JP2507635B2 - Redundant bus system data transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention is a duplex system in which each station is connected to a two-system bus line and the data transmission timing of each station is controlled by a token bus system. The present invention relates to a bus type data transmission device.

(Prior Art) In a LAN (Premises Information Communication Network), in order to ensure reliability of data transmission, as shown in FIG. 3, terminal numbers ST ₁ , ST ₂ ,
, _N stations 2 with ST _N are connected in parallel. In such a LAN, the token bus system is adopted as a system for controlling the timing at which each station 2 occupies each bus line 1a, 1b when executing data transmission between each station 2. As is well known, this token bus system forms one information ring between each station 2 and circulates a token in the ring, and a station executing data transmission captures the token, Each bus line 1a, 1
Data is transmitted using b. When the data transfer is completed, the token is transferred to the information ring, that is, each bus line.
Release to 1a and 1b.

Further, when the token circulating on the bus lines 1a and 1b disappears, neither station 2 can carry out data transmission. Therefore, each station has a function of monitoring and reproducing the disappearance of the token. Specifically, if the token disappears, data cannot be transmitted, so if the duration of no signal on the bus line continues for a specified time or longer, the token is regenerated and the token is sent out on the bus line. The aforementioned information ring is reconstructed between the stations 2.

The specified time Tm mentioned above is based on the standard (IEEE 802.4, ISO 8
802/4), it is set to a time that is seven times the duration (throttle time) T _S of each throttle that constitutes the frame.

Each station 2 is constructed, for example, as shown in FIG. That is, the received signals input from the bus lines 1a and 1b are demodulated by the demodulators 3a and 3b and the changeover switch 4
Is input to the MAC layer 5 via. The transmission signal sent from the MAC layer 5 is modulated by the modulators 6a and 6b and then sent to the bus lines 1a and 1b.

MAC (Media Access Control Circuit)
The layer 5 controls the transmission timing of the data to be transmitted to the other station 2 transmitted from the upper layer 7 including the control unit for executing various information processing by the token bus method, and transmits the data to be transmitted in the transmission frame. Executes various controls and data processing related to embedded data transmission.

The received signals demodulated by the demodulators 3a and 3b are input to the error detection circuits 8a and 8b, respectively, and to the first-arrival determination circuit 9. Each error detection circuit 8a, 8b checks whether there is an error in the received signal received from each bus line 1a, 1b, and if an error is detected, sends an error detection signal to the bus line selection circuit 10. The first-arrival determination circuit 9 also determines the first-arrival order of the received signals input from the bus lines 1a and 1b, and sends the first-arrival determination result to the bus line selection circuit 10. The bus line selection circuit 10 refers to each input error detection signal and the first arrival judgment result
It is determined whether the received signals from 1a and 1b are applied to the MAC layer 5, and the changeover signal is sent to the changeover switch 4.

That is, when the data is sent from the station 2, it is sent to both bus lines 1a and 1b, but when the data is taken in from each bus line 1a and 1b, the bus line selection circuit 10 receives each received signal. It is judged whether the condition is good or bad, and the received signal having the better reception condition is fetched.

In such a data transmission apparatus, for example, as shown in FIG. 5, a station 2 having a terminal number ST _X (hereinafter abbreviated as station ST _X as necessary) and a bus line 1a.
If the signal line between and is disconnected, the station ST
_The data sent from _X is transmitted to only one bus line 1b. In this case, the other station ST _Y takes in signals from both bus lines 1a and 1b, but the bus line 1a
Since there is no data above, the first-arrival determination circuit 9 determines that the received signal from the bus line 1b is the first-arrival signal,
The bus line selection circuit 10 selects the reception signal from the bus line 1b. Therefore, thereafter, data transmission is performed using the bus line 1b which is sounder.

Even if one bus line 1a is not completely unusable, if noise is mixed in one of the bus lines and many errors occur in the reception signal received via the corresponding bus line, The number of times the error detection signal output from the line side error detection circuit is output per unit time is significantly larger than that output from the sound line side error detection circuit. Select the received signal on the bus line with the fewest.

In this way, by duplicating the bus lines that connect the stations 2 to each other, even if an abnormality occurs in one of the bus lines, the data transmission can be continued using the other bus line. Can be improved.

