By the way, the master P and the slaves C ₁ , C ₂ , ... C
_When performing synchronous communication when _N and _N are directly connected to each other, the synchronous clock is output from the most downstream child device C _N.
For that purpose, only the downstreammost slave unit C _N has the switches 50, 51.
Turn on. Synchronous clock, the slave unit C _1, C ₂ via the communication cable 5, to enter the ... RT terminal 14, ST1 terminal 15 of C _N, each child device C _1, C _2, the ... C _N, a synchronous clock In order to obtain it, the switches 43 and 47 are switched as shown in FIG. In this case, the switches 43, 47,
The switching of 50 and 51 may be performed manually, or whether each slave unit C ₁ , C ₂ , ... C _N is at the end of the reception clock or transmission clock based on the voltage level of each signal line. to determine and whether is in which line, handset _{C 1, C 2, ... C} N
You may make it switch itself.

The present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. For example, a modem may be provided at any position between the master P and the slaves C ₁ , C ₂ , ... C _N. In this case, the slave unit and the modem may be connected to the same terminal (pin). When a modem is provided between the master P and the slave C ₁ , the master P and the modem may be connected to the same terminal (pin).
Even when a modem is used, the slave units C ₁ , C
The operation of ₂ , ..., C _N is the same as that of the parent device P. However, when the transmission clock and the reception clock are output from the RT and ST2 of the modem in the case of performing synchronous communication, the switch 5 is used in all the slave units downstream of the modem.
0 and 51 are turned off, and the switches 43 and 47 are switched to the contacts on the opposite side to that shown in FIG.

Further, in the above embodiment, when the master device P is the DTE type, the RS terminal 8 of the master device P and the CD of the slave device C ₁ are used.
Terminal 9, the ER terminal 1 station CS terminal 10 and the slave device C ₁ of P
Although a cross cable for connecting 1 and 1 is used, the RS terminal 8 of the parent device P and the CS terminal 10 of the child device C ₁ , the ER terminal 11 of the parent device P and the DR terminal 12 of the child device C ₁ are respectively You may make it use the cross cable connected.

In the case of asynchronous communication, (RT) terminal 16, ST2 terminal 13, RT terminal 14, ST1 terminal 15
No wiring or circuit is required.

Further, the transmitter 27 shown in FIGS.
In the circuit configurations of 30 and 33, the photocoupler 52 is used for isolation, but if it is not necessary, a transistor may be used instead of the photocoupler 52.

Furthermore, the parent machine P and the child machines C ₁ , C ₂ , ...
At the time of connection with C _N , a connector 53 having connection ports 53a, 53b, 53c on three sides as shown in FIG. 6 may be used and configured as shown in FIG.

Further, in the above embodiment, the interface ports 1 and 2 conforming to RS-232 were used. As a matter of course, the one compliant with other standards such as 35 may be used.

[0036]

The present invention constructed as described above has the following effects. Only one interface port needs to be provided on the base unit. Only one interface port may be provided on the child device. Even if the parent device and the child device group are separated, the adjacent child devices can be connected to each other with a short communication cable. The parent device may be installed at any position in the system. Even if the master unit and the slave units are separated, communication can be performed by providing a modem in the middle and using a public line or the like. In that case, one pair (two) of modems is sufficient. Therefore, it is possible to obtain an inexpensive 1: N communication system in which the configuration of the master unit and the slave unit is simple and there is no restriction in connection.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a 1: N communication system according to the present invention.

FIG. 2 is a diagram schematically showing an example of a configuration of a master unit and a slave unit.

FIG. 3 is a diagram showing a circuit configuration of a transmitter used in the slave unit.

FIG. 4 is a diagram showing a circuit configuration of another transmitter used in the slave unit.

FIG. 5 is a diagram showing a circuit configuration of still another transmitter used in the slave unit.

FIG. 6 is a diagram showing an example of a connector used for connecting a master unit, a slave unit, and slave units.

FIG. 7 is a diagram showing a configuration example of a system using the connector.

FIG. 8 is a diagram for explaining a conventional example.

FIG. 9 is a diagram for explaining another conventional example.

[Explanation of symbols]

P ... Parent machine, C ₁ , C ₂ ... Child machine, 1, 2 ... Interface port, 5 ... Communication cable, 6 ... Transmission data terminal, 8
... Send request terminal, 11 ... Terminal ready terminal.

Claims (1)

[Claims] 1. A 1: N communication system configured to connect a plurality of slave units to one master unit so that the master unit and the slave units can communicate with each other. All of the machines are equipped with only one standard interface port, and among the signal terminals of this interface port, the transmission data terminal can be electrically floated, and the transmission request terminal and terminal ready terminal are also provided. Is an open collector output, and the adjacent slave units are connected to each other by a communication cable in which the same terminals in the interface port are connected to each other.