JP7635746B2 - Diagnostic circuit and duplicated control circuit - Google Patents

Description

This disclosure relates to a diagnostic circuit and a dual control circuit.

Conventionally, devices are known that detect sticking faults in which the signal level of a transmission signal is stuck at one of two values (see, for example, Patent Document 1).

JP 2017-102569 A

Improvements to the reliability of data input/output modules are required.

The present disclosure has been made in consideration of the above points, and aims to provide a diagnostic circuit and a redundant control circuit that can improve the reliability of data input/output modules.

A diagnostic circuit according to some embodiments includes a pulse generating unit that generates a pulse signal to be superimposed on a signal line that propagates a control signal, a pulse detecting unit that detects the pulse signal from the signal line, and a diagnostic unit that outputs information indicating that the state of the signal line is abnormal if the pulse detecting unit cannot detect the pulse signal. When the signal level of the control signal is HI, the pulse generating unit generates a signal that changes the signal level of the control signal to LO for a predetermined time as the pulse signal, and when the signal level of the control signal is LO, generates a signal that changes the signal level of the control signal to HI for a predetermined time as the pulse signal. This makes it easier to detect a sticking fault. As a result, the reliability of the input/output module is improved.

In one embodiment of the diagnostic circuit, the signal lines may include a system signal line and a field signal line that are insulated from each other by an isolation circuit. The pulse generating unit may superimpose the pulse signal on the system signal line. The pulse detecting unit may detect the pulse signal from the field signal line. In this way, it becomes easier to detect a sticking fault even in a module that includes two isolated circuits. As a result, the reliability of the input/output module is improved.

In one embodiment of the diagnostic circuit, the pulse generating unit may output the timing at which the pulse signal was generated to the pulse detecting unit. The pulse detecting unit may detect the pulse signal by reading the signal propagating through the signal line at the timing obtained from the pulse generating unit. In this way, the pulse signal becomes easier to detect. As a result, diagnostic accuracy is improved.

The diagnostic circuit according to one embodiment may further include a latch circuit that holds a signal level changed by the pulse signal. The pulse detection unit may detect that the pulse signal has been superimposed on the signal line based on the signal level held by the latch circuit. In this way, the pulse signal becomes easier to detect. As a result, diagnostic accuracy is improved.

The duplex control circuit according to some embodiments includes a state control circuit that controls the state of each of the first and second modules. The first and second modules each include the diagnostic circuit and a switch connected to an input/output terminal of the diagnostic circuit. The state control circuit outputs a control signal that controls the open/close state of the switch so that the open/close state of the switch of the first module and the open/close state of the switch of the second module are opposite to each other. In this way, a failure of one of the duplicated modules is less likely to be overlooked. As a result, the reliability of the duplex control module is improved.

The diagnostic circuit and duplex control circuit disclosed herein can improve the reliability of data input/output modules.

FIG. 1 is a block diagram showing an input/output module according to a comparative example. FIG. 2 is a block diagram showing a configuration example of an input/output module according to an embodiment. 11 is a graph showing an example of the waveform of a signal in which a pulse is superimposed on a control signal representing LO. 11 is a graph showing an example of the waveform of a signal in which a pulse is superimposed on a control signal representing a HI level. FIG. 2 is a block diagram showing a configuration example of a duplicated input/output module. FIG. 2 is a block diagram showing a configuration example of an input/output module including an isolation circuit.

Comparative Example
1, an input/output module 900 according to the comparative example includes an input/output control circuit 910, a state control circuit 920, a switch 930, a signal line 950, and a diagnostic line 940. The input/output module 900 is connected to a field device 960 at one end of the switch 930. The input/output module 900 inputs and outputs data between the field device 960 and the input/output module 900 when in an operating state.

The state control circuit 920 controls whether the state of the input/output module 900 is in an operating state or a stopped state. The state control circuit 920 outputs a HI control signal to the signal line 950 when the input/output module 900 is in an operating state, and outputs a LO control signal to the signal line 950 when the input/output module 900 is in a stopped state. The switch 930 is in a closed state when the input/output module 900 is in an operating state, and provides electrical continuity between the input/output control circuit 910 and the field device 960. The switch 930 is in an open state when the input/output module 900 is in a stopped state, and cuts off electrical continuity between the input/output control circuit 910 and the field device 960. The input/output module 900 controls the connection with the field device 960 by controlling the open/close state of the switch 930, and connects to the field device 960 when in an operating state.

