JP3363579B2 - Monitoring device and monitoring system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitoring device and a monitoring system, and is preferably applied to a redundant system, for example.

[0002]

2. Description of the Related Art In recent years, there has been a demand for a system having high reliability against failures. For this reason, recent devices, for example,
It is composed of a double redundant system. For example, electronic exchange systems and information processing systems (eg, processor systems)
In such a case, the double redundant system is used.

For example, in a processor system, when the response signal from each module is checked, the failure of each constituent module is monitored, and the failure processing is performed by an interrupt operation. Was to cause serious problems in the operation of.

For example, as fault processing, for example, IPL
By starting (Initial Program Load), data before the failure is erased, or the process is started from the beginning, so it may take time to restart the process.

Further, for example, a system provided with a 0-system processor and a monitoring device for monitoring both the 1-system processor is normally operated by the 0-system processor and is used when the 0-system processor is in use. If a failure occurs, the operation can be performed using the 1-system processor.

If the monitoring device fails, the 0-system processor and the 1-system processor cannot be monitored, system monitoring cannot be performed, and the system function cannot be fulfilled.

[0007]

From the above-mentioned problems, for example, in a system having a redundant system,
If the system includes a component that is not redundantly configured (single component), the system operation is not stopped even if a failure occurs in this single component,
It is required to provide a mechanism that allows the operation to continue in some way.

[0008]

[Means for Solving the Problems ]
Therefore, the monitoring device according to the first aspect of the present invention includes a plurality of constituent devices.
Redundant processor system with
Communication status between a certain device for single communication and processor
(1) Single processor with monitoring device for monitoring
Can be connected to the same common bus that is connected to the target communication device
However, the processor does not
Access to a processor with a single communication target device
Means for monitoring the reply of the response signal to (2) monitoring
If the method cannot detect the reply of the response signal, unify
An ordinary bus that replaces the communication target device via a common bus
A pseudo response means for returning a pseudo response signal in a cycle,
(3) Storage means for storing the history of response by the pseudo response means
And is provided. In addition, according to the second invention,
The monitoring system is a redundant system with multiple components.
A single communication target device that is a constituent device of the sessa system
In the monitoring system that monitors the communication status with the processor
Each component is (1) Processor and single communication target
Can be connected to the same common bus that the device connects to,
For access to the device for single communication by the processor
Then, the response signal to the processor by the device for single-duplex communication is
The monitoring means for monitoring the reply of the issue and (2) the monitoring means responds
If the signal reply cannot be detected,
Normal bus cycle via common bus instead of storage
And (3) pseudo response means for returning a pseudo response signal.
Storage means for storing the history of the similar response means responding
It is characterized by

[0009]

According to the first aspect of the present invention described above , the monitoring device is
And unification communication target apparatus, and monitors the communication status between the processors, for example, abnormal If you <br/> detect (situation like that does not respond), the monitoring device on behalf of the unification communication target device You can respond. This reduces the risk of stopping the system operation.

[0010] According to a second aspect of the present invention described above, Oh <br/> Ru configuration device, and monitors the communication status between the unification communication target device and the processor, for example, abnormal (response not the situation, etc.) you detect, the configuration device unification communication pairs
It can respond on behalf of the elephant device. This reduces the risk of stopping the system operation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings. "First embodiment": The first embodiment is a case where the present invention is applied to a double redundant type electronic exchange system. FIG. 1 is a block diagram of this double redundant type electronic exchange system. In FIG. 1, the double redundant electronic exchange system is
The central processing unit P1 and the main memory M on the system common bus B1
1, an input / output control device IO1, and a time division exchange switch S
W1 is connected to the 0-system side of the data control device DC1 and the 0-system side of the system monitoring device SK1. An input / output device IO3 is connected to the input / output control device IO1. The input / output device IO3 is a personal computer or the like.

Further, the 1-system common bus B2 has a central processing unit P2, a main memory M2, and an input / output control unit IO2.
, Time division exchange switch SW2, and data control device DC
The 1-system side of 1 and the 1-system side of the system monitoring device SK1 are connected.

The data control device DC1 carries out "transfer of control information (for example, operation data)" between the 0-system side and the 1-system side. This control information is transferred at the stage where processing is performed on the 0-system side in order to continue the operation on the 1-system side instead of the 0-system side when the 0-system side fails. By giving operation data etc. to the 1-system side, when switching from the 0-system side to the 1-system side operation,
This is so that the operation can be continued.

