JPS6119190B2 - - Google Patents

Description

Detailed Description of the Invention The present invention connects a plurality of slave stations and a master station in common through a pair of transmission lines, and applies a DC voltage between the lines of the transmission lines from a power supply provided in the master station through a resistor. Regarding the data transmission method, in which the encoded data is transmitted by short-circuiting the lines of the transmission line according to the data using a switching element connected between the lines at each station, This system automatically sequentially inspects each slave station to detect and eliminate short circuits between transmission lines due to failures in switching elements, etc.

As an example of this type of data transmission system, the configuration shown in FIG. 1 can be considered. Here, 1 is a master station that controls the entire data transmission system, 2-1, 2-2,
......, 2-n is a slave station as a controlled terminal, 3 and 4 are a pair of signal lines that commonly connect the master station 1 and n slave stations 2-1 to 2-n, and 5 is a slave station. This is a power supply auxiliary line. The master station 1 has a clock generating circuit 6, and its output clock pulse is amplified by an output amplifier consisting of an output transistor TR ₀ and resistors R ₀ and R ₁₀ and then sent to signal lines 3 and 4. Vs is the master station power supply.
The slave stations 2-1 to 2-n are all configured in the same way. For example, the slave station 2-1 includes a receiving/transmitting circuit 7 and a signal exchange between the receiving/transmitting circuit 7 and the signal lines 3 and 4. A light-emitting element that performs this, such as a light-emitting diode LED
and a photodetector, such as a phototransistor PTr,
Phototransistor PTr output amplification transistor
It has an operational amplifier OP that detects incoming signals from the Tr and signal lines 3 and 4. In the slave station 2-1, R ₁ to _{R 8} are resistors, C ₁ is a capacitor, D ₁ to _{D 3} are diodes,
AC is an alternating current power terminal.

Note that the number n of slave stations 2-1 to 2-n can be increased until transmission and reception are no longer possible due to the influence of the resistance of the signal lines 3 and 4, and it is usually easy to set n to about 100 stations. . However, as the number of slave stations increases, for example, the signal level decrease that occurs in the signal line resistance due to the signal current flowing through the termination resistor _R8 in slave station 2 increases, and the signal transmission transistor Tr in the slave station far from the master station increases. In addition to the fact that the master station cannot detect the on state of the terminal, making it difficult to transmit data from the slave station as described below, due to the drop in signal line voltage at the slave station mentioned above, Another problem arises in that the charging voltage of the capacitor C, which is charged by the signal line voltage via the diode _D2 , decreases, making it difficult to detect data transmitted from the master station.

Next, FIG. 2 shows an example of the signal waveform of the data signal transmitted from the master station in the data transmission section described above. In the configuration shown in FIG. 1, it is assumed that a DC voltage of, for example, 24 V is constantly supplied to the signal line 3 from the DC power supply Vs of the master station 1 via the resistor _R0 , and in this state, the In order to transmit the data signal having the waveform _shown in FIG. short-circuit between 1st
The data signal transmitted in the illustrated system is
As shown in Figure 2, 1, 0 or 2 of H, L
A binary data signal is expressed as a value signal, with H indicating a long ON or conductive time width of the output transistor _TR0 , and L indicating a short time width. This data signal is transmitted from the master station 1 to all slave stations 2-1 to
2-n simultaneously. In the slave station that receives this, the terminal voltage appearing at the terminating resistor _R8 connected between the signal lines 3 and ₄ is guided to the operational amplifier OP via _the resistor _R3 , The data signal waveform shown in Figure 2 is detected in the form of a difference from a set constant voltage value, and in response to a short circuit between signal lines 3 and 4, for example, a light emitting diode LED is turned on to convert it into an optical signal. light emitting diode
The blinking state of the LED is transmitted to the receiving/transmitting circuit 7, and a data signal is guided. The receiving/transmitting circuit 7 can be configured by, for example, a microcomputer, and analyzes the received and converted data signal, and determines whether the address specified by the specific slave station attached to the data signal matches or does not match the slave station address. However, if the addresses match, the content of the subsequent data, such as data transmission control information, is detected. Note that the receiving/transmitting circuit 7 not only receives such data but also prepares to transmit data to be responded to data transmission control information from the master station 1. The type of data responded from each slave station differs depending on the purpose of data transmission, but in so-called hotel vendor systems, data on the number of products sold in vending refrigerators and data on the number of refrigerators inside are contact information and operation information. , in an automatic measurement system, is measured quantity data. A slave station, for example slave station 2-1, which has been given an address by master station 1, forms a data signal to be responded to, for example, as shown in FIGS. 3A to 3C.