The input/output control circuit 910 acquires a control signal from the diagnostic line 940 and diagnoses whether the state of the input/output module 900 recognized by the input/output control circuit 910 itself matches the control signal. If the input/output control circuit 910 acquires a LO control signal from the diagnostic line 940 even though the input/output module 900 is in an operating state, or if the input/output control circuit 910 acquires a HI control signal from the diagnostic line 940 even though the input/output module 900 is in a stopped state, it determines that the control signal is abnormal.

However, regardless of whether the state control circuit 920 outputs a HI or LO control signal, an abnormality in the signal line 950 may cause the signal that the input/output control circuit 910 obtains from the diagnostic line 940 to be stuck at either HI or LO. If a sticking fault occurs and the control signal output by the state control circuit 920 happens to match the stuck state, the input/output control circuit 910 cannot detect the sticking fault.

As described above, the input/output control circuit 910 according to the comparative example may not be able to detect a stuck fault in the signal line 950. This reduces the reliability of the input/output module 900 according to the comparative example.

Therefore, this disclosure describes a diagnostic circuit that can improve the reliability of the data input/output module 100 (see Figure 2).

(Embodiment)
As shown in FIG. 2, the input/output module 100 according to an embodiment of the present disclosure includes an input/output control circuit 110, a state control circuit 120, and a switch 130. The input/output control circuit 110 is connected to a field device 800 via the switch 130. The input/output control circuit 110 includes an input/output terminal for inputting/outputting with the field device 800. The switch 130 is connected to an input/output terminal of the input/output control circuit 110 at one end and to the field device 800 at the other end. The switch 130 transitions to either a closed state in which the terminals are conductive, or an open state in which the terminals are insulated. When the input/output module 100 is in an operating state, the switch 130 is closed to connect the field device 800 and the input/output control circuit 110 to conduction, and data is input/output between the field device 800 and the input/output control circuit 110. When the input/output module 100 is in a stopped state, the switch 130 is opened to disconnect the field device 800 from the input/output control circuit 110.

The state control circuit 120 outputs a HI control signal to close the switch 130 when the input/output module 100 is in an operating state, and outputs a LO control signal to open the switch 130 when the input/output module 100 is in a stopped state. The HI control signal and the LO control signal may be distinguished by voltage or by current. In this embodiment, the LO control signal is a voltage signal close to the ground voltage. The HI control signal is a voltage signal close to the power supply voltage. The state control circuit 120 and the switch 130 are connected by a signal line 150. The control signal propagates through the signal line 150.

In the input/output module 100, the state control circuit 120 outputs a control signal whose level (HI or LO) corresponds to the state of the input/output module 100. However, in the input/output module 100, an output failure may occur in which the level of the control signal output by the state control circuit 120 differs from the level corresponding to the state of the input/output module 100. Furthermore, regardless of the level of the control signal output by the state control circuit 120, a fixation failure may occur in which the level of the control signal propagating through the signal line 150 is fixed to either HI or LO due to an abnormality in the signal line 150.

In the input/output module 100, the input/output control circuit 110 is configured to detect output failures and sticking failures. The input/output control circuit 110 includes a diagnostic unit 116. The diagnostic unit 116 knows whether the input/output module 100 is in an operating state or a stopped state. The diagnostic unit 116 acquires the level of the control signal propagating through the signal line 150 via the diagnostic line 140 in order to confirm whether the state of the input/output module 100 matches the state corresponding to the level of the control signal output from the state control circuit 120. The diagnostic line 140 branches off from the signal line 150 at a node 142 located on the signal line 150. When the state of the input/output module 100 that the diagnostic unit 116 itself recognizes does not match the state corresponding to the level of the acquired control signal, the diagnostic unit 116 detects that at least an output failure may have occurred. When the diagnostic unit 116 detects that at least an output failure may have occurred, it outputs an abnormal state as a diagnosis result of the state of the input/output module 100.

However, there is a possibility that a stuck fault may not be detected by merely acquiring the level of the control signal. This is because, when a stuck fault occurs, if the state of the input/output module 100 coincides with the state corresponding to the level of the stuck control signal, the diagnostic unit 116 will diagnose it as normal. Therefore, even if the state of the input/output module 100 that the diagnostic unit 116 itself grasps matches the state corresponding to the acquired control signal level, the diagnostic unit 116 will not yet output a normal state as the diagnosis result for the state of the input/output module 100.