(Data control device DC1):
The data controller 20 of FIG. 1 having a characteristic configuration in this embodiment is connected to a 0-system common bus B1, a monitoring circuit K1, a pseudo-responder G1, a register R1, and a 1-system common bus B2. Monitoring circuit K2 and pseudo-responder G2
, A register R2, and a data controller DC1a connected to the 0-system common bus B1 and the 1-system common bus B2.

((0 system)): In the monitoring circuit K1, the pseudo-responder G1, and the register R1 connected to the 0 system common bus B1 of the data control device DC1, the central processing unit P1 is the system monitoring device. It is to monitor whether or not there is a response when accessing SK1. The monitoring circuit K1 of the data control device DC1 detects whether or not the system monitoring device SK1 returns the response signal a1 in response to the access from the central processing unit P1 to the system monitoring device SK1.

Then, the pseudo-responder G1 outputs the response signal a.
When the monitoring circuit K1 notifies that the 1 has not been returned (detected as a failure), the system monitoring device SK1
Instead of the response signal a1 *. Then, the register R1 stores (sets in the fault bit) as history (fault information) that the pseudo-responder G1 of the data control device DC1 returns the response signal to the central processing unit P1.

((1 system)): The monitoring circuit K2, the pseudo-responder G2, and the register R2 connected to the 1-system common bus B2 of the data control device DC1 are connected to the central processing unit P2. The monitoring device SK1 monitors whether or not a response is made when accessed. The monitoring circuit K2 of the data control device DC1 responds to the access from the central processing unit P2 to the system monitoring device SK1 by the system monitoring device SK1 receiving the response signal a.
It is to detect whether or not 2 is returned.

Then, the pseudo-responder G2 receives the response signal a.
When the monitoring circuit K2 notifies that the 2 has not been returned (a failure has been detected), the system monitoring device SK1
Instead of the response signal a2 *. The register R2 stores (sets in the fault bit) as history (fault information) that the pseudo-responder G2 of the data control device DC1 returns the response signal to the central processing unit P2.

((Data controller DC1a)): Then, the data controller DC1a of the data controller DC1.
Receives the control information from the central processing unit P1.
The control information from the central processing unit P2 is also given to the central processing unit P1.

(System monitoring device SK1): The system monitoring device SK1 of FIG. 1, which is a characteristic configuration of this embodiment, is connected to the 0-system common bus B1.
Monitoring circuit K3, pseudo-responder G3, register R3, monitoring circuit K4 connected to 1-system common bus B2, pseudo-responder G4, register R4, 0-system common bus B1 and 1-system common bus B2 And a control circuit C1 connected to the.

((0 system)): In the monitoring circuit K3, the pseudo-responder G3, and the register R3, which are connected to the 0 system common bus B1 of the system monitoring device SK1, the central processing unit P1 is the data control device. It is to monitor whether or not a response is made when the DC is accessed. The monitoring circuit K3 of the system monitoring device SK1 detects whether or not the data control device DC1 returns the response signal a3 in response to the access from the central processing unit P1 to the data control device DC1.

When the monitoring circuit K3 notifies that the pseudo-responder G3 does not return the response signal a3 (it is detected as a failure), the data control device DC1.
Instead of the response signal a3 *. Then, the register R3 stores, as a history (fault information), that the pseudo-responder G3 of the system monitoring device SK1 has returned a response signal to the central processing unit P1 (set as a fault bit).
To do.

((1 system)): The monitoring circuit K4, the pseudo-responder G4, and the register R4, which are connected to the system 1 common bus B2 of the system monitoring device SK1, are provided by the central processing device P2. It is to monitor whether or not a response is made when the control device DC1 is accessed. Then, the monitoring circuit K4 of the system monitoring device SK1 causes the data control device DC1 to respond to the access from the central processing unit P2 to the data control device DC1.
It is to detect whether or not is returned.

The pseudo responder G4 then outputs the response signal a.
When the supervisory circuit K4 notifies that the 4 has not been returned (detected as a failure), the response signal a4 * is returned instead of the data control device DC1. Then, the register R4 stores, as a history (fault information), that the pseudo-responder G4 of the system monitoring device SK1 has returned a response signal to the central processing unit P2 (set as a fault bit).
To do.

