JPS62168244A - Detecting circuit for abnormality of microcomputer - Google Patents

Abstract

PURPOSE:To lead a control subject to the safety side by means of hardware when the abnormality of a microcomputer is produced, by actuating the control subject based on the output of an abnormality detecting circuit that is designated by the microcomputer for each fixed period of time. CONSTITUTION:A CPU 1 outputs an address showing an abnormality detecting circuit 4 for each fixed time and data to a data bus 10 by programs. Here a pulse generating means 6 produces the data pulses which are rectified and integrated by a rectifying/integrating means 7. When the output voltage level of the means 7 exceeds the 1st threshold value V1, a Schmitt trigger means 8 actuates a power relay 9 to attain the energization to a heater 12. If the CPU 1 has the abnormality such as a runaway, etc., no data pulse is produced and the output voltage level falls. When this voltage is less than the 2nd threshold value V2, the operation of the relay 9 is stopped and the energization is stopped to the heater 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a microcomputer abnormality detection circuit for detecting an abnormality in a microcomputer in, for example, measurement or control equipment.

(b) Conventional technology If a microcomputer stops operating or runs out of control due to some reason, such as a momentary power outage, external noise, defective parts, or poor soldering during mounting, it may cause damage to the control system or control equipment. Among those used,
This may lead to irreversible accidents. Therefore, in order to prevent accidents from occurring, it is well known to use a momentary power failure detection circuit that detects momentary power outages based on changes in power supply voltage, and a line filter in the power supply unit to prevent external noise.

(c) Problems to be solved by the invention However, in order to control the object to be controlled after a power outage is detected,
In order to return the controlled object to the safe side, a program different from the normal control program is required, and if the microcomputer is malfunctioning, there is a risk of loss of control.

That is, when the object to be controlled is a heater, for example, the microcomputer controls a triac (thyristor) or the like to energize the heater. In this case, when direct current is applied to ensure ignition without applying a pulse to the gate of the triac, a data latch circuit is included in the heater drive circuit. If the microcomputer stops or runs out of control due to a momentary power outage, the data may remain latched in the data latch circuit and not be reset, or even if the pulse is erased, the pulse may be lost due to abnormal operation of the microcomputer. may remain visible. In these cases, normal feedback control is not performed and the heater continues to be energized, so there is a risk of overheating.

This invention was made in view of the above-mentioned circumstances, and it constantly checks whether the microcomputer is operating normally, and if an abnormality occurs, it is possible to use a separate hardware circuit without going through the microcomputer. The present invention aims to provide an abnormality detection circuit for a microcomputer that can return a controlled object to a safe state.

(d) Means for Solving the Problems The configuration of the present invention is such that an address is specified repeatedly from a microcomputer at regular intervals, and
pulse generating means for generating pulses based on input data; rectifying and integrating means for rectifying and integrating the pulses; and rectifying and integrating means for rectifying and integrating the pulses; This is an abnormality detection circuit for a microcomputer, characterized by comprising a Schmitt trigger means for outputting a control signal to stop the operation of the microcomputer.

(E) The pulses output by the action pulse generating means are rectified and integrated by the rectifying and integrating means, and the Schmitt trigger means operates the controlled object when the output voltage is above a certain value, and operates the controlled object when the output voltage is below the certain value. to stop something from working.

(F) EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following examples.

FIG. 1 shows an embodiment of the present invention, which is connected to a microcomputer (hereinafter referred to as CPU) that controls energization of a heater, which is an object to be controlled, provided in a heating section of a gas chromatograph, for example.

(1) is a CPU, and an address decoder (3) is connected to its address bus (2). (4) is an abnormality detection circuit, which is connected to the address decoder (3) via a NAND gate (5). The abnormality detection circuit (4) is connected to a pulse generating means (6) such as a one-shot multivibrator that generates pulses, and is connected to the pulse generating means (6) to rectify and integrate the pulses output by the pulse generating means (6). and a Schmidt trigger means (8) which is connected to the rectifier and integrates the rectifier and which activates the power relay (9) according to the output voltage value of the rectifier and the rectifier. 5) is for negating the address and the data from data bus 00. (11) is a NAND gate whose respective inputs are connected to address decoder (3) and data bus ω). The output of the NAND gate (11) is connected to the heater surface drive circuit 03).

Heater surface and heater a? A relay contact (9a) of a power relay (9) is connected in series between the J AC power source (14). The driving means 03 is composed of, for example, a data latch circuit (not shown) that latches data from the NAND gate (11J) and a triac (or thyristor) (not shown) that is connected to the data latch and controls energization of the heater surface. Ru.

Next, the operation of this embodiment will be explained.

The CPU (11 is a program that is placed in the background routine) runs the abnormality detection circuit (4) at regular intervals.
) and output the data. When the abnormality detection circuit (41) is designated by an address, the pulse generating means (6) generates a data pulse (15) as shown in FIG.
] is rectified and integrated by the rectification and integration means (7) at the next stage and inputted to the Schmitt trigger means (8). Schmitt trigger means (8) actuates the power relay (9) when the rectifying and integrating means (output voltage of force) exceeds the first threshold value v1, so that the relay contact (9a) activates the ONL heater az
It becomes possible to energize. In this state, the CPU fil is operating normally.

If the CPU [1] malfunctions for some reason, such as runaway, the malfunction detector circuit (4) is not addressed and therefore the pulse generating means (6) no longer generates data pulses 05). Data pulse 05)
When the value of the output voltage (16) decreases and becomes equal to or less than the second threshold value (2) of the Schmitt trigger means (8), the operation of the power relay (9) is stopped. Therefore, relay contact (9a) stops energizing the 0FFL heater az. In this case, even if the heater drive circuit 0'3I is active, energization to the heater surface is stopped and overheating is prevented.

In Figure 2, area (A) is the range where CPU (11) is operating normally, and area (B) is CPU fl).
Indicates a case where something goes wrong.

In the above embodiment, the program for specifying addresses is placed in a background routine, but it may be placed in an interrupt routine. However, by placing it in a background routine, excessive interrupts can cause the background routine to be serviced by 4f.
Even when the number of uaf decreases, the CPU [
11 abnormalities can be determined and its effectiveness is enhanced.

(G) Effects of the Invention According to the present invention, it is possible to obtain an abnormality detection circuit for a microcomputer that can constantly check for abnormalities in the microcomputer and can guide the controlled object to a safe side using hardware when an abnormality occurs. Furthermore, since control after an abnormality is not performed by software, it is possible to effectively detect an abnormality even if the microcomputer goes out of control.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a heater energization control circuit including an abnormality detection circuit according to an embodiment of the present invention, and FIG. 2 is an explanation explaining the respective output waveforms of the pulse generation means and the rectification/integration means and the operating state of the microcomputer. It is a diagram. (1)...Microcomputer (CPU). (4)... Abnormality detection circuit, (6)...
Pulse generation means. (Katana... Rectifying and integrating means. (8)... Schmitt trigger means. Fig. 1

Claims (1)

[Claims] 1. A pulse generating means that is specified by an address repeatedly specified by a microcomputer at regular intervals and generates a pulse based on input data, a rectifying and integrating means that rectifies and integrates the pulse, and an output voltage of the rectifying and integrating means. 1. An abnormality detection circuit for a microcomputer, comprising Schmitt trigger means for outputting a control signal to a controlled object to stop the operation of the controlled object when the value becomes below a certain value.