That is, the slave station 2-1 receives the address signal from the master station 1 at regular time intervals following the above-mentioned address signal. A clock pulse train having a waveform as shown in FIG. 3A is detected, and in synchronization with the clock pulse train, H and L are determined depending on the presence or absence of a pulse having a wider pulse width than the clock pulse, as shown in FIG. 3B. A binary data signal is formed as shown in FIG.
Send to. That is, such a binary data signal for stress is passed through the form of an optical signal to a phototransistor.
PTr, and controls the on/off of the phototransistor PTr, and when the response data signal waveform shown in Figure 3B is at a high level, the transmitting transistor
The Tr is turned on, that is, made conductive to short-circuit the signal lines 3 and 4. The time width of the line-to-line short circuit for data transmission from the slave station 2-1 is such that the short-circuit state continues for a certain period of time after the clock pulse from the master station 1 is detected, and also before the arrival of the next clock pulse. Turn it off, or open the short circuit. Therefore, when the slave station 2-1 performs the line-to-line short circuit in this manner, the master station 1
As shown in the signal waveform in Figure C, when transmitting the clock pulse train, even if the output transistor TR ₀ is turned off, the transmission transistor of slave station 2-1
When the Tr is in the on state, the signal lines 3 and 4 are short-circuited through the resistance of the signal line, so the signal line voltage appearing at the output terminal of the output transistor TR ₀ in the master station 1 is not fully recovered,
At the same time as the transmission transistor Tr in the slave station 2-1 returns to the off state, the line voltage value is restored to the original line voltage value. Moreover, when the response data signal waveform from slave station _2-1 is the L signal shown in FIG. At the same time, the signal line voltage appearing at the output terminal also recovers to its original line voltage value. Therefore, the master station 1 can receive the response data signal from the slave station 2-1 by monitoring the relationship between the signal line voltage and the on/off state of the output transistor _TR0 . can.

Note that the only slave station that transmits such a response data signal is the slave station designated by the address signal from master station 1, and it is up to each slave station whether or not to transmit response data in response to the reception of that address signal. Station 2-
It is monitored and controlled by the receiving and transmitting circuit 7 in 1 to 2-n. In order to ensure and easily monitor and control the receiving/transmitting circuit 7, a fixed time interval is provided between the address designation and control command signal from the master station 1 and the clock pulse train for transmitting a response from the slave station. , data transmission is carried out repeatedly, with the period of the signal train separated by such fixed intervals, that is, the period of transmission at the master station 1 and the reception following that transmission, as one unit of data transmission period. For example, in a hotel vendor system, product sales data from vending machines placed in each guest room is sequentially collected. In addition, each slave station 2-1~
In 2-n, even if a transmission signal is received from master station 1, unless a clock pulse train for transmitting response data is received within a certain period of time, the response data signal is not transmitted and the reception is stopped. It will continue to be in a standby state.

However, since the signal transmission lines 3 and 4 in the data transmission system of this type are several kilometers long, various surge voltages such as surge voltages due to electrical induction and surge voltages induced from power wiring are applied to the signal transmission lines 3 and 4.
4 is easy to invade. In order to cope with the intrusion of such surge voltage, it is customary to insert a circuit element for suppressing surges between the transmission lines, as will be described later. Therefore, in this type of data transmission system, the surge suppression circuit element inserted between the transmission lines 3 and 4 remains short-circuited due to the intrusion of surge voltage, and the output transistor at the master station remains short-circuited. There is a high possibility that the transmission lines 3 and 4 may remain short-circuited due to damage to the transmitting transistor in the slave station or the transmitting transistor in the slave station, making it impossible to perform data transmission in the manner described above. In order to eliminate such line-to-line short circuit faults between the signal lines 3 and 4, it is first necessary to check whether or not there is a failure in the terminal circuit elements of each station and detect the failure location. For example, in a so-called hotel vendor system that performs transmission, the signal lines 3 and 4 are wired within the walls of the building, and each slave station is distributed in each guest room, so the terminals at each slave station are It is a task that requires an extremely large amount of labor and time to sequentially disconnect and inspect circuit elements from the signal lines 3 and 4. Therefore, in the conventional data transmission system of this type, the above-mentioned The drawback was that it was extremely difficult to maintain reliability by immediately eliminating short-circuit faults.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks, to automatically inspect terminal circuit elements at each station in the event of a short-circuit fault between signal transmission lines, and to facilitate the detection of a faulty location. An object of the present invention is to provide a data transmission system with an automatic inspection function that can maintain reliability by isolating and eliminating failure points.