((Control circuit C1)): Then, the control circuit C1 of the system monitoring device SK1 is the 0-system common bus B.
1 connected to the central processing unit P1 and the main memory M
1, the input / output control device IO1, the time division exchange switch S
It monitors whether there is a failure such as W1 and manages the status. Further, the central processing unit P2, the main memory M2, and the input / output control unit IO2 connected to the 1-system common bus B2
In addition, monitoring and status management for the presence / absence of a failure of the time division exchange switch SW2 are performed.

(Input / output device): The 0-system input / output device IO3 is assumed to be capable of outputting fault information in response to an instruction from the system monitoring device SK1 when a 0-system fault occurs. . Similarly, it is assumed that the input / output device IO4 of the 1st system can also output the failure information in response to a command from the system monitoring device SK1 when a failure occurs in the 1st system.

(Time-division exchange switch): The 0-system time-division exchange switch SW1 of FIG. 1 switches the signal from the incoming line so that the signal can be output from the outgoing line under the control of the central processing unit P1. It is a thing. Similarly, the 1-system time-division exchange switch SW2 also switches the signal from the incoming line so that the signal can be output from the outgoing line under the control of the central processing unit P2.

(Operation of the First Embodiment): The operation of the double redundant electronic exchange system of FIG. 1 will be described.

((Operation when Data Controller DC1 is in Failure)): In FIG. 1, when the central processing unit P1 of system 0 accesses the data controller DC1, some cause When the monitoring circuit K3 of the system monitoring device SK1 detects that the response signal a3 has not been returned for this access due to (fault), the system is automatically monitored when this non-return time exceeds a predetermined time (T1). The pseudo-responder G3 of the device SK1 returns the response signal a3 * to the central processing unit P1 on behalf of the data control device DC1.

It should be noted that this predetermined time (T1) is preferably a time such that a system time-out error does not occur.

Then, the central processing unit P1 periodically confirms the information stored (set) in the register R3 of the system monitoring device SK1, and detects the failure of the data control device DC1 as a failure processing (for example, processing by IPL). , Or interrupt operation). by this,
The system does not stop working.

((Operation when system monitoring device SK1 has a failure)): In FIG.
When the central processing unit P2 of the system accesses the system monitoring device SK1, it is confirmed that the response signal a2 is not returned for this access due to some cause (fault), and the monitoring circuit K2 of the data control device DC1. Is detected, if this non-returned time exceeds a predetermined time (T1),
The pseudo-responder G2 of the data control device DC1 automatically returns the response signal a2 * to the central processing unit P2 instead of the system monitoring device SK1.

Then, the central processing unit P2 periodically confirms the information stored (set) in the register R2 of the data control unit DC1, and detects the failure of the system monitoring unit SK1 by the failure processing (for example, processing by IPL). , Or interrupt operation). by this,
The system does not stop working.

(Effects of the first embodiment): According to the double redundant type electronic exchange system of the first embodiment, a failure occurs in the single control device such as the data control device DC1 and the system monitoring device SK1. Even if it is the 0-system central processing unit P1 or 1
It is possible to detect a failure without causing the central processing unit P2 of the system to perform a failure interrupt operation, and to activate the restarting process by the IPL or the like to logically set the failed single device to the 0 system or It can be separated from system 1. Since the system operation is not stopped in this process, the reliability of the electronic exchange system can be greatly improved compared to the conventional one.

Further, since the failure information is stored in the above-mentioned registers R1 to R4, the central processing unit P1 or the central processing unit P2 of the first system can read this information and continue the system operation.

[Second Embodiment]: The second embodiment is a case where the present invention is applied to a double redundant type electronic exchange system. FIG. 2 is a block diagram of this double redundant type electronic exchange system. In FIG. 2, the description of the same components as those of the double redundant type electronic exchange system of the first embodiment will be omitted, and the characteristically different portions will be mainly described.

