JP5395593B2 - RS-232C signal remote transmission system - Google Patents

Description

  The present invention relates to an RS-232C signal remote transmission system and a transmission relay device used therefor. In more detail, when communication failure occurs in one line segment and communication between both RS-232C devices becomes impossible, information on the signal status of the line segment on the remote side from the other line segment The present invention relates to an RS-232C signal remote transmission system and a transmission relay device.

  RS-232C signal, which is a single-ended signal, is only supported up to 15m in transmission distance, so RS-232C equipment that communicates with RS-232C signal (terminal specification equipment or modem) The specification device cannot communicate with a distance exceeding 15 m as it is.

  As a remote transmission system that transmits RS-232C signals between RS-232C devices at remote locations, use a relay device that mutually converts RS-232C signals and RS-422 signals, and set a long transmission distance. There is already known a system for relaying using an RS-422 signal which is a differential signal.

This system, for example, between two RS-232C devices at remote locations, a first relay device that converts RS-232C signals into RS-422 signals and RS-422 signals into RS-232C signals. A second relay device is arranged to transmit an RS-232C signal from one RS-232C device to the other RS-232C device at a remote location.
Note that a relay device (represented as “input / output interface” in Patent Document 1) that mutually converts an RS-232C signal and an RS-422 signal has already been disclosed in Patent Document 1.

JP-A-5-158590

However, the above-described remote transmission system using a device equivalent to the relay device described in Patent Document 1 has the following problems.
In the conventional system, the first and second relay devices only perform mutual conversion between the RS-232C signal and the RS-422 signal, so one RS-232C device (upper side device) and the other In RS-232C equipment (lower-order equipment), the line segment of the transmission path (the network through which data arrives) is divided.

  For this reason, for example, if some communication failure occurs in one line segment and communication between both RS-232C devices becomes impossible, the signal status of the line segment on the remote side from the other line segment The information of the communication failure is not known because the information cannot be acquired. In other words, since the signal state information cannot be shared between the two line segments, in some cases, this identification takes time, and recovery may be delayed.

  In order to provide a so-called monitoring function in which one of the two line segments is a management side and the management side can obtain signal state information of other line segments on the remote side, for example, a CPU (Central Processing It can be realized by using (Unit). However, in this method, since the transmission signal is once buffered by the CPU, a delay time occurs in the processing, and there is a possibility that normal control cannot be realized.

  In addition, as a general method for monitoring the signal state, there is a method in which an LED (Light Emitting Diode) is turned on, blinking, or turned off, but in a normal RS-232C device, when the data mark is “1” state. Therefore, it is difficult to confirm (detect) the connection state other than the data communication state (idle state).

  RS-232C uses two control signal lines “CTS” (Clear to Send) and “RTS” (Request to Send) in addition to the data signal lines for hardware flow control. Furthermore, if you try to implement hardware flow control using a relay device that transmits differential signals, the number of control signal lines to be used increases. A LAN cable (UTP cable: Unshielded Twisted Pair Cable: 4 pairs) could not be used.

(Object of the present invention)
An object of the present invention is a system for transmitting an RS-232C signal between relayed RS-232C devices between remote RS-232C devices, where some communication failure occurs in one line segment, and both RS- RS-232C signal remote transmission system that can acquire information on the signal status of the remote line segment from the other line segment when communication between 232C devices becomes impossible, and its use It is to provide a transmission relay device.

Means taken by the present invention to solve the above problems are as follows.
The present invention
A system that transmits RS-232C signals between a higher-level device and a lower-level device that are remote RS-232C devices,
Wherein the transmission relay device of the monitoring side, a transmission relay device of the monitored side, a cable connecting the RS-232C port to each other with the upper side equipment the monitoring side of the transmission relay apparatus, and the monitoring side transmission repeater under a cable for connecting the extension side port between the transmission relay device of the monitoring side, a cable connecting the RS-232C port to each other of the transmission relay device the monitored side and the lower side device,
The transmission relay device on the monitoring side is
A signal converter that converts RS-232C signals and RS-422 signals to each other;
A monitoring state notification unit for transmitting a monitoring mode signal which is a data signal ;
A signal state display unit for displaying the signal state of the segments of the lower device side,
With
The monitored transmission relay device is:
A signal converter that converts RS-232C signals and RS-422 signals to each other;
Upon detecting said monitor mode signal sent from the transmission relay device of the monitoring side, a signal state notifying unit for sending a data signal indicating a signal state of the segments of the lower device side to the monitor side transmission repeater,
With
Preliminarily defining a minimum data rate of a data signal indicating a signal state of a segment on the lower device side sent from the signal state notification unit of the monitored transmission relay device to the monitoring transmission relay device; When the data mark state, which is the state of the data signal of the RXD signal line of the RS232C cable or RS422 cable for the time, continues, the connection state is detected, and the connection state is detected.
RS-232C signal remote transmission system.