However, the duplex bus type data transmission device configured as described above also has the following problems to be improved.

That is, as shown in FIG. 6, it is assumed that, in addition to the disconnection failure in the bus line 1a of the station ST _X , the disconnection failure occurs in the other bus line 1b of the other station ST _Y. Note that stations ST _X and ST _Y are 2
It is assumed that it is more than the station away.

In such a state, as shown in FIG. 6, for example, the station S immediately before the station ST _X (upstream)
When T _X-1 captures the token and sends the data, which data is sent to both bus lines 1a, 1b at the same time.
Therefore, station ST _X sends this data to bus line 1b.
Via the bus line 1a, the station ST _Y can receive the same data.

Next, when the station ST _X captures the token emitted by the station ST _X-1 and sends out its own data D _X ,
This data D _X is transmitted only to one bus line 1b, and the corresponding data D _X is not transmitted to the other bus line 1a. Thus, the station ST _Y is the station ST _X data D _X
Is not received, the duration of the data D _X becomes a non-signal state. And the token is the next station ST
_When moving to _{X + 1} and data is sent from this station ST _{X + 1} , this data can be received via the bus line 1a.

However, for example, the duration T _X data D _X in the station ST _X is longer than the specified time Tm that is defined by the standard mentioned above, the station ST _Y, since no signal time lasts the time T _X, token When it is determined that the tokens have disappeared, a token request signal is output to the bus lines 1a and 1b. Note that the token request signal is actually sent only to the bus line 1a. When the token cannot be captured within the predetermined time, the station ST _Y itself sends the token to rebuild the above-mentioned information ring between the stations 2 connected to the bus lines 1a and 1b. .

However, even in the reconstructed information ring, token trapped in the station ST _X, the station ST _X is at the time of sending the data D _X, is executed to rebuild the information ring again at the station ST _Y. Therefore, since this state is repeated forever, unless the cause of the failure is eliminated, not only the failed stations ST _X and ST _Y, but also the data transmission between all stations 2 connected to the two-system bus line becomes impossible. .

(Problems to be Solved by the Invention) As described above, in the conventional data transmission apparatus of the dual bus system, a failure of only one bus line can be sufficiently dealt with, but a plurality of buses different from each other may be used. When the line is broken, there is a problem that the data transmission of the entire data transmission device becomes impossible.

The present invention has been made in view of such circumstances, and when a no-signal state of a received signal exceeds a predetermined time, by forcibly cutting off data transmission from a corresponding station to a bus line, even if a plurality of plural Even if a disconnection occurs between different stations on different bus lines, it is possible to prevent a system down of the entire device, minimize damage, and improve the reliability of the entire device. The purpose is to provide.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention connects each station to each bus line of two system bus lines transmitting the same data, and one bus line. When it becomes impossible to perform data transmission using the other bus line, data transmission is performed using the other bus line, and the timing of sending data to each bus line in each station is controlled by the token bus system, and the token is sent from each station. In a duplex bus type data transmission device capable of reconstructing an information ring by re-transmission, each station is provided with a switch circuit that is inserted in a signal transmission path for a two-system bus line and can disconnect only the signal transmission path. The no-signal continuation time exceeds the predetermined time by measuring the no-signal continuation time in the two-system bus line. And a no-signal state detection circuit that outputs a no-signal signal, and a signal to the switch circuit when the number of outputs of the no-signal signal output from the no-signal state detection circuit reaches a predetermined limit number within a predetermined period. A transmission prohibition control circuit for transmitting a disconnection release signal of the transmission path is provided, and its own signal transmission path is separated from the two-system bus line.

(Operation) In the duplex bus type data transmission device configured as described above, for example, when a disconnection failure occurs in different bus lines in a plurality of stations, the data sent from the station that previously captured the token is sent to the other station. Is not received by. Therefore,
When the duration of the data exceeds a predetermined time, the no-signal state detection circuit in the receiving station outputs a no-signal signal. Then, when the no-signal signal is output a predetermined number of times or more within a predetermined period, signal transmission from the corresponding station is prohibited. Therefore, this station only receives data and stops sending data. Therefore, since the station does not send the token request signal to the bus line, the token information ring reconstruction process is not executed. As a result, the data transmission apparatus continues the data transmission in the state except the station where the signal transmission is prohibited.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of each station 2 incorporated in the duplex bus type data transmission apparatus of the embodiment. The overall configuration of the data transmission device is the same as in FIG. Therefore, the same parts as those in FIGS. 3 and 4 are designated by the same reference numerals, and the description of the overlapping parts will be omitted.