[Characteristically different from the first embodiment, when the data control device DC2 of the unifying device is determined to be a failure, the data control device DC2 is switched to the 0-system common bus B1.
It is also configured so that it can be electrically disconnected from the 1-system common bus B2. The data control device DC2 can be automatically re-installed even when it is replaced and electrically installed in the system. "Furthermore, what is characteristically different from the first embodiment is that when the system monitoring device SK2 of the unifying device is determined to be a failure, the system monitoring device SK2 is connected to the 0 system common bus B1.
It is also configured so that it can be electrically disconnected from the 1-system common bus B2. Further, even when the system monitoring device SK2 is replaced and electrically incorporated into the system, the electrical system can be automatically re-incorporated. (Isolation circuit): Therefore, in FIG. 2, specifically, in order to realize the above-mentioned configuration, the isolation circuit A1 for system 0 and the isolation circuit A1 for system 1 are provided in ((data control device DC2)). And an isolation circuit A2. The 0-system isolation circuit A1 receives the 0-system common bus B1 in response to an external control signal (eg, a manual signal, eg, logic “1”).
And the 0-system side of the data control device DC2 are electrically disconnected. Further, by giving a logic "0" as the control signal, the electrical connection can be made again.

Further, in order to realize the above configuration, the isolation circuit A2 for the first system of the data control device DC2.
Are electrically disconnected from the 1-system common bus B1 and the 1-system side of the data control device DC2 by a control signal (for example, a manual signal, for example, logic "1") from the outside. . In addition, a logic "0" is used as a control signal
It is also possible to make electrical connection again by giving.

Further, the ((system monitoring device SK2)) is also provided with a 0-system isolation circuit A3 and a 1-system isolation circuit A4, similarly to the data control device DC2. The isolation circuit A3 for the 0 system is connected between the 0 system common bus B1 and the 0 system side of the system monitoring device SK1 by an external control signal (for example, a manual signal, for example, logic "1"). Are designed to be electrically disconnected. Further, by giving a logic "0" as the control signal, the electrical connection can be made again.

Further, in order to realize the above configuration, the isolation circuit A for the first system of the system monitoring device SK2.
4 is a control signal from the outside (for example, a manual signal,
For example, the logical "1") electrically disconnects the 1-system common bus B1 from the 1-system side of the system monitoring device SK2. Further, by giving a logic "0" as the control signal, the electrical connection can be made again.

By providing the isolation circuit as described above in the data control device DC2 and the system monitoring device SK2, the 0-system common bus B1 and the 1-system common bus can be electrically separated without affecting. Furthermore, it is possible to incorporate the system into the system again without stopping the operation of the system.

(Operation of the Second Embodiment): The operation of the double redundant type electronic exchange system of FIG. 2 will be described focusing on the parts different from the first embodiment. If a failure occurs in the data control device DC2 or the system monitoring device SK2, the 0-system central processing unit P1 or the 1-system central processing unit P2 can detect the failure without interrupt operation. Same as the example.

((Operation when the data control device DC2 has a failure)): Therefore, in FIG. 2, when the 0-system central processing device P1 accesses the data control device DC2, something will happen. When the monitoring circuit K7 of the system monitoring device SK2 detects that the response signal a3 has not been returned for this access due to the cause (failure) of the above, if the non-returning time exceeds a predetermined time (T1), it is automatically Pseudo-responder G of system monitor SK2
7 returns a response signal a3 * to the central processing unit P1 in place of the data control device DC2.

Then, the central processing unit P1 periodically confirms the information stored (set) in the register R7 of the system monitoring device SK2, and the failure of the data control device DC2 is dealt with by the failure processing (for example, processing by IPL). , Or interrupt operation). by this,
The system does not stop working.

The fact that the data control device DC2 has a failure is output from the input / output device IO3 through the input / output control device IO1 as failure information, for example, a message. When the maintenance person confirms this message output, a control signal (for example, logic "1") is sent to the isolation circuit A1 in order to electrically disconnect the data control device DC2 from the 0-system common bus B1 and the 1-system common bus B2. Give to A2. This allows the data controller DC2 to be disconnected and replaced without affecting the bus.

Even if this disconnection is carried out, the central processing unit P1 periodically registers with the register R of the system monitoring unit SK2.
Since the information stored (set) in 7 is confirmed,
The system operation can be continued without trouble processing.

Next, when the data controller DC2 is replaced and physically incorporated into the system again, a control signal (for example, logic "0") is sent to the isolation circuits A1, A2.
Give to. As a result, the data control device DC2 is set to 0
The system common bus B1 and the system 1 common bus B2 are electrically connected without affecting.

