JPS62254201A - Malfunction preventing circuit - Google Patents

Abstract

PURPOSE:To prevent the influence caused by a malfunction of another package set on the same bus by increasing forcibly the output signal of a working system up to a level close to the power supply voltage as long as the malfunction of a stand-by system may possibly give an adverse influence to the working system. CONSTITUTION:At the time of a normal operation, a circuit set at the side of a CPU 100 is used and the LOCK signals of both CPU 100 and 200 are kept at low levels. The STB signal of the CPU 200 is set at a low level. Then the LOCK signal of the CPU 200 is set at a high level in case the CPU 100 is defective and replaced. Thus a transistor 203 is turned on and the STB signal is raised up to a level VCC. Therefore the level VCC is kept on a bus even in case the STB signal output is set at a low level while the CPU 100 is replaced. Thus the receiver side is never affected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit system that prevents the operation of a control system from being disturbed due to a malfunction in a timing system when duplication is performed in a process control device or the like.

[Conventional technology]

Conventionally, in order to prevent signal disturbances on the BUS when a package is inserted or removed while the power is on, measures have been taken to prevent unnecessary signals from being output to the package being inserted or removed. Wear manual ) (-7
600 type process input/output crab unit (manufactured by Hitachi).

(Problems to be Solved by the Invention) However, the conventional methods were completely ineffective against malfunctions caused by 0N10FF of the power supply during insertion and removal, malfunctions caused by sparks at the plug, etc.

When a two-piece system is assembled, the system in which the defect occurs is considered the temporary system, and the defective part is replaced. At this time, the power supply for the time system is normally cut off. The logic circuit is uncertain when the power is turned off and turned on. Therefore, during this time, it is necessary to ensure that the execution system is not adversely affected.

An object of the present invention is to provide a malfunction prevention circuit that can completely eliminate the influence of malfunctions of other packages on the same BUS.

[Means for solving problems]

The present invention is applicable to the execution system when the timing system malfunctions.

While there is a risk of adverse effects, the output signal of the execution system is forcibly pulled up to near the power supply voltage, so that even if the timing system outputs a signal, it will be invalidated.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a block diagram of this circuit, and FIG. 2 is an embodiment of this circuit. Furthermore, FIG. 3 is an example of a dual system in which this circuit exhibits its effects.

Before explaining the embodiments, the background why this circuit is necessary will be described.

In process control systems, stopping control immediately leads to a drop in production efficiency, so efforts have been made to improve the reliability of control systems. A redundant system is widely used as one of the methods. FIG. 4, FIG. 5, and FIG. 6 are all examples of duplication.

Figure 4 shows a system in which the entire control system is completely redundant, which is expensive and is therefore used when reliability is particularly required (of course, there are also examples of triplex and quadruplex systems, but the essential There is no significant difference, so we omit it).

Both FIG. 5 and FIG. 6 are examples of partial duplication. In practice, compared to the complete duplexing shown in FIG. 4, there is not much difference in reliability, but there is a large difference in cost, so there are many examples of such partial duplexing.

The difference between FIG. 5 and FIG. 6 is whether the area near the center of the control system is duplicated or the area closer to the field is duplicated.

Recently, the example shown in Figure 5 has been used more often. The reasons for this are: a) The control becomes complicated, the amount of programs and data increases, and as a result, the amount of memory increases, and the reliability of the central part of the control system tends to decrease. on the other hand.

As the reliability of one component has improved in the parts near the field side, overall reliability tends to increase.

b) The package's self-diagnosis function has been enhanced, making it possible to identify defective parts at an early stage. This is especially noticeable in packages closer to the field.

According to etc.

As a result of the increased use of partial redundancy, if a defect occurs in one part, the defective package can be pulled out without turning off the power to the control system, with the power still on. Exchange it for a good item. The so-called hot plug insertion/removal function has become important.

Various measures are taken to ensure that a package does not adversely affect other packages when inserting or removing a stopcock, but in any case, it does not affect the outside of the package itself that is being inserted or removed. We will take measures to prevent this.

In contrast, this circuit operates on the normal side.

This eliminates the influence from the defective side, and is a perfect countermeasure.

