JPS61156337A - Microcomputer-applied device with back-up function for check of input circuit - Google Patents

Abstract

PURPOSE:To shorten the check time by comparing an abnormal state with another input supplied via an input circuit to deliver an output according to the result of said comparison when a program needed for control of an applied device is added to a microcomputer for detection of the abnormal state. CONSTITUTION:A control system of a microcomputer applied device containing a back-up function for check of an input circuit is provided with a 1-chip microcomputer 10 containing a ROM and a RAM, an input circuit 11 which receives the binary signal, an A/D converter 12 for analog signals and an output circuit 13 which delivers digital signals. When the computer 10 is switched to a check mode, an analog signal A is set at an H level that is normally unconceivable. Then only one of input signals B-D is set at an H level with other signals set at L levels respectively. Thus a trouble detection output is delivered in case one or more buffer outputs have different levels since the buffer output is fixed at H or L regardless of the input in a fault mode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to testing technology for microcomputer-applied equipment such as automobile engine control devices, and particularly to detect abnormalities in input circuits that apply external signals to microcomputers in the applied equipment. Related to technology for inspecting the presence or absence of

BACKGROUND OF THE INVENTION In recent years, it has become common to use microcomputers to control various devices. Such microcomputer-applied equipment uses a buffer circuit or an A
/D converter and other input circuits, the microcomputer program performs predetermined calculations, and the output according to human power is sent to external devices via output buffers, etc., and these are controlled. It is something.

By the way, one of the inspections of microcomputer application equipment at the shipping stage is inspection of the input circuit.

This is to check whether there are any abnormalities in the buffer circuits and A/D converters that make up the input circuits, and is particularly important in microcomputer-applied equipment for automobiles, as abnormalities in the input circuits can directly lead to accidents. It is.

Inspection of such input circuits is conventionally performed as follows.

+11 The microcomputer at the shipping stage is operated in the original application equipment control mode in the same way as it actually is.

(2) Microcombi-style - Change one of the inputs added to the evening via the input circuit. Then, the microcomputer reads the change, controls the applied equipment, and outputs the control results. For this reason, some change occurs in the output.

(3) Adjust the state of the output λ, and if it is the same as the state expected when the input is changed, it is determined that there is no abnormality in the input circuit portion corresponding to the input.

(4) Perform the operations (2) and (3) above for other inputs to test other input circuit parts.

Although this method has the advantage of being able to test the input circuit including the validity of the microcomputer control program, it has many problems as follows.

■ Since the microcomputer is operated in applied equipment control mode, if there are some output conditions that do not change until a while after changing the input, it takes time to check and the inspection time becomes longer.

■ Some of the output states are pulse-like and change only for a short time, making it difficult to confirm changes in the output state, which poses a problem in the reliability of inspection.

■ Even if the models have the same power and output, if the microcomputers have different control specifications, it is impossible to use the same testing method, making it difficult to share and automate them.

Problems to be Solved by the Invention The present invention solves these conventional problems, and its purpose is to shorten testing time, improve testing reliability, and enable common testing. be.

Means for Solving the Problems FIG. 1 is an explanatory diagram of the configuration of the present invention, and the present invention is designed to prevent a predetermined signal 1 among the signals input to the microcomputer MPU from being in a state that cannot occur under normal usage conditions. a detection means 3 for detecting that the state of
A comparison means 5 for comparing the state of 2n with a predetermined state, and an output means 7 for outputting a signal according to the comparison result of the comparison means 5 from the microcomputer MPU via the output circuit 6 are provided in the microcomputer application equipment. It is built into the microcomputer MPU.

When testing the action input circuit 4, a predetermined signal 1 among the signals input to the microcomputer MPU is brought into a state that cannot occur under normal usage conditions. For example, a voltage of 5 volts is applied to an input that normally receives a signal of 1 to 4 volts, or two inputs that normally do not go high at the same time are brought to a high level at the same time. Such a state is detected by the detection means 3, and the comparison means 5 is activated.

When a test signal is applied to each of the other inputs 21 to 2n of the microcomputer MPU from the outside via the input circuit 4, the microcomputer MPU reads the signal and stores the state of this signal and a predetermined state, for example, in a memory. It compares signal states or inputs with predetermined signal states in which only one is high level and the others are low level, and outputs the comparison result.

If there is a failure in each part of the input circuit 4, a different signal will be applied from the input circuit 4 to the microcomputer MPU even though a predetermined test signal is applied to the input circuit 4. Since the status signal is different from the status signal of , the input circuit 4 can be inspected for abnormality.

