JPS644212B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining an abnormality in a microcomputer, which includes a program for the microcomputer to determine an abnormality by itself.

As shown in FIG. 1, when the microcomputer (hereinafter referred to as microcomputer) 10 becomes abnormal, this is notified to the external detection circuit 20 as a change in some signal S output from the output port 11, and a reset is issued from the detection circuit. Microcomputer 10 with signal
There is a method to reset the system. However, in the conventional reset method, the signal S is a simple signal that is output when the microcomputer 10 is operating, and stops when it stops operating, so even if the microcomputer actually malfunctions, the signal S is not output. There are cases where it is determined to be normal and is not reset.

The present invention provides a program-based abnormality detection function on the microcomputer side and actively urges the external detection circuit to reset the system as described above. The present invention creates control data according to a normal processing program of a microcomputer,
An abnormality determination method for a microcomputer in a system for controlling a controlled device, wherein an abnormality determination program is provided as a part of the normal processing program, and the abnormality determination program uses control data for the controlled device as reference data. writing data to a predetermined area in the random access memory; writing data having a predetermined relationship with the reference data to another area in the random access memory; writing the reference data written in the predetermined area and the other area; The method is characterized by comprising a step of determining whether or not the data written in the data has the predetermined relationship, and a step of determining that there is an abnormality when the predetermined relationship does not exist and performing abnormality processing. This will be explained in detail with reference to the drawings.

In the present invention, when the microcomputer 10 is operating normally, the output port 11 of the microcomputer generates an output corresponding to normal operation. This output S may be a simple signal such as an on/off signal with a constant period, or may be a multiple signal pattern having mutual correlation. In the former case, the detection circuit 20 of FIG. 1 only needs to determine whether a specified frequency is generated from the output port 11 using a simple F/V (frequency→voltage) switching circuit. At this time, for example, if the output response of the output port 11 stops, the detection circuit 20 transmits a reset signal to the input port 12 for reset.

In the present invention, the above-mentioned signal S is generated by an internal program of the microcomputer 10. Generally, a 1-chip microcomputer has built-in ROM (read-only memory), RAM (random access memory), internal registers, etc.
Of these, when the ROM is masked, its contents do not change except when the microcomputer is destroyed, so it is not suitable for determining microcomputer abnormalities (mainly malfunctions). On the other hand, the contents of internal registers can change arbitrarily during the operation of the microcomputer, so this cannot be used to determine whether the microcomputer is malfunctioning. The remaining RAM holds data necessary during the operation of the microcomputer, and in particular includes flags directly related to control operations for the controlled equipment, so in the present invention, the operation of this RAM is used to determine whether the microcomputer is abnormal.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 4. Figure 2 shows the inside of the microcomputer 10.
FIG. 3 is an explanatory diagram of the RAM 13. In this example, this RAM
13 specific n addresses (n≧2) A ₁ , A ₂ ,
...Specify A _o for abnormality determination. A control program and a determination program, which will be described later, are included in the normal processing program of the microcomputer 10. The control program first writes reference data D to address _A1 . And the remaining address A ₂ as an example
The same data D or its inverted data is written to ~A _o . In the example shown in Figure 3a, n=3 and the address
This is an example of a control program that writes reference data D to _A1 , the same data D to address _A2 , and inverted data to address _A3 . The operation begins with "A ₁ data rewrite". This means writing reference data D to address _A1 . The next step "A ₂ ←A ₁ " means to transfer the data at address A ₁ , that is, D, to address A ₂ and write the same data there. The final step "A ₃ ← ₁ " means that the data at address A ₁ is inverted and transferred to address A ₃ and written there. Note that the reference data D follows the operation of the microcomputer 10, for example, it is _D1 at the first execution of the control program, _D2 at the second time, _D3 at the third time, etc.
...and may change.