In each station 2 in the data transmission apparatus of this embodiment, as shown in FIG. 1, modulators 6a and 6b for modulating the transmission signal output from the MAC layer 5 and each data bus 1 are provided.
Switch circuits 21a and 21b are respectively inserted between a and 1b. Further, one of the received signals received from the bus lines 1a, 1b is selected by the changeover switch 4, and the selected received signal is input to the MAC layer 5 and the no-signal state detection circuit 22 Is input to.

The no-signal-state detection circuit 22 measures the duration of the no-signal state in the received signal selected by the changeover switch 4, and the no-signal duration is defined by the above-mentioned standard (IEEE 802.4, I
SO 8802/4) exceeds the specified time Tm, which is 7 times the duration (throttle time) T _S of each throttle that composes the frame specified by SO 8802/4) Send to 23. This transmission prohibition control circuit
23 performs various calculations on the input signal-less signal and sends the calculation results as an open / close control signal to the switch circuits 21a, 21b.

FIG. 2 is a block diagram showing a schematic configuration of the transmission prohibition control circuit 23. The pulsed signalless signal output from the no-signal state detection circuit 22 is input to each of the filter circuits 24 and 25. _A predetermined period T _A and a limit number of times n ₁ are externally applied to the filter circuit 24 as parameters. The predetermined period T _A and the limit number of times n ₁ can be changed as needed. Then, when the signal-less signal is input at the limit number n ₁ times or more within the predetermined period T _A , the filter circuit 24
Applies an H level set signal to the set terminal S of the next flip-flop 26. Therefore, an open signal of H level is sent from the output terminal Q of the flip-flop 26. When the H level open signal is sent from the transmission prohibition control circuit 23, the switch circuits 21a and 21b are opened.

Note that the predetermined time T _A is set to a time that is significantly longer than the specified time T m. However, if it is too long,
When the output of each station 2 of the data transmission device is continuously cut off during inspection and repair, this is determined to be a failure, and the output signal is forcibly cut off. Therefore, the optimum value is set experimentally. Further, the limit number n ₁ is set to 2 in the embodiment. Note that when n ₁ = 1 is set, the speed of detecting an anomaly is increased, but the signal-less signal resulting from the normal signal-less duration during the construction of the information ring described above is detected as a signal-less signal due to a failure, There is a concern that the output signal will be forcibly cut off. Therefore, n ₁ = 2 is set so that the output signal is forcibly cut off only when an actual failure occurs.

Next, a period (T _B + R) in which the random number R output from the random number generation circuit 27 is added to the filter circuit 25 for a predetermined time T _B longer than the predetermined time T _A for the filter circuit 24,
And the lower limit number n ₂ is applied as a parameter. Then, when the signal-less signal is input only the lower limit number n ₂ or less when the period (T _B + R) has elapsed, the filter circuit 25 resets the reset terminal R of the next flip-flop 26 to the H level. Apply a signal. Therefore, the output terminal Q of the flip-flop 26 is converted to the L level, the open signal of the H level is released, and the close signal of the L level is transmitted. When the L level closing signal is sent from the transmission prohibition control circuit 23, the switch circuits 21a and 21b are closed. Therefore, the transmission signal output from the MAC layer 5 is normally transmitted to each bus line 1a, 1b.

The lower limit number n ₂ is the same value as the limit number n ₁ 2
Is set to Further, the value of the random number R output from the random number generation circuit 27 is a value that is always different in all stations 2 from the terminal numbers 1 to N, and for a predetermined time T _B
It is a value such that it becomes a minute time compared to.