In the input/output module 100 according to this embodiment, the input/output control circuit 110 further includes a pulse generating unit 112 and a pulse detecting unit 114. The pulse generating unit 112 generates a pulse signal, outputs the pulse signal from a superimposing line 160, and superimposes the pulse signal on a control signal propagating through the signal line 150. The superimposing line 160 merges with the signal line 150 at a node 162 located on the signal line 150. The pulse detecting unit 114 detects the pulse signal superimposed on the control signal propagating through the signal line 150 via a detection line 170. The detection line 170 branches off from the signal line 150 at a node 172 located on the signal line 150.

When the state control circuit 120 outputs an LO control signal, the pulse generating unit 112 generates a pulse signal and superimposes it on the control signal so that the signal level of the control signal becomes HI for a predetermined period of time. As shown in FIG. 3, a signal in which a pulse signal is superimposed on the LO control signal represented by S1 so that the signal level becomes HI for a predetermined period of time is represented as P1. In FIG. 3, the horizontal axis represents time. The vertical axis represents signal strength (signal level).

When the state control circuit 120 outputs a HI control signal, the pulse generating unit 112 generates a pulse signal and superimposes it on the control signal so that the signal level of the control signal becomes LO for a predetermined period of time. As shown in FIG. 4, a signal in which a pulse signal is superimposed on a HI control signal represented by S2 so that the signal level becomes LO for a predetermined period of time is represented as P2. In FIG. 4, the horizontal axis represents time. The vertical axis represents signal strength (signal level).

The pulse detection unit 114 detects a pulse signal from the signal P1 illustrated in FIG. 3 or the signal P2 illustrated in FIG. 4. The pulse detection unit 114 outputs information indicating that a pulse signal has been detected to the diagnosis unit 116. When the diagnosis unit 116 acquires information indicating that a pulse signal has been detected from the pulse detection unit 114, it determines that a sticking fault has not occurred at least between the node 162 and the node 172 of the signal line 150. When the state corresponding to the control signal acquired from the diagnosis line 140 matches the state of the input/output module 100, the diagnosis unit 116 determines that at least the state control circuit 120 has not generated an output fault. When the diagnosis unit 116 determines that neither a sticking fault nor an output fault has occurred, it diagnoses that the state of the input/output module 100 is normal. In other words, when the diagnosis unit 116 acquires information indicating that a pulse signal has been detected from the pulse detection unit 114 and the state corresponding to the acquired control signal matches the state of the input/output module 100, it diagnoses that the state of the input/output module 100 is normal.

When the pulse detection unit 114 cannot detect a pulse signal, the diagnosis unit 116 diagnoses that a sticking fault has occurred in the signal line 150, causing the state of the signal line 150 to become abnormal. In addition, when the state corresponding to the control signal acquired from the diagnosis line 140 does not match the state of the input/output module 100, the diagnosis unit 116 diagnoses that an output fault has occurred in the state control circuit 120, causing the state of the state control circuit 120 to become abnormal.

The input/output module 100 may be equipped with an output device such as a display or speaker that outputs the diagnosis result of the state of the input/output module 100. The diagnosis unit 116 may output the diagnosis result of the state of the input/output module 100 through the output device and notify the user.

The pulse signal superimposed on the control signal may affect the open/closed state of the switch 130. The signal line 150 may include a filter 180 between the switch 130 and the signal line 150. The filter 180 is configured to remove or attenuate the pulse signal. The filter 180 may be configured, for example, as a low-pass filter. The pulse signal may be generated so that it changes only for a short period of time that does not affect the open/closed state of the switch 130. If the pulse signal does not affect the open/closed state of the switch 130, the filter 180 may not be connected to the signal line 150.

The pulse signal superimposed on the control signal may affect the determination of an output fault in the diagnostic unit 116. The diagnostic line 140 may include a filter 144 between the signal line 150 and the diagnostic unit 116. The filter 144 is configured to remove or attenuate the pulse signal. The filter 144 may be configured, for example, as a low-pass filter. The pulse signal may be generated so that it changes only for a short period of time that does not affect the determination in the diagnostic unit 116. If the pulse signal does not affect the determination in the diagnostic unit 116, the filter 144 may not be connected to the diagnostic line 140.