That is, in the data transmission system of the present invention, a plurality of slave stations and a master station that manages the slave stations are commonly connected by a pair of signal lines to which a DC voltage is applied between the lines from a power supply via a resistor. The data is encoded and transmitted by driving switching elements inserted between the signal lines in the master station and the plurality of slave stations in accordance with the data to short-circuit the signal lines. In the data transmission method, each of the plurality of slave stations is provided with a switching means in series with a circuit portion related to the switching element that short-circuits between the signal lines when selected, and the signal line is connected for a predetermined length of time. When the short-circuit continues beyond the limit, the switch means in all of the plurality of slave stations are once opened, and then the switch means in the plurality of slave stations are sequentially closed under control from the master station. Accordingly, it is possible to detect a short-circuit failure between signal lines caused by a circuit portion related to the switching element.

The invention will be explained below by way of example embodiments with reference to the drawings.

An example in which the configuration of the slave stations 2-1 to 2-n in the conventional data transmission system of this type shown in FIG. 1 is improved according to the present invention will be described with reference to FIG. 4. In this configuration, in addition to the conventional configuration shown in FIG. 1, a signal resistor R ₈ is installed between the signal lines 3 and 4 as a surge voltage suppressing circuit element.
A time constant circuit is constructed by connecting a filter capacitor C ₂ in parallel with the zener diode,
ZD ₁ , ZD ₂ and direct resistor R ₉ are additionally connected. As mentioned above, in the configuration of the slave station shown in FIG. In order to disconnect the connection between the signal lines of the suppressing Zener diode and easily inspect those circuit elements, connect one end of those circuit elements together to the transmission line via relay contact RLb. It has been done. The relay RL that drives the opening and closing of the relay contact RLb is connected to the transmitting/receiving circuit 7 and is configured to be controlled by the transmitting/receiving circuit 7, as will be described later. However, the relay contact
RLb is always kept closed during normal data transmission so that it can perform the functions of data transmission from the slave station and surge voltage suppression.

Therefore, as mentioned above, even when encoded data is being transmitted due to a short circuit between the signal lines 3 and 4, or when data transmission is stopped,
If the signal lines are short-circuited for a certain period of time, for example 0.5 seconds or more, it is assumed that the terminal circuit element in one of the slave stations has failed and the signal lines are short-circuited. The receiving/transmitting circuit 7 in each slave station operates the relay RL, and all the relay contacts RLb in each slave station are opened at once. In such a state, even if there actually is a faulty circuit element that short-circuits the signal lines in one of the slave stations, it will be disconnected from the signal lines, so data transmission from at least the master station 1 will be possible. . In this state, specify the address from the master station 1 and sequentially close the relay contacts RLb in each slave station 2-1 to 2-n.
If there is a slave station that becomes short-circuited again due to the closing of RLb, the slave station is returned to a normal data transmission state with only its relay contact RLb open. In addition, in the slave station where the failure occurred, relay contact RLb
When the terminal is opened, data transmission from the slave station is disabled, but normal operation is possible, and the malfunctioning part can be repaired separately during that time. It should be noted that when the failure point is not found even through the sequential inspections according to the commands from the master station 1 mentioned above, or after a predetermined period of time, for example,
After 10 minutes have passed after the occurrence of the line-to-line short-circuit fault, it is determined that the previous line-to-line short-circuit fault was caused by a temporary failure of the terminal circuit element of one of the slave stations due to surge voltage, etc., and each Relay contact RLb shall be automatically closed for each station to return to normal state. In the data transmission system with the configuration shown in Figure 1, the most likely cause of the above-mentioned short-circuit failure between signal lines is the Zener diode for surge suppression in the configuration of each slave station shown in Figure 4. ZD ₁ , ZD ₂ and the transmission transistor Tr, and other circuit elements can be considered to have an extremely low possibility of causing a line-to-line short circuit failure. Therefore, the Zener diodes ZD ₁ and ZD ₂ and the transmitting transistor in one of the slave stations
If one of the Tr's fails and becomes permanently conductive, the signal lines will be constantly short-circuited, and the entire data transmission system will stop functioning. However, if the relay contact RLb at the slave station is open, Only the surge suppression and data transmission functions of the slave station are stopped, and all other functions in the data transmission system can be performed as usual. Therefore, as mentioned above, the relay contact of the slave station
It is possible to continue normal operations with RLb open, repair the failure, and temporarily use other appropriate data transmission means for data transmission from the slave station.

