JPH04320540A - Duplex system - Google Patents

Abstract

PURPOSE:To stabilize the operation of a system consisting of an operating system and a stand-by system by preventing the application of a bus utilization permission to the stand-by system when the stand-by system is abnormally driven even if the stand-by system outputs a bus utilization request. CONSTITUTION:A switching circuit 3 imparts the utilization right of a system bus 4 to an A system CPU 1 or a B system CPU 2. When the CPU 1 is an operating system and the CPU 2 is stand-by system, the CPU 1 uses the bus 4. In the case of switching the CPU 1 to the stand-by system and the CPU 2 to the operating system, the CPU 1 outputs a bus aborting signal 200 to the circuit 3. The circuit 3 judges whether the CPU 2 is normal or not by checking a status signal 300 outputted from the CPU 2, and only when the CPU 2 is normal, outputs a bus utilization permission signal 400 and stops the output of the signal 400 to the CPU 1. When the CPU 2 is abnormal, the circuit 3 does not impart the signal 400 to the CPU 2.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in which bus masters such as CPUs are duplicated, and more particularly to a system for switching between an active system and a standby system.

0002

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional duplex system of this type. Currently, both A-type and B-type CP
When U1 and U2 are not operating, when the A-system CPU 1 outputs the bus request signal 100 to the arbitration circuit 3, the arbitration circuit 3 receives the request signal and outputs the bus use permission signal 101.
is given to CPU1. Thereby, the CPU 1 uses the system bus 4 to execute the job. On the other hand, B-type CP
U2 becomes a standby system. Suppose that the CPU 2 in the standby system goes out of control for some reason and outputs the bus request signal 100 to the arbitration circuit 3 even though the CPU 1 in the A system is in the active system. Since the arbitration circuit 3 performs the process of granting the bus use right in the order of receiving the bus request signal first, when the bus request signal is issued from the CPU 2 as described above, the bus use permission signal 101 is given to the CPU 2. As a result, CPU2, which was originally supposed to be a standby system, started operating using system bus 4, breaking the principle of the redundant system, that is, the principle that the standby system should not destroy the operation of the active system. This has the disadvantage of causing confusion in system processing.

0003

[Problem to be solved by the invention] The conventional two methods as described above
In a redundant system, when a standby system sends a bus request signal to an arbitration circuit due to some kind of failure in response to an active system, this arbitration circuit grants the right to use the bus to the standby system that issued the bus request signal. This had the disadvantage that the standby system could go out of control and cause system failure, and the advantages of the redundant configuration could not be fully utilized.

Therefore, the present invention aims to eliminate the above-mentioned drawbacks, and prevents the standby system from being granted permission to use the bus if the standby system is operating abnormally even if the standby system issues a request to use the bus. The purpose of this invention is to provide a duplex system that can operate stably. [Structure of the invention]

[0005]

[Means for Solving the Problems] The present invention has a plurality of bus masters, and provides redundant control for giving the right to use the bus to one of these bus masters, while not giving the right to use the bus to a standby bus master. In the system, there is a first determining means for determining whether the system that issued the bus relinquishment signal is in a normal state or an abnormal state, and the first determining means determines that the system that issued the bus relinquishment signal is not normal. If it is determined that this is the case, a first bus right switching means performs control such that the bus right abandonment signal is not accepted; a determining means; and a second bus right switching means for performing control such that if the second determining means determines that the system to which the right to use the bus is to be given is in an abnormal state, the right to use the bus is not granted to the system. It has a complete configuration.

[0006]

In the duplex system of the present invention, the first determining means determines whether the system that issued the bus relinquishment signal is in a normal state or in an abnormal state. The first bus right switching means performs control such that the bus right relinquishing signal is not accepted when the first determining means determines that the system that issued the bus right relinquishing signal is not normal. The second determining means determines whether the system to which the right to use the bus is granted is in a normal state or in an abnormal state. The second bus right switching means is configured to perform control such that the bus right is not granted to the system when it is determined by the second determining means that one of the systems to which the right to use the bus is granted is in an abnormal state. It has a configuration.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the duplex system of the present invention. 1 is the CPU of the A system, 2 is the CPU of the B system, 3 is a switching circuit that gives the right to use the system bus 4 to the CPU of the A system or the B system, and 4 is used by the CPU 1 of the A system or the CPU 2 of the B system. It is a system bus.