As described above, the input/output module 100 and input/output control circuit 110 according to this embodiment can increase the possibility of detecting a stuck fault by superimposing a pulse signal on a control signal and detecting the pulse signal from the signal line 150. As a result, the reliability of the input/output module 100 can be improved. The input/output control circuit 110, which is equipped with a diagnostic unit 116 and detects a stuck fault, is also called a diagnostic circuit.

Each component of the input/output control circuit 110 or the state control circuit 120 may be configured to include a processor such as a CPU (Central Processing Unit), or may be configured to include a dedicated circuit.

(Duplex control circuit)
In order to increase the availability of data input/output to/from the field device 800, the input/output module 100 may be duplicated. As shown in Fig. 5, the field device 800 may be connected to each of the first input/output module 200 and the second input/output module 300. The field device 800 can input/output data to/from either the first input/output module 200 or the second input/output module 300. The first input/output module 200 is also simply referred to as the first module. The second input/output module 300 is also simply referred to as the second module.

The first input/output module 200 includes a first input/output control circuit 210, a first state control circuit 220, and a first switch 230. The first input/output control circuit 210 is configured identically or similarly to the input/output control circuit 110. The first state control circuit 220 is configured identically or similarly to the state control circuit 120. The first switch 230 is configured identically or similarly to the switch 130. The first state control circuit 220 outputs a control signal to the first switch 230 through a signal line 250. The first input/output control circuit 210 acquires the level of the control signal propagating through the signal line 250 through a diagnostic line 240. The diagnostic line 240 branches off from the signal line 250 at a node 242. The first input/output control circuit 210 generates a pulse signal and superimposes the pulse signal on the control signal through a superimposition line 260. The superimposition line 260 merges with the signal line 250 at a node 262. The first input/output control circuit 210 detects a pulse signal from the signal line 250 through the detection line 270. The detection line 270 branches off from the signal line 250 at a node 272. The first input/output control circuit 210 operates in the same or similar manner as the input/output control circuit 110, and can determine whether an output failure of the first state control circuit 220 or a sticking failure of the signal line 250 has occurred.

The second input/output module 300 includes a second input/output control circuit 310, a second state control circuit 320, and a second switch 330. The second input/output control circuit 310 is configured identically or similarly to the input/output control circuit 110. The second state control circuit 320 is configured identically or similarly to the state control circuit 120. The second switch 330 is configured identically or similarly to the switch 130. The second state control circuit 320 outputs a control signal to the second switch 330 through a signal line 350. The second input/output control circuit 310 acquires the level of the control signal propagating through the signal line 350 through a diagnostic line 340. The diagnostic line 340 branches off from the signal line 350 at a node 342. The second input/output control circuit 310 generates a pulse signal and superimposes the pulse signal on the control signal through a superimposition line 360. The superimposition line 360 merges with the signal line 350 at a node 362. The second input/output control circuit 310 detects a pulse signal from the signal line 350 through the detection line 370. The detection line 370 branches off from the signal line 350 at a node 372. The second input/output control circuit 310 operates in the same or similar manner as the input/output control circuit 110, and can determine whether an output failure of the second state control circuit 320 or a sticking failure of the signal line 350 has occurred.

The first input/output module 200 and the second input/output module 300 operate to complement each other. Specifically, when the first input/output module 200 is in an operating state, the second input/output module 300 is in a stopped state. Conversely, when the second input/output module 300 is in an operating state, the first input/output module 200 is in a stopped state. The first state control circuit 220 and the second state control circuit 320 arbitrate the states of the first input/output module 200 and the second input/output module 300, respectively, and output a control signal according to the arbitration result. The first state control circuit 220 and the second state control circuit 320 are also collectively referred to as a duplex control circuit. The first input/output module 200 and the second input/output module 300 are also collectively referred to as a duplex control module. As a result of the states being reversed between the first input/output module 200 and the second input/output module 300, the open/close state of the first switch 230 of the first input/output module 200 and the open/close state of the second switch 330 of the second input/output module 300 are reversed to each other.