The present invention
A control signal that transmits the RTS / CTS signal, which is a control signal transmitted between the monitoring transmission relay device and the monitored transmission relay device, as a single-ended signal, and transmits and receives that the lower-level device is active DTR / DSR signal transmission that is
The RS-232C signal remote transmission system according to claim 1.

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(Function)
The operation of the RS-232C signal remote transmission system according to the present invention will be described. In addition, here, each constituent element used in the description is assigned in correspondence with a reference numeral given to each part in the embodiment to be described later, but this reference sign is only for easy understanding of the contents, The meaning of each constituent element is not limited to each of the above parts.

  According to the RS-232C signal remote transmission system, a data signal and a control signal are separately provided as signals on the extension side, and in the monitoring state, for example, high-speed clock information that is not used in the communication state is transmitted to the control signal. Including the monitored transmission relay device (2) by confirming that the remote transmission relay device (2) has entered the remote monitoring state and returning data of multiple frequencies different from the communication state in order to notify the state The status of the line segment (RS-232C status) and the signal status on the extension side can be identified by the monitoring transmission relay device (1).

  In addition, as a method for confirming the signal state, a method of identifying by changing the lighting time of the display LED of the monitoring transmission relay device (1), or an interface that enables connection with a monitoring device using IP. There is a method of making it possible to monitor from a remote monitoring device.

  In applications such as FA, fine control is realized by frequently exchanging data with a short control time, but if you try to implement it via the CPU to realize the monitoring function, the time for conversion will be However, according to the system of the present invention, remote monitoring can be performed with high response by a simple method without affecting the transmission data as described above.

  In order to monitor the connection status of the RS-232C signal and the RS-422 signal on the extension side, the data space “0” is continuous during idle, but the data space “0” state is assumed during asynchronous communication. Since the data mark “1” state is repeated, the minimum speed of the data rate is specified in advance, and even if the data mark “1” state for that time continues, it is determined that the connection state is established. The connection status of devices can be monitored.

Various control signals (CTS / RTS / DSR / DTR) are set to realize hardware flow control with RS-232C signals, but all control signals are differential to extend RS-232C signals. As the number of control signal lines required increases, the RTS / CTS signal, which is the control signal, is transmitted as a single-ended signal, and the DTR / DSR signal, which is the control signal that transmits / receives that the lower-level device is active Changed the signal reception status on the RS-232C side and RS-422 side to become active and did not transmit the signal.
As a result, transmission of signals between each transmission relay device (1, 2) can be performed with a relatively small number of signal lines, and the transmission relay device can be used with a widely used LAN cable (UTP cable). The transmission distance using (1,2) can be extended.

  The present invention is a system for transmitting an RS-232C signal between relayed RS-232C devices between remote RS-232C devices, where some communication failure occurs in one line segment, and both RS-232C devices RS-232C signal remote transmission system and transmission used for it, which can acquire the signal status information of the remote line segment from the other line segment when communication between them becomes impossible A relay device can be provided.

The conceptual diagram which shows the structure of the RS-232C signal remote transmission system which concerns on this invention. It is explanatory drawing which shows the external appearance of the transmission relay apparatus which concerns on this invention, (a) is a front view, (b) is a top view, (c) is a rear view. The block diagram of the monitoring transmission relay apparatus. The block diagram of the monitored transmission relay apparatus. The block diagram of the signal detection part by the side of RS-232C of a transmission relay apparatus. The block diagram of the signal detection part by the side of RS-422 of a transmission relay apparatus. Explanatory drawing which shows the circuit structure of the RS-232C side and extension side of a transmission relay apparatus. Explanatory drawing which shows the circuit structure of RS-232C signal remote transmission system.

  The present invention will be described in detail based on the embodiments shown in the drawings.

Please refer to FIG.
The RS-232C signal remote transmission system S includes a monitoring transmission relay device 1, a monitored transmission relay device 2, a cable 3 for connecting the monitoring transmission relay device 1 and the upper RS-232C device 6, and a monitoring transmission relay. It comprises a cable 4 for connecting the apparatus 1 and the monitored transmission relay apparatus 2, and a cable 5 for connecting the monitored transmission relay apparatus 2 and the lower RS-232C device 7.

