JPS6093502A - Output holding system of digital controller - Google Patents

Abstract

PURPOSE:To secure a minimum necessary output state without placing an output signal in an abnormal state even in case of a fault by providing a fault-time output register, and setting the same data with a normal-time output register therein periodically. CONSTITUTION:The fault-time output register 3 is provided in addition to the normal-time output register 2, and the same data is set periodically. If the output register 2 gets out of order or if the data in the register 2 is destroyed, a fault detecting circuit 5 generates a fault-time switching signal, an output switching circuit 4 selects the data in the fault-time register 3, and an output circuit 6 outputs an output signal from a terminal. Thus, the fault-time output register 3 is provided to maintain a minimum necessary output state without putting the output signal in an abnormal state even in case of a fault, so damage to a process to be controlled is prevented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an output holding method for a digital control device that makes it possible to maintain the minimum required output state for a controlled object even when the digital control device fails. .

[Prior art]

Conventionally, there has been a system of this type as shown in FIG. 1
2 is an output register for setting digital signals, and 6 is an output circuit for outputting data held in the output register.

Next, the operation will be explained. MicroProcera t1 is
Periodically set a digital signal to output register 2,
Update the data to be output. The output circuit 6 outputs the data held in the output register 2, and an output signal can be taken out from the output terminal.

In the conventional output holding method, the data in the output register 2 is output as is, so if the output register 2 fails or the data in the output register 2 is destroyed,
This has the drawback of causing a situation where the output becomes abnormal.

In particular, in a digital control device, unlike an analog control device, which automatically returns to the original normal state in response to a disturbance, it is difficult to return to the original state, so abnormal output may cause serious damage to the process. For this reason, there is a need for a system that can instantly monitor abnormal power consumption and prevent major changes in the process even when a failure occurs.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is a digital control device that prevents the output signal from going into an abnormal state even in the event of a failure and ensures the minimum required output state. The purpose is to provide a method for maintaining

(Example of the invention) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, l is a microprocessor, 2 is an output register that stores data that should be output during normal operation, 3 is a failure output register that stores data that should be output in the event of a failure, and 4 is the output register 2. 5 is a failure detection circuit that generates a switching signal to switch the output switching circuit 4, and 6 is the output switching circuit. This is an output circuit that outputs a selected output.

Next, the operation will be explained. Microprocessor 1 is
Digital signals are periodically set in the output register 2 and the failure output register 3 to update the data to be output. During normal operation, the data held in the output register 2 is passed through the output switching circuit 4 to the output circuit 6, and an output signal can be taken out from the output terminal. At this time, if the output register 2 fails or the data in the output register is destroyed, the failure detection circuit 5 generates a failure switching signal, and the data in the failure output register 3 is selected by the output switching circuit 4. The output circuit 6 outputs an output signal from the terminal.

If the same data is periodically set in the output register 2 and the failure output register 3, even if the data in the output register 2 is destroyed, the data before the failure will be output.

FIG. 3 is a block diagram of an output holding system for a digital control device according to another embodiment of the present invention.

In FIG. 3, 2 is an output register, 4 is an output switching circuit, 6 is an output circuit, and 7 is a switching signal generating circuit. In the embodiment shown in FIG. 2, the output switching circuit 4 is switched by the fault switching signal detected by the fault detection circuit 5, whereas the third
In the illustrated embodiment, the output circuit 4 is switched by an output signal from an arbitrary switching signal generating circuit. Further, the number of output signals to be switched is not limited to two, and switching of multiple outputs is also possible. Further, a microprocessor is not necessarily required, and the digital control section may have any configuration as long as it can set data in the output register.

〔Effect of the invention〕

As described above, according to the present invention, even in the event of a failure, the output signal of the digital control device does not become abnormal, and the minimum required output state can be maintained, so that it is possible to maintain the minimum required output state. It has the effect of being able to control it without causing any damage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an output holding method of a conventional digital control device, FIG. 2 is a block diagram showing an output holding method of a digital control device according to an embodiment of the present invention, and FIG.
The figure is a block diagram showing an output holding system of a digital control device according to another embodiment of the present invention. 1... Microprocessor, 2... Output register,
3...Failure output register, 4...Output switching circuit,
5... Failure detection circuit, 6... Output circuit, 7... Switching signal generation circuit. Note that the same reference numerals in the figures indicate the same parts. Agent Masuo Oiwa Procedural Amendment (Voluntary) 1. Indication of the case: Japanese Patent Application No. 58-202072 2, Title of the invention: Digital control device appearance retention system 3, Person making the amendment Representative Hitoshi Katayama Department 4, Agent 5, Details of the invention in the specification to be amended Explanation column 6, page 4, line 6 of the description of the contents of the amendment, ``through'' is amended to ``selected by''. that's all

Claims (1)

[Claims] An output register that holds the output data of the digital control device during normal operation, an output register at the time of failure that holds the output data of the digital control device at the time of failure, and each data of the above-mentioned output register or output register at the time of failure. An output holding system for a digital control device comprising: an output switching circuit that selects an output switching circuit; a failure detection circuit that supplies a fault switching signal to the output switching circuit; and an output circuit that outputs output data of the output switching circuit.