Even if one of the circuits or modules fails, the duplicated control circuit and duplicated control module can continue inputting and outputting data to and from the field device 800 through the non-failed circuit or module. If a sticking fault is overlooked, the fault may be left unattended when one of the circuits or modules fails. If the other circuit or module fails while the fault is left unattended, data input and output to and from the field device 800 may be cut off. Overlooking a sticking fault may have a significant impact on the reliability of the duplicated control circuit and duplicated control module. The duplicated control circuit and duplicated control module according to this embodiment can increase the possibility of detecting a sticking fault using a pulse signal. As a result, the reliability of the duplicated control circuit and duplicated control module may be improved.

In FIG. 5, a circuit for removing or attenuating a pulse signal, such as a low-pass filter, may be connected to the diagnostic line 240 or 340. Also, a circuit for removing or attenuating a pulse signal, such as a low-pass filter, may be connected to the signal line 250 or 350 between the node 272 or 372 and the first switch 230 or the second switch 330.

(Example of a configuration including two circuits that are insulated from each other)
6, the input/output module 400 is divided into two circuits that are insulated from each other at a boundary represented by a dashed line. The input/output module 400 includes a system control circuit 410 and a state control circuit 420 on one side of the isolation boundary. The input/output module 400 includes a field control circuit 418 and a switch 430 on the other side of the isolation boundary.

The state control circuit 420 outputs a control signal to the switch 430 through signal lines 450 and 452, which are insulated from each other by an isolation circuit 490. The signal line 450 is also called a system signal line. The signal line 452 is also called a field signal line. The isolation circuit 490 insulates the signal lines 450 and 452 from each other, while transmitting the control signal transmitted to the signal line 450 to the signal line 452. The isolation circuit 490 may be configured to include an element that transmits a signal without using an electric wire, such as an isolation coupler that communicates using an optical signal.

The combined configuration of the system control circuit 410 and the field control circuit 418 corresponds to the input/output control circuit 110 (see FIG. 2) in the input/output module 100 when insulation is not included. The system control circuit 410 includes a pulse generating unit 412 and a diagnostic unit 416. The pulse generating unit 412 is configured the same as or similar to the pulse generating unit 112. The diagnostic unit 416 is configured the same as or similar to the diagnostic unit 116. The field control circuit 418 includes a pulse detecting unit 414. The pulse detecting unit 414 is configured the same as or similar to the pulse detecting unit 114.

The diagnostic unit 416 of the system control circuit 410 knows whether the input/output module 400 is in an operating state or a stopped state. The diagnostic unit 416 acquires the level of the control signal propagating through the signal line 450 via the diagnostic line 440 in order to check whether the state of the input/output module 400 matches the state corresponding to the level of the control signal output from the state control circuit 420. The diagnostic line 440 branches off from the signal line 450 at a node 442 located on the signal line 450. If the state of the input/output module 400 that the diagnostic unit 416 itself recognizes does not match the state corresponding to the level of the acquired control signal, the diagnostic unit 416 detects that at least there is a possibility that an output failure has occurred. If the diagnostic unit 416 detects that at least there is a possibility that an output failure has occurred, it outputs an abnormal state as the diagnosis result of the state of the input/output module 400.

The pulse generating unit 412 of the system control circuit 410 generates a pulse signal, outputs the pulse signal from the superimposition line 460, and superimposes the pulse signal on the control signal propagating through the signal line 450. The superimposition line 460 merges with the signal line 450 at a node 462 located on the signal line 450. The control signal on which the pulse signal is superimposed propagates from the signal line 450 to the signal line 452 through the insulation circuit 490. The pulse detection unit 414 of the field control circuit 418 detects the pulse signal superimposed on the control signal propagating through the signal line 452 via the detection line 470. The detection line 470 branches off from the signal line 452 at a node 472 located on the signal line 452.

When the pulse detection unit 414 detects a pulse signal, it outputs information indicating that a pulse signal has been detected to the diagnosis unit 416 via the communication line 492. The communication line 492 indicates communication between the system control circuit 410 and the field control circuit 418. The system control circuit 410 and the field control circuit 418 may communicate wirelessly or wired. When the system control circuit 410 and the field control circuit 418 communicate wired, the communication line 492 may be configured to include an insulating coupler or the like.