  In this embodiment, the case where the upper RS-232C device 6 is a DCE device and the lower RS-232C device 7 is a DTE device will be described as an example. However, both may be DCE devices. In some cases, both are DTE devices.

With reference to FIG. 2, the external structure of the monitoring transmission relay apparatus 1 will be described.
The monitoring-side transmission relay device 1 includes an RS-232C port 11, an RS-232C port status display LED 12, an extension port 13, and an extension port status display LED 14 on the front of the case 10. Further, a CTS changeover switch 15 and a monitoring setting switch (Remote State Mode Switch) 16 are provided next to the RS-232C port 11 (see FIG. 2A).

  On the upper surface of the case 10, an RS-232C port status display LED 12a and an extension port status display LED 14a are provided. The RS-232C port status display LED 12 a displays the same as the RS-232C port status display LED 12, and the extension port status display LED 14 a displays the same as the extension port status display LED 14. Reference numeral 17 denotes a power indicator lamp (see FIG. 2B).

  A rack mount connector 18 and a DC jack 19 are provided on the back of the case 10 (see FIG. 2C). A monitoring device (not shown) having an interface using IP (Internet Protocol) can be connected to the rack mount connector 18. As a result, a communication failure can be monitored and detected from the monitoring device via the IP network.

  The monitored transmission relay device 2 has the same external structure as the monitoring transmission relay device 1, but the polarity of the input / output interface is different. Each transmission relay device of the monitoring transmission relay device 1 and the monitored transmission relay device 2 is properly used depending on whether the RS-232C device to be connected is a DTE device or a DCE device.

With reference to the block diagram of FIG. 3, the control part of the monitoring transmission relay apparatus 1 is demonstrated.
Reference numeral 101 denotes a high-speed clock generation unit that generates a clock signal used for a monitoring mode signal for informing the monitored transmission relay apparatus 2 that the monitoring transmission relay apparatus 1 is in a monitoring state. These are signal switching units constituting a signal conversion unit, and a monitoring state notification unit is configured by these.
Reference numeral 103 denotes a DPLL (Digital Phase Lock Loop) for analyzing a plurality of response signals transmitted from the monitored transmission relay apparatus 2 and detecting a signal change portion. Reference numeral 104 denotes a counter for measuring the frequency.

The high-speed clock creation unit 101 creates a signal whose clock frequency is higher than that of the internal transmission signal so that it can be identified from the actual data on the monitored transmission relay device 2 side to be monitored. RTS signal is transmitted when it is detected.
Further, the monitoring-side transmission relay device 1 monitors the clock frequency of the CTS signal when entering the monitoring state, and detects the signal state of the lower-level RS-232C device 7 which is a remote device. The detection result is expressed by notifying the monitoring LEDs connected to the display LEDs 12, 12 a, 14, 14 a and the rack mount connector 18. The display method using the display LEDs 12, 12a, 14, and 14a is performed by changing the lighting time depending on the state.

With reference to the block diagram of FIG. 4, the monitoring state detection unit and the signal information notification unit of the monitored transmission relay device 2 will be described.
Reference numeral 203 denotes a DPLL for detecting that the monitoring mode signal comes from the RTS signal, and reference numeral 204 denotes a counter for measuring the frequency, and these constitute a monitoring state detection unit. Reference numeral 205 denotes a frequency divider that generates a plurality of different clock signals for notifying the state of the monitored transmission relay apparatus 2 side, and reference numeral 202 denotes a signal switching unit, which is a signal information notification unit. Parts.

  The monitored transmission relay device 2 detects that the monitoring transmission relay device 1 has entered the monitoring state when it detects a clock signal having a frequency higher than the actual data in the RTS signal, and the RS-232C connection state And a plurality of different clock signals for transmitting the control signal status of RS-232C are generated by the frequency divider 205 and transmitted to the monitoring transmission relay device 1.

With reference to FIG. 5, the signal detection unit on the RS-232C side of the transmission relay apparatuses 1 and 2 will be described.
The signal detector on the RS-232C side includes a comparator 105 for detecting -15V to -3V, which is the data mark "1" state of the RS-232C signal, and + 3V to + 15V, which is the data space "0" state. RS-232C receiver 106 for detecting.

  As described above, the signal detection unit on the RS-232C side detects the data mark “1” state by the comparator 105 and the data space “0” state by the RS-232C receiver 106. The data mark “1” signal detected by the RS-232C receiver 106 is continuously output for a certain period of time in the communication state so that the signal reception state is not canceled. The RS-232C signal can be detected by ORing the two kinds of signals of this signal and the data mark “1” signal detected by the comparator 105.