Next, the operation of this circuit will be explained using FIGS. 1, 2, and 3.

FIG. 1 is a block diagram of this circuit. FIG. 2 shows an example. Figure 3 is an example of a system in which this circuit is used.

FIG. 3 is a modification of FIG. In Figure 5.

A switch is required between the input/output control package and the input/output package. The input/output control package is usually capable of controlling a plurality of input/output packages, and the connection between the two is a BUS structure.

Therefore, the switch needs to switch a plurality of signals and is complicated, so it is not a good idea to include a switch from both reliability and cost standpoints.

In FIG. 3, the aforementioned switching device is omitted. For that purpose 1
Normally, if the input/output control package on the 110 side is operating, the input/output control package on the 210 side does not need to operate. (This can be easily achieved by setting the power to LOW) If the configuration shown in Fig. 3 is adopted, the normal
While the input/output control package on the 210 side is operating, the input/output control package on the 210 side is in the current state.

If the input/output control package on the 110 side becomes defective, the input/output control package on the 210 side is used. (The selection of the input/output control package will not be discussed as it is not directly related to this case, but it is usually done by software means.) After switching to the 210 side, the 110 side is replaced.

110 and 210 support the same BUS and usually use the same power supply, so replacing 110 inevitably requires hot insertion and removal.Therefore, when inserting or removing 110, the 210 side must be the BUS LOCK. Do this.

FIG. 103 shows a circuit that short-circuits the STB signal to the Vcc side, and when the LOCK signal is active (High), the STB signal is short-circuited to the Vcc side.

02 is a short-circuit current limiting resistor, which is usually several tens of ohms. 01 is the driver for the STB signal. 6 or more is the output side (input/output control package circuit) ) has 32 level shift circuits and 31 buffers.

Next, the normal operation and BUSLOCK method will be described in detail with reference to FIG.

During normal operation, a 100# circuit is used.

At this time, both the I and OCK signals on the 100 side and 200 side are LOW. Therefore, the transistors 103 and 203 are OFF, and the STB signal is.

105.205 to Vcc. At this time, the STB signal on the 100 side is High:
If so, the 101(7) output becomes LOW.

On the other hand, on the receiving side, the input signal became LOW, so 3
The transistor No. 1 becomes 0FFL, and the STB signal becomes LOW.

While the 100 side is operating normally, the STB signal on the 200 side is LOW (because the 200 side is not in use).

Next, when the 100 side becomes defective and the 200 side is used, the same operation as described above occurs.

Furthermore, when the 100 side is exchanged, the 200 side (7) LOCK signal is first set to high level. Then, the transistor 203 is ONL, and the STB signal is Vc.
It is raised to c. Suppose that in this state, the 100 side is extracted, a malfunction occurs during the extraction, and the output of the STB signal on the 100 side becomes LOW. At this time, 200 side Vcc → 2
A current flows through the route of transistor 03 → resistor 102 → driver 101. Therefore, even if the output of 101 is completely Ov, the level on BUS will be Vcc, and the receiving side will not be affected at all.

LOC on 200 side after replacing 100 side with normal package
If the K signal is set to LOW, normal operation is possible again.

Note that the 322 diodes on the 30 side have a level shifting role. This is because when the STB signal on the normal BUS is active (that is, LOW), it is output via the resistor 102 (or 202), so the LO
Since the W level increases, this is necessary to compensate for the increase.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to completely eliminate the influence of malfunctions of other packages on the same BUS.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a detailed circuit diagram of this embodiment, and FIG. 3 is a system diagram of this embodiment.
4 to 6 are diagrams of a duplex system. 01...driver, o2...limiting resistor, 03...
Short circuit speed l Concave υυ IjO force
Figure 5 and input card

Claims (1)

[Claims] 1. Among the packages connected to the bus, in the case where multiple packages can output the same signal to the bus, the connection between the output of the driver circuit in each package and the connection part with the bus. A resistor is inserted in series with the magnetic resistor, and a switch is provided between the magnetic resistor and the connecting portion to short-circuit the operating power supply and the bus, and the switch fixes the bus to the operating power supply voltage. A malfunction prevention circuit characterized in that even if another package is provided and output to the bus, the same signal is invalidated.