In the duplex bus type data transmission device configured as described above, each station 2 normally operates on each bus line 1
If access to a and 1b is possible, an information ring is formed between each station 2 and when the token is normally circulating, in each station 2, there is no signal continuation exceeding the above-mentioned specified time Tm. Since the time is not counted, each switch circuit 21a, 21b maintains the closed state.

Then, when some abnormality occurs and the signal line to the bus line 1a of the station ST _X is disconnected as shown in FIG. 5, or noise is mixed in one of the bus lines 1a and 1b, When many errors occur in the received signal, the bus line selection circuit 10 operates to continue data transmission using a normal bus line.

Next, as shown in FIG. 6, each station ST _X , ST _Y
When the signal lines for the bus lines 1a and 1b different from each other are disconnected in the station ST, as shown in FIG.
_When the data D _X having a length exceeding the specified time Tm is transmitted in the state where _X captures the token, the no-signal state detection circuit 22 of the station ST _Y operates to send a pulse-like signal to the transmission prohibition control circuit 23. No signal is sent. Therefore, the filter circuit 24 registers the first signal-less signal.

At this point, as described above, if there is no signal duration longer than the specified time Tm when the information ring is constructed in the normal state and the first no-signal signal is already registered in the filter circuit 24, it is immediately The flip-flop 26 is set, and the switch circuits 21a and 21b are released.

The switch circuits 21a and 21b are not opened only by registering the first signal-less signal in the filter circuit 24.

On the other hand, when the no-signal duration exceeds the specified time Tm,
The token bus system control program stored in the NAC layer 5 is activated, and as described above, each bus line 1a, via the switch circuit 21a, 21b that still maintains the token request signal in the closed state. Send to 1b. In addition, since the signal line for the bus line 1b is actually disconnected, it is sent only to the normal bus line 1a. Then, as described above, when the token cannot be captured within the predetermined time, the station ST _Y itself transmits the token and the above-mentioned information ring is transmitted between the stations 2 connected to the bus lines 1a and 1b. Rebuild.

However, even in the reconstructed information ring, the cause of the failure has not been resolved, so the token is
_When the station ST _X captures the data and the station ST _X sends out the data, the station ST _Y again detects that the no-signal duration exceeds the specified time Tm, and the transmission prohibition control circuit 23
The second signalless signal is input to. Therefore, the set signal is sent from the filter circuit 24, the flip-flop 26 is set, and the switch circuits 21a and 21b are opened.

When the switch circuits 21a and 21b are opened, even if the token request signal or the token for reconstructing the control ring is output from the MAC layer 5, these signals are transmitted on the bus lines 1a and 1b. There is no such thing. Therefore, the station ST _Y is regarded as not capturing the token, and the token circulates among the other stations 2 including the station ST _X , and the data transmission is normally continued.

The station ST _Y receives the data D from each station 2 except the station ST _X which is sent to each bus line 1a, 1b even if each switch circuit 21a, 21b is opened. Therefore, the station ST _Y is in a standby state waiting for failure recovery.

Then, when the disconnection failure of one of the stations ST _X , ST _Y is recovered, data transmission becomes possible using the normal bus line 1a, 1b, so the station ST _Y
It becomes possible to detect the data D _X of the station ST _X transmitted on one of the bus lines 1a and 1b. Therefore, the no-signal state detection circuit 44 stops transmitting the no-signal signal. When the suspension period reaches the period (T _B + R) described above, the filter circuit 25 in the transmission prohibition control circuit 23 operates and sends a reset signal to the flip-flop 26. Therefore, the flip-flop 23 is reset and the switch circuits 21a and 21b are closed. Therefore, when this station ST _Y captures the token, its data D _Y
Can be sent to the bus lines 1a and 1b.

Therefore, this dual bus type data transmission device can continue data transmission between all stations 2 including the restored station ST _Y.

Next, the filter circuit 25 of the transmission prohibition control circuit 23 uses the random number R
The effect of setting the period (T _B + R) obtained by adding will be described.