The signal detection unit on the RS-422 side of the transmission relay apparatuses 1 and 2 will be described with reference to FIG.
The RS-422 signal detector on the extension side receives the RXD + / RXD- signals that are input signals from the RS-422 receiver in order to detect the data mark “1” state and data space “0” state of the differential signal. The RS-422 signal can be detected by ORing the two types of signals in the normal state and +/- state.

  Note that if the data mark “1” state and the data space “0” state take a long time to fluctuate, a glitch (noise due to contact failure appearing in the electronic circuit) is generated, which is the same as the RS-232C side. The counter 108 maintains the signal state (the time constant can be calculated from the rise / fall of the minimum baud rate) and then OR is performed.

With reference to FIG. 7, the circuit configurations of the RS-232C side and the extension side of the transmission relay apparatuses 1 and 2 will be described.
RS-232C signals include CTS / RTS signals as control signals. These signals are not differentiated on the extension side, and even if they are transmitted as RS-232C signals, signal fluctuations are small, so remote transmission (transmission over long distances) is possible without problems. Therefore, transmission is possible by once converting the CTS / RTS signal to a TTL (LVTTL) level which is a single-ended signal using an RS-232C level conversion IC and then converting it again to an RS-232C signal.

In addition, the DTR / DSR signal becomes active when the RS-232C signal enters the transmission state, so it must be activated when the RS-232C signal reception state is detected and the RS-422 signal is detected. Thus, signal lines for transmission can be reduced.
Specifically, for single-ended signal transmission, the number of signal lines to be used may be n + Gnd lines, but for differential signal transmission, 2n + Gnd lines are required, and simple differential signals are used. The number of necessary signal lines increases.

Therefore, in the present embodiment, the data signal that requires high-speed transmission is differentiated into an RS-422 signal, and the CTS / RTS signal that is a low-speed (1/10 times the data signal) control signal is RS Even if the -232C signal is transmitted as it is, it can be transmitted remotely, so it is not differentiated.
Furthermore, for the DTR / DSR signal that transmits / receives that the RS-232C device 7 on the lower side is activated, the signal comes from each terminal / modem in the RS-232C signal detection circuit and RS-422 signal detection circuit. The DTR / DSR signal is not transmitted, so that it can be detected.

  This enables remote transmission of RS-232C signals via a total of 7 signal lines: 4 for data signals + 2 for control signals + 1 for Gnd. Therefore, a normal LAN cable (UTP cable) can be used. The connection you used is now possible.

Next, the signal flow of the RS-232C signal remote transmission system S will be described with reference to FIG.
During normal data transmission, the RTS signal is converted from a RS-232C signal to a TTL (Logic) signal and then converted back to a 232C signal for remote transmission.
The TXD signal, which is a high-speed data signal, is converted from an RS-232C signal to a TTL signal and then converted to an RS-422 signal, which is a differential signal, for remote transmission.

The RTS signal is received as a CTS signal in the monitored transmission relay device 2 on the receiving side, converted from an RS-232C signal to a TTL signal, and then converted to an RS-232C signal so that the RS-232C device can recognize it again. .
The TXD signal is received as an RXD signal in the monitored transmission relay device 2 and converted from an RS-422 signal to a TTL signal and then converted to an RS-232C signal so that the RS-232C device can recognize it. As a result, remote transmission of data signals and control signals (CTS / RTS signals) can be performed.

Next, the function of monitoring the signal state on the remote side on the monitoring transmission relay device 1 side will be described.
First, when the monitoring setting switch 16 of the monitoring transmission relay device 1 is turned on, the monitoring transmission relay device 1 that performs monitoring from the monitoring transmission relay device 1 side displays a remote monitoring status notification circuit (monitoring status notification unit shown in detail in the upper part of FIG. The monitoring mode signal for notifying that the remote monitoring state is established is transmitted to the monitored transmission relay device 2 side using the RTS signal. Even during monitoring using the control signal line, the data signal can be transmitted without any problem.

When the monitored transmission relay device 2 that has received the monitoring mode signal as a CTS signal is detected by the remote monitoring status notification signal detection circuit (configured by the monitoring status detection unit) shown in detail in the upper part of FIG. Stop transmission of CTS / RTS signal. Then, a response signal, which is information on the signal state of the line segment including the lower-level RS-232C device 7 created by the remote status answer signal creation circuit shown in detail in the lower part of FIG. 8 , is sent to the monitoring transmission relay device 1 side. Transmit using RTS signal.