Next, the operation of this embodiment will be explained. Now, if the A-system CPU 1 is the active system and the B-system CPU 2 is the standby system, the A-system CPU 1 is using the system bus 4 to perform various jobs. After that, the A-based CPU
When the CPU 1 of the A system is to be switched to the standby system and the CPU 2 of the B system to be the active system, the CPU 1 of the A system outputs a bus abandonment signal 200 to the switching circuit 3. When the switching circuit 3 receives the bus abandonment signal 200, it looks at the status signal 300 output from the B-system CPU 2, determines whether the B-system CPU 2 is normal or abnormal, and switches the B-system CPU 2 is normal, the bus use permission signal 400 is sent to this CPU2.
At the same time, the output of the bus use permission signal 400 sent to the A-system CPU 1 is stopped. As a result, the B-system CPU 2 starts processing the job using the system bus 4, while the A-system CPU 1 becomes a standby system.

By the way, when switching between the active system and the standby system as described above, if the switching circuit 3 checks the status signal 300 of the CPU 2 of the B system and finds that the CPU 2 is abnormal, the switching circuit 3 switches the status signal from the CPU 1 of the A system. Regardless of the output of the bus abandonment signal 200, the bus use permission signal 400 is output as is to the CPU 1 of the A system, and the CPU 1 of the A system remains in the active system. At the same time, the switching circuit 3 does not give the bus use permission signal 400 to the B-system CPU 2, keeps it in a standby state, and does not switch between the active system and the standby system.

[0010] Next, when the A-system CPU 1 in operation becomes abnormal, the switching circuit 3 learns of the abnormality of the CPU 1 from the status signal 300 output from the CPU 1. As a result, the switching circuit 3 stops outputting the bus use permission signal 400 that was being sent to the A-system CPU 1, and instead outputs the bus use permission signal 400 to the B-system CPU 2.
is switched to the active system, and the CPU 1 of the A system is switched to the standby system.

Here, even if the B system CPU 2 in the standby state goes out of control and sends the bus abandonment signal 200 to the switching circuit 3,
The switching circuit 3 recognizes that the CPU 2 is abnormal from the status signal output from the B-system CPU 2, and
Since the bus abandonment signal sent from U2 is not accepted, the B-system CPU2 remains in the standby system.

According to this embodiment, the normal/abnormal state of the active system and the standby system is monitored, and if the system that has issued the bus abandonment signal is abnormal, this bus abandonment signal is not accepted, and the bus is not used. If the system that gives the permission signal is abnormal, the bus usage permission signal is not given to this system, which prevents malfunctions such as the standby system going out of control and giving the bus right to the standby system. This makes it possible to maximize the inherent benefits of a redundant system.

[0013]

As described above, according to the redundant system of the present invention, even if the standby system issues a bus use request, if the standby system is operating abnormally, the standby system is granted permission to use the bus. It is possible to perform stable operation by preventing damage from occurring. In the above embodiment, an example in which the present invention is applied to a duplex system has been described, but similar effects can be obtained when the present invention is applied to an n-duplex system. However, n≧2

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a duplex system of the present invention.

FIG. 2 is a diagram showing an example of a conventional duplex system.

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: In a duplex system having a plurality of bus masters, in which one of these bus masters is given the right to use the bus, and a standby bus master is not given the right to use the bus, a bus right relinquishing signal is provided. a first determining means for determining whether the system that issued the bus right relinquishing signal is in a normal state or an abnormal state; a first bus right switching means that performs control not to accept a bus right abandonment signal; a second determining means that determines whether the system to which the right to use the bus is to be given is in a normal state or in an abnormal state; and a second bus right switching means that performs control such that if the system to which the right to use the bus is to be given is determined to be in an abnormal state by the determining means, the right to use the bus is not granted to the system. Duplex system.