When an access request is given from the 0-system central processing unit P1 to the data control unit DC2, the response signal a3 is returned. The response signal a3 allows the 0-system central processing unit P1 to access the data control device DC2 normally thereafter without being affected by it.

((Operation when system monitoring device SK2 is in trouble)): In FIG.
When the central processing unit P2 of the system accesses the system monitoring device SK2, the monitoring circuit K6 of the data control device DC2 indicates that the response signal a2 is not returned to this access for some reason (fault). Is detected, if this non-returned time exceeds a predetermined time (T1),
The pseudo-responder G6 of the data control device DC2 automatically returns the response signal a2 * to the central processing unit P2 instead of the system monitoring device SK2.

Then, the central processing unit P2 periodically confirms the information stored (set) in the register R6 of the data control unit DC2, and detects the failure of the system monitoring unit SK2 by the failure processing (for example, the processing by the IPL). , Or interrupt operation). by this,
The system does not stop working.

The fact that the system monitoring device SK2 has a failure is output from the input / output device IO4 through the input / output control device IO2 as failure information, for example, a message. When the maintenance person confirms this message output, a control signal (for example, logic "1") is sent to the isolation circuit A3 to electrically disconnect the system monitoring device SK2 from the 0 system common bus B1 and the 1 system common bus B2. A4
Give to. This allows the system monitoring device SK2 to be disconnected and replaced without affecting the bus.

Even if this disconnection is carried out, the central processing unit P2 will periodically perform the register R6 of the data control unit DC2.
Since the information stored (set) in is confirmed, it is possible to continue the system operation without the failure processing.

Next, when the system monitoring device SK2 is replaced and physically incorporated into the system again, a control signal (for example, logic "0") is sent to the isolation circuit A3.
Give to A4. As a result, the system monitoring device SK2
Are electrically connected without affecting the 0-system common bus B1 and the 1-system common bus B2.

When an access request is given to the system monitor SK2 from the central processing unit P2 of system 1, the response signal a2 is returned. The response signal a2 allows the central processing unit P2 of the first system to normally access the system monitoring unit SK2 without being affected.

(Effect of the Second Embodiment): According to the double redundant type electronic exchange system of the second embodiment described above, a failure occurs in the single control device such as the data control device DC2 and the system monitoring device SK2. Even if it is the 0-system central processing unit P1 or 1
It is possible to detect a failure without causing the central processing unit P2 of the system to perform a failure interrupt operation, and also to give a control signal to the unifying device that causes a failure without activating restart processing by IPL or the like. It can be electrically disconnected without affecting the 0-system bus or the 1-system bus. Since the system operation is not stopped in this process, the reliability of the electronic exchange system can be greatly improved compared to the conventional one.

Furthermore, by giving a control signal to the isolation circuit, the data control device DC2 or the system monitoring device SK2 after replacement can be automatically connected without affecting the bus and the central processing unit P1 or P2, etc. And the exchange of signals can be restarted.

Further, since the failure information is stored in the above-mentioned registers R5 to R8, the central processing unit P1 or the central processing unit P2 of the 1st system can read this information and continue the system operation.

(Other Embodiments) (1) In the above embodiments, a single device between 0 system and 1 system is used.
Data control device DC1 (DC2) and system monitoring device S
Although K1 (SK2) was connected in parallel,
When only the data control device DC1 is connected as one single device, it can be realized by the following configuration. For example, in FIG. 1, the central processing unit P1
When an access signal is given to the data control device DC1 from the data control device DC1, the data control device DC1a is normally made to respond, and if a situation in which the response cannot be made due to a failure or the like occurs, the monitoring circuit K1 is made to monitor. If it is determined that it is not possible, the pseudo-responder G1 may instead be configured to respond to the central processing unit P1 so that the system operation can be continued without causing the fault interrupt processing.

(2) Further, in the above-mentioned embodiment, the application to the electronic exchange system has been described. However, if the time division exchange switches SW1 to SW4 are not provided in the configuration of FIGS. It can also be applied as a redundant information processing system.

(3) Furthermore, by providing the 0-system and 1-system transmission devices, it is possible to realize a dual redundant transmission system.