When the diagnostic unit 416 acquires information indicating that a pulse signal has been detected from the pulse detection unit 414, it determines that no sticking failure has occurred at least between the node 462 of the signal line 450 and the node 472 of the signal line 452, and in the insulation circuit 490. When the state corresponding to the control signal acquired from the diagnostic line 440 matches the state of the input/output module 400, the diagnostic unit 416 determines that at least the state control circuit 420 has no output failure. When the diagnostic unit 416 determines that neither a sticking failure nor an output failure has occurred, it diagnoses that the state of the input/output module 400 is normal. In other words, when the diagnostic unit 416 acquires information indicating that a pulse signal has been detected from the pulse detection unit 414, and when the state corresponding to the acquired control signal matches the state of the input/output module 400, it diagnoses that the state of the input/output module 400 is normal.

The signal line 452 may include a filter 480 between the switch 430. The diagnostic line 440 may include a filter 444 between the signal line 450 and the diagnostic section 416. The filters 480 and 444 are configured to remove or attenuate the pulse signal. The filters 480 and 444 may be configured the same as or similar to the filters 180 and 144. If the pulse signal does not affect the open/closed state of the switch 430, the filter 480 may not be connected to the signal line 452. If the pulse signal does not affect the judgment in the diagnostic section 416, the filter 444 may not be connected to the diagnostic line 440.

As described above, even if the input/output module 400 is divided into two circuits separated by an insulating section, the possibility of detecting a stuck fault can be increased. As a result, the reliability of the input/output module 400 can be improved.

<Output of pulse signal timing>
The pulse generating section 412 of the system control circuit 410 may generate a pulse signal and output the timing at which the pulse signal is superimposed on the signal line 450 to the pulse detecting section 414 of the field control circuit 418. When the pulse detecting section 414 obtains the timing at which the pulse signal is superimposed, the pulse detecting section 414 may calculate or estimate the timing at which the control signal on which the pulse signal is superimposed propagates from the signal line 450 to the signal line 452, based on the timing obtained from the pulse generating section 412.

The pulse detection unit 414 may read the signal propagating through the signal line 452 via the detection line 470 at the calculated or estimated timing, and detect whether a pulse signal is superimposed on the read signal. When the input/output module 400 is divided into two circuits with an insulating boundary therebetween as illustrated in FIG. 6, it is difficult for the pulse detection unit 414 to grasp the timing at which the pulse signal is generated by the pulse generation unit 412. If the timing at which the pulse signal is superimposed on the control signal is unknown, the pulse detection unit 414 needs to continue to monitor the signal propagating through the signal line 452. The pulse detection unit 414 can easily detect the pulse signal by calculating or estimating the timing at which the pulse signal is superimposed on the control signal. In other words, the circuit of the pulse detection unit 414 can be simplified.

As described above, by knowing in advance the timing at which the pulse signal is superimposed, the pulse signal can be easily detected. In the input/output module 100 illustrated in FIG. 2, the diagnostic unit 116 may be configured to obtain the timing at which the pulse signal is generated from the pulse generating unit 112 and detect the pulse signal at the obtained timing. In this case, the filter 144 is not installed in the diagnostic line 140. Also, the pulse detecting unit 114 is included in the diagnostic unit 116.

<Latch circuit 474>
The input/output module 400 may further include a latch circuit 474 between the node 472 of the detection line 470 and the pulse detection unit 414. When a pulse signal is superimposed on the control signal propagating through the signal line 452, the latch circuit 474 holds a change in the level of the signal.

When the state control circuit 420 outputs a HI control signal, the control signal with the pulse signal superimposed thereon temporarily becomes LO level. The latch circuit 474 holds the LO signal level when the control signal propagating through the signal line 452 temporarily becomes LO. The pulse detection unit 414 acquires the signal level held in the latch circuit 474 at an appropriately set timing. If the signal level held in the latch circuit 474 is LO, the pulse detection unit 414 considers that a pulse signal has been detected, and outputs information indicating that a pulse signal has been detected to the diagnosis unit 416.

When the state control circuit 420 outputs a LO control signal, the control signal superimposed with the pulse signal temporarily becomes a HI level. The latch circuit 474 holds the HI signal level when the control signal propagating through the signal line 452 temporarily becomes HI. The pulse detection unit 414 acquires the signal level held in the latch circuit 474 at an appropriately set timing. If the signal level held in the latch circuit 474 is HI, the pulse detection unit 414 considers that a pulse signal has been detected, and outputs information indicating that a pulse signal has been detected to the diagnosis unit 416.