Next, the transmission line line voltage waveform and relay contact RLb
The temporal relationship between the opening and closing states is shown in FIGS. 5A to 5D, respectively. Under normal data transmission conditions, the voltage between the signal lines is intermittently short-circuited for extremely short periods of time, but in the case of a failure in the terminal circuit element of the slave station, as shown in Figure 5A, for example, A short-circuit condition occurs after an extremely long period of time _T1 , such as 0.5 seconds. When this continuous line-to-line short circuit condition is detected at each slave station, the relay contact RLb of each slave station automatically becomes open as shown in Figure 5D. a certain period of time such as
After T ₂ has elapsed, the normal closed state is automatically restored. However, during that time, the terminal circuit element of the slave station that caused the line-to-line short fault has been in a faulty state since the beginning of time _T1 , as shown in Figure 5C, so the relay contact RLb of the slave station As shown in FIG. 5B, the chisel maintains the open state even after time _T2 has elapsed by command from the master station. When the relay contacts RLb of each slave station are opened all at once, the short-circuited state of the signal lines is at least temporarily eliminated, so the normal state where data transmission is possible is restored as shown in Figure 5A. .

Furthermore, even if a failure in the terminal circuit element in one of the slave stations is discovered as described above and only the relay contact RLb in that slave station is left open, if a short-circuit fault between signal lines remains, Since there is another faulty terminal circuit element in another slave station, the above-mentioned automatic inspection using the address from the master station is continued to discover and discover the other faulty terminal circuit element. Elimination will be performed in the same manner as described above.

It goes without saying that the master station, like each slave station, detects a continuous short-circuit condition between lines and issues an automatic check using the sequential addresses mentioned above. If the problem is due to other causes such as contact between the signal lines themselves, disconnection, or power outage, the automatic inspection process described above will not be able to detect the cause of the failure, and therefore it will be impossible to return to normal conditions. Although this is impossible and other measures must be taken, it is relatively easy to discover and eliminate failures in the master station itself. Note that the relay contacts for disconnecting the terminal circuit elements mentioned above can be replaced with semiconductor switches with high surge resistance and extremely low probability of failure.Also, when using relays, the driving power source for the relays is commercial AC power supply. It is also possible to provide the receiving and transmitting circuit 7 of each slave station with a monitoring function to avoid battery consumption during a power outage.

As is clear from the above description, according to the present invention, it is possible to automatically cope with the occurrence of a short-circuit failure between signal lines in a data transmission system in which data is encoded and transmitted due to a short-circuit between signal lines. After temporarily maintaining the signal line in a state where the line-to-line short circuit fault has been eliminated, it is possible to sequentially automatically check and detect the cause of failure due to the terminal circuit element at each station. The time during which the entire data transmission system is stopped can be significantly reduced.

The automatic inspection of data transmission systems according to the method of the present invention can be similarly applied to transmission systems using one or more pairs of signal transmission lines, and can also be applied to transmission systems using data transmission methods other than pulse width modulation. can do.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the configuration of a data transmission system according to the present invention, FIG. 2 is a waveform diagram showing an example of the data transmission waveform from the master station, and FIG.
B and C are waveform diagrams sequentially showing the process of data transmission from the slave station, Figure 4 is a circuit diagram showing a detailed example of the configuration of the slave station, and Figure 5 A, B, C,
Similarly, D is a time chart showing the process of checking for signal line faults. 1... Master station, 2-1 to 2-n... Slave station, 3, 4
... Signal line, 5 ... Power supply auxiliary line, 6 ... Clock generation circuit, 7 ... Receiving and transmitting circuit, TR ₀ ... Output transistor, OP ... Operational amplifier, LED ... Light emitting diode, PTr ... Photo Transistor, Tr…
... Transmission transistor, R ₀ , R ₁ to R ₁₀ ... Resistor,
C ₁ , C ₂ ... Capacitor, D ₁ to _{D 3} ... Diode, ZD ₁ , ZD ₂ ... Zener diode, RL ...
Relay, RLb...Relay contact.

Claims (1)

[Scope of Claims] 1 A plurality of slave stations and a master station that manages the slave stations are commonly connected by a pair of signal lines to which a DC voltage is applied between the lines from a power supply via a resistor, and the master station and data in which the data is encoded and transmitted by driving a switching element inserted between the signal lines in each of the plurality of slave stations according to the data to short-circuit the signal lines. In the transmission method, each of the plurality of slave stations is provided with a switching means in series with a circuit part related to the switching element that short-circuits between the signal lines when selected, and the signal lines are short-circuited for a predetermined length of time. When short-circuited continuously for a period exceeding 1, the switch means in all of the plurality of slave stations are once opened, and then the switch means in the plurality of slave stations are sequentially closed under control from the master station. A data transmission system with an automatic inspection function, characterized in that a short-circuit failure between signal lines caused by a circuit portion related to the switching element can be detected. 2. In the data transmission system according to claim 1, the switch means in all of the plurality of slave stations is closed after an inspection period of a predetermined length has elapsed after the occurrence of the short-circuit fault between the signal lines. A data transmission system with an automatic inspection function.