(4) Furthermore, the present invention is not only applied to a redundant system, but communication between a certain communication device A and another communication device B that is communicating with a communication target that is not redundantly configured. When the situation is monitored and the communication device B cannot respond, the device A monitoring this instead.
Can also be applied when responding instead. Also in this case, the device A can prevent the system operation from being stopped by returning a pseudo response to the communication target, and the reliability can be improved.

Furthermore, by providing the above-mentioned plurality of communication devices with the above-mentioned monitoring function and response function, and monitoring and responding to each other, the reliability of the system can be greatly improved.

[0063]

As described above, according to the monitoring device of the present invention, a plurality of
A redundant processor system that includes the
Between the device that is the target of simplex communication and the processor
In the monitoring device that monitors the communication status of (1)
The same common bus that connects the server and the device for simplex communication
, Which can be connected to the
For the access to the device, it depends on the device for single communication
A monitoring means for monitoring the reply of the response signal to the processor,
(2) When the monitoring means cannot detect the reply of the response signal.
If a single communication target device is used, a common bus is used instead.
A pseudo response that returns a pseudo response signal in a normal bus cycle.
Stores the response means and (3) the history of responses by the pseudo response means.
Since it is provided with the storage means, the single communication target device does not stop its operation and can continue some operation. Therefore, the reliability can be improved.

According to the monitoring system of the present invention,
Structure of redundant processor system with multiple components
Communication between the processor and the target device for simplex communication
In the monitoring system that monitors the situation, each component device
(1) The processor and the device to be unified communication are connected
Can be connected to one common bus and
For access to the target device for duplex communication,
Monitor the response signal sent back to the processor by the device
The monitoring means and (2) the monitoring means can detect the reply of the response signal.
If it does not work, instead of the device for single communication, common
The pseudo response signal is returned in the normal bus cycle through the bus.
The pseudo-response means to be trusted and (3) the pseudo-response means responded.
Since the storage means for storing the history is provided, it is possible to continue some operation without stopping the system operation. Therefore, the reliability of the system can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a double redundant type electronic exchange system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a double redundant type electronic exchange system according to a second embodiment of the present invention.

[Explanation of symbols]

B1 ... 0 system common bus, B2 ... 1 system common bus, DC1 ... Data control device, G1 to G4 ... Pseudo-responder, IO1, IO
2 ... Input / output control device, K1 to K4 ... Monitoring circuit, M1, M
2 ... Main storage device, P1, P2 ... Central processing unit, R1-R
4 ... Register, SK1 ... System monitoring device, SW1, S
W2 ... Time division exchange switch.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04Q 11/04 G06F 11/16 310 G06F 11/30 G06F 13/00 351 H04L 12/24 H04L 29/14 H04M 3/22 H04Q 3/545

Claims (3)

(57) [Claims] 1. A redundant system processor having a plurality of constituent devices.
In the system, the target device for simplex communication that is the relevant device
The monitoring device that monitors the communication status between the
And the processor and the above-mentioned device for single communication connection are the same
Can be connected to the common bus of
Single access to the communication target device
Supervises the reply of the response signal to the processor by the communication target device
The monitoring means to be viewed and the monitoring means could not detect the reply of the response signal.
In this case, instead of the device for single communication, the common
A pseudo response signal is returned in a normal bus cycle through the bus
And a storage means for storing a history of the response made by the pseudo response means.
A monitoring device comprising: 2. A redundant system processor having a plurality of constituent devices.
Systems that are the constituent devices of the system
In a monitoring system for monitoring the communication status with a sessa, each of the above-mentioned constituent devices is the same as the processor and the above-mentioned device for single communication connection.
Can be connected to the common bus of
Single access to the communication target device
Supervises the reply of the response signal to the processor by the communication target device
The monitoring means to be viewed and the monitoring means could not detect the reply of the response signal.
In this case, instead of the device for single communication, the common
A pseudo response signal is returned in a normal bus cycle through the bus
And a storage means for storing a history of the response made by the pseudo response means.
A monitoring system comprising: 3. The device for single communication is an external device.
If it is determined to be more trouble,
Electrical isolation from the common bus based on control signals
In addition, after detecting the replacement of the self-duplex communication target device,
Serial common bus and automatically separating and resumption means that the electrical Resume
The monitoring system according to claim 2, further comprising:
Mu.