In the sixth figure, since the station ST _X, the ST _Y is equal to each other, the station ST when _Y also transmits data D _Y exceeding station ST _X as well as the specified time Tm, the no-signal state detection circuit in the station ST _X Also sends a no signal signal. In such a case, both failed stations ST
_X and ST _Y may be in the standby state at the same time. When both stations ST _X and ST _Y simultaneously shift to the standby state, both stations ST _X and ST _Y no longer detect the no-signal duration. Therefore, both stations ST _X and ST _Y are released from the standby state at the same time even though the failure recovery is not actually performed. Then, again, a signalless duration caused by both stations ST _X , ST _Y occurs. Therefore, both stations ST _X and ST _Y are simultaneously moved to the standby state again. In this way, the standby state and the standby recovery state are repeated indefinitely. Therefore, in the data transmission device, the abnormal state is not permanently released.

In order to eliminate such an inconvenience, by incorporating the term of the random number R into the period (T _B + R) applied to the filter circuit 25 that defines the time from the standby state transition time to the standby state recovery time, each station ST By delaying the time to recover from the standby state between _X and ST _Y , one of the stations intentionally recovers from the standby state earlier and the other station, which is still in the standby state, detects the no signal duration. Therefore, the other station can be made to continue the standby state. Therefore, this data transmission device can maintain the state in which only one of the stations is in the standby state, and the data transmission can be normally continued between the stations except the station in the standby state.

In this way, even if a plurality of stations become unable to access different bus lines, only the station that cannot access one bus line is forced to enter the standby state. As a result, data transmission can be continued, damage can be suppressed to a minimum, and system down of the entire device can be prevented.

The present invention is not limited to the above embodiment. In the apparatus of the embodiment, the no-signal state detection circuit for measuring the no-signal duration is independently provided outside the MAC layer 5, but the token incorporated in the program for controlling the token bus system in the MAC layer 5 It may be common with the timer circuit for setting the timing of transmitting the request signal. Further, the token request signal may be regarded as a signal-less signal and applied to the transmission prohibition control circuit 23.

Furthermore, by adding a weighting considering the degree of importance to each station 2 to the random number R, the more important station among the stations that have transited to the standby state at the same time recovers from the standby state first, and is not so important. It is also possible to keep the station in a waiting state.

[Effects of the Invention] As described above, according to the duplex bus system data transmission apparatus of the present invention, when the no-signal state of the received signal exceeds a predetermined time, signal transmission from the corresponding station to the bus line is forced. It is shut off. Therefore, even if the bus lines different from each other are disconnected between the plurality of stations, the system down of the entire apparatus can be prevented and the damage can be minimized. As a result, the reliability of the entire device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of each station in a dual bus data transmission apparatus of the present invention, FIG.
FIG. 1 is a block diagram showing a transmission prohibition control circuit of the implementation system, FIG. 3 is a block diagram showing a general duplex bus type data transmission device, and FIG. 4 is a block diagram showing a schematic configuration of each station in a conventional device. Figures, 5 and 6
FIG. 7 is a diagram showing a general failure state, and FIG. 7 is a time chart for explaining the problems of the conventional device. 1a, 1b …… bus line, 2, ST _X , ST _Y …… station, 4
...... Changeover switch, 5 ...... MAC layer, 8a, 8b ...... Error detection circuit, 9 ...... First arrival judging circuit, 10 ...... Bus line selection circuit, 21a, 21b ...... Switch circuit, 22 ...... No signal state detection Circuit, 23 ... Transmission inhibition control circuit, 24, 25 ... Filter circuit, 26 ... Flip-flop.

Claims (1)

(57) [Claims] 1. A station is connected to each bus line of two system bus lines for transmitting the same data, and when data transmission using one bus line is disabled, data transmission is performed using the other bus line. In the data transmission device of the duplex bus system, which controls the data transmission timing to each bus line in each station by the token bus system and enables the reconstruction of the information ring by retransmitting the token from each station. The station is provided with a switch circuit which is inserted in a signal transmission path for the two-system bus line and is capable of disconnecting only the signal transmission path, and a no-signal continuation time in the two-system bus line to measure the no-signal duration. A no-signal state detection circuit that outputs a no-signal signal when the duration exceeds a predetermined time, and A transmission prohibition control circuit for transmitting a disconnection release signal of the signal transmission path to the switch circuit when the number of outputs of the no signal signal output from the signal state detection circuit reaches a predetermined limit number of times within a predetermined period. And a signal transmission path of its own is separated from the two-system bus line.