By the latch circuit 474 holding the signal level, the pulse signal is easier to detect even if the pulse generating unit 412 and the pulse detecting unit 414 are separate circuits. As a result, the accuracy of diagnosis can be improved.

In the input/output module 100 illustrated in FIG. 2, a circuit equivalent to the latch circuit 474 may be disposed on the detection line 170. Also, in the first input/output module 200 or the second input/output module 300 illustrated in FIG. 5, a circuit equivalent to the latch circuit 474 may be disposed on the detection line 270 or 370. In the input/output module 100, the first input/output module 200, or the second input/output module 300, the pulse generating unit 112, 212, or 312 and the pulse detecting unit 114, 214, or 314 are each integrated into one circuit. Even when integrated into one circuit in this way, the pulse detecting unit 114, 214, or 314 may not be able to accurately grasp the timing at which the pulse signal was generated due to signal delays within the circuit. By providing the input/output module 100, the first input/output module 200, or the second input/output module 300 with a circuit equivalent to the latch circuit 474, the pulse signal becomes easier to detect. As a result, the accuracy of diagnosis may be improved.

The above describes an embodiment of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and various modifications are also included within the scope that does not deviate from the spirit of this disclosure.

100 Input/Output module (110: Input/Output control circuit, 112: Pulse generating unit, 114: Pulse detecting unit, 116: Diagnosis unit, 120: State control circuit, 130: Switch, 140: Diagnosis line, 142: Node, 144: Filter, 150: Signal line, 160: Superimposition line, 162: Node, 170: Detection line, 172: Node, 180: Filter)
200 First input/output module (210: First input/output control circuit, 220: First state control circuit, 230: First switch, 240: First diagnostic line, 242: Node, 250: First signal line, 260: First overlapping line, 262: Node, 270: First detection line, 272: Node)
300 Second input/output module (310: second input/output control circuit, 320: second state control circuit, 330: second switch, 340: second diagnostic line, 342: node, 350: second signal line, 360: second overlap line, 362: node, 370: second detection line, 372: node)
400 Input/Output module (410: system control circuit, 412: pulse generation unit, 414: pulse detection unit, 416: diagnosis unit, 418: field control circuit, 420: state control circuit, 430: switch, 440: diagnosis line, 442: node, 444: filter, 450: signal line, 460: superposition line, 462: node, 470: detection line, 472: node, 474: latch circuit, 480: filter, 492: communication line)
800 Field Devices

Claims (5)

a pulse generating unit that generates a pulse signal to be superimposed on a signal line that propagates a control signal;
a pulse detection unit that detects the pulse signal from the signal line;
a diagnostic unit that outputs a signal indicating that a state of the signal line is abnormal when the pulse detection unit cannot detect the pulse signal,
The pulse generating unit includes:
generating, as the pulse signal, a signal that changes the signal level of the control signal to LO for a predetermined time when the signal level of the control signal is HI;
generating, as the pulse signal, a signal that changes the signal level of the control signal to HI for a predetermined period of time when the signal level of the control signal is LO;
Diagnostic circuitry. the signal lines include a system signal line and a field signal line that are insulated from each other by an isolation circuit;
the pulse generating unit superimposes the pulse signal on the system signal line;
The pulse detection unit detects the pulse signal from the field signal line.
2. The diagnostic circuit of claim 1. the pulse generating unit outputs a timing at which the pulse signal was generated to the pulse detecting unit;
The diagnostic circuit according to claim 2 , wherein the pulse detection section detects the pulse signal by reading a signal propagating through the signal line at a timing obtained from the pulse generation section. a latch circuit for holding a signal level changed by the pulse signal;
3. The diagnostic circuit according to claim 1, wherein the pulse detection section detects that the pulse signal is superimposed on the signal line based on a signal level held in the latch circuit. A dual control circuit including a state control circuit for controlling a state of each of a first module and a second module,
each of the first module and the second module includes a diagnostic circuit according to any one of claims 1 to 4, and a switch connected between an input/output terminal of the diagnostic circuit and a field device , the switch transitioning between a closed state that connects the input/output terminal of the diagnostic circuit and the field device, and an open state that insulates the input/output terminal of the diagnostic circuit from the field device;
the state control circuit outputs a control signal for controlling the open/closed state of the switch of the first module and the open/closed state of the switch of the second module so that the open/closed state of the switch of the first module and the open/closed state of the switch of the second module are opposite to each other.
Dual control circuit.

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