JPS60230745A - Data transmission equipment in loop type communication system - Google Patents

Abstract

PURPOSE:To constitute a loop network at a low cost by selecting and sending out a receiving signal from a circuit in other time than the time when a prescribed time has elapsed, after completing to send out a send-out signal to the circuit by a multiplexer. CONSTITUTION:A signal SR received 17 from a circuit L is inputted to a multiplexer MX18 and an AND circuit 19. AT the first stage, a Q output of an FF28 is in an L level, and the MX18 selects the signal SR and sends it out to the circuit L through a transmitting circuit 20. At the same time, the circuit 19 is opened, and the signal SR is S/P-converted 21 and inputted to a controlling circuit 22. When a signal addressed to its own station is detected in input signals, the circuit 22 sends its signal to an electronic device 13. A signal sent to other station from the device 13 is P/S-converted 23 and supplied as a signal ST to the MX18. At the same time, an H level signal is outputted from a T terminal of the circuit 23, the FF28 is set, and a counter 25 is reset. The Q output of the FF28 becomes an H level, and the MX18 selects and outputs the signal ST. When a counting value of the counter 25 which has counted a clock phi has allowed to coincide with a constant K constant, the MX18 selects the signal SR.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission device used in a loop communication system in which a plurality of devices are connected in a loop and data is transmitted between the devices.

[Prior art]

In recent years, various LANs (Local Area Networks) have been developed that interconnect a plurality of electronic devices installed within a relatively narrow area, for example, one factory, and transmit data between the devices. This LAAN includes a bus network that connects a plurality of slave stations 3, 3, . . . to a path line 2 connected to a master station 1, as shown in FIG. There is a loop network that connects 4.4... in a loop, but the former has disadvantages compared to the latter, such as not being able to use optical fibers and having higher line costs. Therefore, especially for simple LAN
In this case, a loop network is preferable.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its object is to provide a data transmission device that has a simple configuration and can be configured as a loop network.

[Structure of the invention]

This invention comprises a multiplexer, in which nine received signals received from a line are supplied to a seventh input terminal, and a transmission signal to be transmitted to the line is supplied to a second input terminal, and a signal obtained at the output terminal of this multiplexer is supplied to the line. It has a transmitting means for sending data, and a control means for switching and controlling the multiplexer. The control means electrically connects the second input terminal and the output terminal of the multiplexer for a period of time during which the transmission signal is output to the multiplexer and for a certain period of time after the output of the transmission signal to the multiplexer is completed. and at other times, the seventh input terminal and the output terminal of the multiplexer are electrically connected.

〔Example〕

FIG. 1 shows a data transmission device 11 according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of a loop communication system 12 configured using the same data transmission devices 11, 11, etc. In these figures, reference numeral 13 indicates a factory, for example. These are electronic devices installed in various places inside the building. It should be noted that the communication system shown in FIG. 2 is a system that operates according to the polling/select note system.

To explain in detail below, in FIG. 7, reference numeral 17 is a receiving circuit, which synchronously receives a signal supplied from a transmission line (cable) L, and outputs a received signal SR to a multiplexer 18 and an AND gate 19.

The multiplexer 18 connects its control terminal C to
When the 1'' signal is applied, the input terminal B and the output terminal are electrically connected, and when the 60'' signal is applied to the control terminal C, the input terminal A and the output terminal are electrically connected.

The transmitting circuit 20 amplifies the output signal of the multiplexer 18 and outputs it to the transmission line.

Reference numeral 21 denotes an S/P (serial/parallel) conversion circuit that converts serial data supplied to its input terminal into parallel data, and its output is supplied to a control circuit 22 . 2
Reference numeral 3 denotes a P/S (parallel/serial) conversion circuit that converts parallel data outputted from the control circuit 22 into serial data, and its output is supplied to the input terminal B of the multiplexer 18 as a transmission signal ST. This P/S conversion circuit 23 outputs the 61# signal from the terminal T while outputting the transmission signal ST. 24 is a constant setting circuit for setting a line-sequential time constant (hereinafter referred to as K constant). Here, the K constant is a constant whose value corresponds to a time slightly longer than the time the signal takes to go around the loop shown in FIG. In other words, it is a constant whose value corresponds to a time that is slightly larger than the total time of the signal delay time due to the transmission line, L...K, and the signal delay time in the data transmission equipment -tt, xx... Determined by system configuration. Incidentally, the constant setting circuit 24 is constituted by, for example, a digital switch. The counter 25 counts constant periodic four-clock pulses φ output from the oscillator 26, and is reset by the "1" signal output from the P/S conversion circuit 23. The comparator 27 compares the count output of the counter 25 and the output of the K constant setting circuit z4, and outputs a match signal EQ ('1'' signal) when the two match. 28 is a flip-flop (hereinafter referred to as FF). The Q output signal is supplied to the control terminal C of the multiplexer 18 and also supplied to the AND gate 19 via the inverter 29.