Among the various flags in the RAM 13, address _A1 stores flags that, if modified unrelated to the microcomputer's control operations for the controlled equipment, will cause problems in subsequent control operations. is the address itself. In this case, data D is the flag. Also, put data D in address A ₁ and leave the remaining address Ai (i=
2 to n) may contain any discernable pattern that has a specific relationship with the data D, such as shifting the data D one bit at a time. As in the example in Figure 3, if you put inverted data in a specific address, an error occurs if the contents of that address tend to be easily changed (for example, cleared) in a specific direction due to external noise, etc. This is effective in improving the ability to detect motion.

In this example, a determination program as shown in Figure 3b determines whether a predetermined
Determine whether the relationship between A ₁ and each A _i is correct.
This determination program must be provided in a program loop that is executed periodically whenever there is an abnormality in the RAM data. Such a loop always exists when a system configuration including the aforementioned detection circuit 20 is adopted. When the determination program detects an abnormality, the output S of the output port 11 is changed to a pattern other than that corresponding to normal operation. This allows the detection circuit 20 to detect an abnormal operation and reset the microcomputer 10.

The example of the determination program shown in FIG. 3b determines whether the data in address A ₂ is equal to the data in address A ₁ (if normal, both are D), and if YES, address A ₃ The data inside is the address
Determine whether it is equal to the inverted version of the data in _A1 (or both if normal). If this is also YES, the level of the output port 11 is inverted. Since this is repeated periodically during microcomputer operation, the signal S at the output port 11 during normal operation becomes a pulse train as shown in FIG. On the other hand, an error occurs in the microcomputer and a failure occurs in one of the steps in Figure 3b.
If the signal branches to N, the level of the output port 11 is fixed to H (high) or L (low). Therefore, the detection circuit 20 can detect an abnormality in the microcomputer from the change in the signal S and can generate a reset signal. In this way, since abnormality determination is performed using control data such as flags for controlling controlled equipment, separate digital data is stored in advance for abnormality determination.
Storage devices such as ROM are not required.

FIG. 4 shows a specific example of the detection circuit 20. The input stage of this circuit is an F/V conversion circuit 21, which converts the frequency of the signal S from the output port 11 into a voltage V. 22 is a voltage comparator, which outputs L if the input voltage V is higher than the reference voltage V _ref . This state is when the microcomputer 10 is normal and the level of the signal S is periodically switched to L, H, L, H, etc. (normal pattern). On the other hand, when the level of the signal S is fixed at L or H due to an abnormality in the microcomputer (abnormal pattern), only the DC component becomes available, and the output V of the F/V converter 21 becomes 0. As a result, the output of the voltage comparator 22 rises from L to H, and this rise is used as a trigger signal T to activate the monostable circuit 23. The monostable circuit 23 outputs a signal that temporarily becomes L due to this activation, and resets the microcomputer 10 at the falling edge of the signal.

As described above, according to the present invention, since the microcomputer itself determines whether the data in the RAM is normal or abnormal using its internal program, there is an advantage that not only microcomputer abnormalities but also data abnormalities can be actively detected. Furthermore, unlike a method that performs abnormality determination using data dedicated to abnormality determination stored in a storage device such as ROM in advance, this method uses control data for controlling the controlled equipment to determine abnormality, so it requires less storage space or This can be achieved with the storage capacity.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the system reset method of a microcomputer, Figs. 2 to 4 are diagrams showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the RAM, and Fig. 3 is an explanatory diagram of the abnormality determination program. The explanatory diagram, FIG. 4, is a block diagram showing a specific example of the external detection circuit. In the figure, 10 is a microcomputer, 11 is an output port, and 13 is a RAM.

Claims (1)

[Scope of Claims] 1. A method for determining an abnormality in a microcomputer in a system that creates control data according to a normal processing program of the microcomputer and controls a controlled device, the method comprising: A determination program is provided, and the abnormality determination program includes the steps of: writing control data for the controlled device into a predetermined area in the random access memory as reference data; and writing data having a predetermined relationship with the reference data into other areas in the random access memory. a step of writing in the area; a step of determining whether the reference data written in the predetermined area and data written in the other area have the predetermined relationship; and a step of determining whether or not the reference data written in the predetermined area has the predetermined relationship; 1. A method for determining an abnormality in a microcomputer, the method comprising the step of determining an abnormality and performing abnormality processing.