  The monitoring transmission relay apparatus 1 that has received it as a CTS signal detects the signal state of the monitored transmission relay apparatus 2 side, which is the remote side, by the remote state signal detection circuit shown in detail in the lower part of FIG. Signal transmission to the display LEDs 12, 12a, 14, 14a and the monitoring device is performed.

  In the present embodiment, the RS-232C port status display LED 12 of the monitoring transmission relay device 1 includes the monitoring transmission relay device 1, the monitored transmission relay device 2, the upper RS-232C device 6, and Lights up when the lower-level RS-232C device 7 is linked up and flashes during communication. Also, during monitoring, it lights up when the link with the RS-232C port status LED 12 on the opposite side (monitored transmission relay device 2 side) is up, blinks slowly when the RTS signal from the opposite side is OFF, and the opposite RS Flashes rapidly when the link with the -232C port status LED 12 is down. The opposite RS-232C port status LED 12 lights up when data is transmitted / received.

  Further, the extended port status display LED 14 of the monitoring transmission relay device 1 is lit when the devices 1, 2, 6, and 7 are linked up in a normal state, and flashes rapidly during communication. During monitoring, it lights when the link with the extension port status display LED 14 on the opposite side is up. The extension port status display LED 14 on the opposite side blinks slowly when monitored. Note that the blinking mode is not limited to this, and can be set as appropriate.

  The remote monitoring state is released by turning off the monitoring setting switch 16 on the monitoring transmission relay device 1 side. The signal state is detected using the circuit shown in FIG. 5 for the signal on the RS232C side and the circuit shown in FIG. 6 for the signal on the RS422 side.

  The terms and expressions used in this specification are merely explanatory and are not limiting at all, and exclude terms and expressions equivalent to the features described in this specification and parts thereof. There is no intention to do. It goes without saying that various modifications are possible within the scope of the technical idea of the present invention.

S RS-232C signal remote transmission system 1 Monitoring transmission relay device 10 Case 11 RS-232C port 12 RS-232C port status display LED
12a RS-232C port status LED
13 Extension port 14 Extension port status LED
14a Extension port status indicator LED
15 CTS selector switch 16 Monitoring setting switch 17 Power indicator 18 Rack mount connector 19 DC jack 101 High-speed clock generator 102 Signal selector 103 DPLL
104 Counter 105 Comparator 106 RS-232C Receiver 107 Counter 108 Counter 2 Monitored Transmission Relay Device 202 Signal Switching Unit 203 DPLL
204 Counter 205 Divider 3 Cable 4 Cable 5 Cable 6 Upper RS-232C device 7 Lower RS-232C device

Claims (2)

A system that transmits RS-232C signals between a higher-level device and a lower-level device that are remote RS-232C devices,
Wherein the transmission relay device of the monitoring side, a transmission relay device of the monitored side, a cable connecting the RS-232C port to each other with the upper side equipment the monitoring side of the transmission relay apparatus, and the monitoring side transmission repeater under a cable for connecting the extension side port between the transmission relay device of the monitoring side, a cable connecting the RS-232C port to each other of the transmission relay device the monitored side and the lower side device,
The transmission relay device on the monitoring side is
A signal converter that converts RS-232C signals and RS-422 signals to each other;
A monitoring state notification unit for transmitting a monitoring mode signal which is a data signal ;
A signal state display unit for displaying the signal state of the segments of the lower device side,
With
The monitored transmission relay device is:
A signal converter that converts RS-232C signals and RS-422 signals to each other;
Upon detecting said monitor mode signal sent from the transmission relay device of the monitoring side, a signal state notifying unit for sending a data signal indicating a signal state of the segments of the lower device side to the monitor side transmission repeater,
With
Preliminarily defining a minimum data rate of a data signal indicating a signal state of a segment on the lower device side sent from the signal state notification unit of the monitored transmission relay device to the monitoring transmission relay device; When the data mark state, which is the state of the data signal of the RXD signal line of the RS232C cable or RS422 cable for the time, continues, the connection state is detected, and the connection state is detected.
RS-232C signal remote transmission system. A control signal that transmits the RTS / CTS signal, which is a control signal transmitted between the monitoring transmission relay device and the monitored transmission relay device, as a single-ended signal, and transmits and receives that the lower-level device is active DTR / DSR signal transmission that is
The RS-232C signal remote transmission system according to claim 1.

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