Next, the operation of the above-mentioned data transmission device 11 will be explained. First, in the initial state, the FF 28 is reset, so the input terminal A and the output terminal of the multiplexer 18 are electrically connected, and the AND gate 19 is in an open state. In this state, the received signal SR output from the receiving circuit 17 is supplied to the transmitting circuit 20 via the multiplexer 18, and is output from the transmitting circuit 20 to the transmission line, and is also sent via the antenna 19 to the S/ P
The signal is supplied to a conversion circuit 21 , where it is converted into parallel data and supplied to a control circuit 22 . The control circuit 22ti constantly checks the data output from the S/P conversion circuit 21. When a code indicating data transmission to the local station is detected, the data outputted from the S/P conversion circuit is sequentially captured and the captured data is supplied to the electronic device 13. Furthermore, when there is data to be sent to another station, the control circuit 22 detects a code that instructs the own station to transmit data, and then sequentially sends the data to be transmitted to the P/S conversion circuit 23. Output. P/13
The conversion circuit 23 converts the supplied data into serial data, outputs it as a transmission signal ST, and outputs it from one terminal T.
'1m signal is output. This “1” signal is F F 2
The signal is supplied to the set terminal S of '8 and the reset terminal R of the counter 25, which sets the FF 28 and resets the counter 25. When the FF 28 is set and its Q output signal becomes a 61'' signal, the AND gate 19 is closed and the input terminal B and output terminal of the multiplexer 18 are electrically connected.

As a result, the transmission signal ST is sequentially outputted to the transmission 1sL via the multiplexer 18 and the transmission circuit 20. When the output of the transmission signal ST from the P/S conversion circuit 23 is completed, a '0'' signal is output from the terminal T of the P/S conversion circuit 23.Then, the counter 25 counts the clock pulse φ by the amplifier. Then, when the count output of the counter 25 matches the output of the constant setting circuit 24',
A match signal EQ is output from the comparator n and supplied to the reset terminal R of the FF 28. After this, the FF 28 is reset and its Q output signal returns to the ON signal, so the AND gate 19 is opened again and the input terminal A and the output terminal of the multiplexer 18 are electrically connected. .

In this way, in the circuit shown in FIG. 1, even after the P/S conversion circuit 23 finishes outputting the transmission signal ST, the FF 28 is kept in the set state for a certain period of time determined by the output data of the constant setting circuit 24. Received signal SR from K
is prohibited from flowing to the transmitting circuit 20. The reason for this is as follows. In other words, there is a certain delay time (line-sequential time) in the loop shown in FIG. The signal is transmitted, Ii! There will be interference at L. Therefore, in the circuit shown in FIG. 2, the time set by the constant setting circuit 24 has elapsed after the last transmitted signal has gone around the loop, that is, from the time when the output of the transmission signal ST has ended. At that point, the multiplexer 18 is switched.

FIG. 3 is a timing diagram of the above-mentioned data transmission and reception,
In this figure, the mark indicates the transmission signal S from the P/S conversion circuit.
The timing at which T is output (b) is at the timing of the Q output signal of the FF 28. In this (b), time T
This is the running time set by the constant setting circuit 24.

(c) is the 4 timing when the received signal SR is output from the receiving circuit 1725), and in this (c), Dl is the timing of data sent from another station to the own station, D2ti (a)
This is the timing at which the nine signals transmitted from the own station are received at the timing shown in . ) is the S/P conversion circuit 21
This is the timing at which the received signal SR is supplied to the input terminal of.

Note that although the above-mentioned previous embodiment uses a metal cable as the transmission line, it is of course possible to use an optical fiber as the transmission line in the present invention.

〔Effect of the invention〕

As described above, according to the present invention, a loop type communication system can be realized with an extremely simple and inexpensive configuration, and is therefore particularly suitable for use in a simple communication system. Further, the data transmission device according to the present invention can use either metal cables or optical fibers, and has the advantage that line costs are lower than conventional bus networks. Further, the data transmission device according to the present invention has the advantage that data communication software (for example, polling select system software) in a conventional bus network can be used without any modification.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of a loop communication system to which the same embodiment is applied, FIG. 3 is a timing diagram for explaining the operation of the same embodiment, and FIGS. μ and 3 respectively show a bus network, FIG. 3 is a diagram showing the configuration of a loop network. 18. Song multiplexer, 2o... Song sending circuit, 24
...K constant setting circuit, 25... Song counter, 2
6... Oscillator, 27... Song comparator, 28...
···flip flop. Figure 2 Figure 3 C-nin Figure 4 Figure 5

Claims (1)

[Claims] a multiplexer, a receiving signal received from a line is supplied to a seventh input terminal; a transmitting signal to be sent to one line is supplied to a first input terminal; a control means for controlling the multiplexer; and a control means for controlling the multiplexer; and transmitting means for transmitting a signal to the line, and the control means:
The first input terminal and the output terminal of the multiplexer are electrically connected for a period of time during which the transmission signal is output to the multiplexer and for a certain period of time after the output of the transmission signal to the multiplexer is completed, and at other times. A data transmission device in a loop communication system, characterized in that a first input terminal and an output terminal of the multiplexer are electrically connected.