Embodiment FIG. 2 is a block diagram of a control system of a microcomputer-applied device with an input circuit test assisting function according to the present invention.
11 is a so-called one-chip microcomputer having an internal ROM and RAM; 11 is an input circuit that applies a digital signal B-D having a binary state of high level and low level to the input port of the microcomputer 10; and 12 is an input circuit for applying an analog signal A. A/D converter for converting into a digital signal, 1
3 is an output circuit that buffers the output of the microcomputer 10, and EH is a digital output signal.

Input circuit 1] is buffer circuit 11a-l in this embodiment.
Consists of lc. When each buffer circuit is normal, the logic level of digital signals B-D is applied to the microcomputer without changing; however, when a failure occurs, the buffer output is fixed at high or low level regardless of the input. This embodiment uses such a buffer circuit 1.
The purpose is to test for abnormalities in 18-IIC. In this embodiment, the analog signal A is used as the signal for switching the microcomputer 10 to the inspection mode, and the signal E is used as the output for determination. It is up to you which signal from the outputs E-H is used for judgment, but in order to prevent abnormal control from occurring if the product goes into inspection mode during use, it is necessary to avoid any signals that may disturb the original control. Preferably, no or fewer signals are used.

FIG. 3 is a flowchart showing an example of processing by the microcomputer 10. When the microcomputer 10 is powered on, it initializes (S1) and then determines whether the voltage of the analog signal A is 5 volts or more (S2). In this case, the analog signal A is a signal that does not exceed 5 volts during normal operation, that is, during operation when the application device is actually installed in a car or the like and operated.

The microcomputer 10 has a voltage of analog signal A of 5.
If the voltage is at least 5 volts, the test mode processing in steps 83 to S6 is executed, and if it is not at least 5 volts, such processing is not performed and normal application equipment control is immediately executed at step S7. In the state S3, the signals B-D applied from the input circuit 11 are read, and in the step S4, it is determined whether only one of the read signals is at a high level ("H") and the other is at a low level ("Yes"). Determine whether If only one of them is at a high level, one output E is set to a high level (S5), and if not, the output E is set to a low level (S6).

FIG. 4 is a timing chart showing an example of changes in signals AE when testing the buffer circuits 11a to 11c. When testing the buffer circuits 11a-11C, after supplying power to the microcomputer 10 and operating it, the voltage of the analog signal A is first set to 5 volts or more, as shown in FIG. Thereby, the microcomputer 10 executes the processes of steps 83 to S6 at a predetermined cycle. Next, only the signal is set to high level, and signals B and C are set to low level. At this time, buffer circuits 11a to I
If all of the ICs are normal, the signal E goes to a high level as shown by El in FIG. 4. Only the signal B goes to a high level in the 0th order, and then only the signal C goes to a high level.

In either case, if the buffer circuits 11a-'-11C are normal, the signal E becomes high level as shown at E+' in FIG. However, for example, if the buffer circuit 11a fails with its output still at a low level, even if only the signal B is externally applied at a high level, the output of the buffer circuit 11a will remain at a low level and there will be no change, so all inputs will be at a low level. At that time, the output E is E2 in FIG.
Indicates low level as shown in . In addition, the buffer circuit 1
1 If the output of a is at high level and there is a failure, even if only the external signal C or signal B is at high level,
It is determined that two signals, ie and signal C or signal 2, are at high level, and at that time, signal E becomes low level as shown at E3 in FIG. Furthermore, if the outputs of the buffer circuit 11a and the buffer circuit ttb are short-circuited as shown by the dotted line in FIG. 2, one of the signals will not go to high level or low level, so the signal E will go to low level. .

It should be noted that when the microcomputer 10 shown in Fig. 2 is incorporated into applied equipment and is actually operating, the analog signal does not exceed 5 volts, so inspection processing is not performed, and the analog signal Even if the signal exceeds 5 volts and the inspection process is started, the signal E is used, which has no or little risk of disturbing the original control, and the other outputs F-H are used to maintain the original control (step S7). Since the determination is based only on the results and is completely separated from the inspection process, a patent is created that is characterized by abnormal control.

FIG. 5 is a flowchart showing another processing example of the microcomputer 10, and 310-317 indicate each step. The difference from the process in FIG. 3 is step S13 in which it is determined whether the signals B-D are all at high level.
Step S14 of determining whether all signals B-D are at low level; and Step S15 of setting signal E to high level when the conditions of steps 313 and 314 are satisfied, and setting signal E to low level when not satisfied. ．． 51
6. The inspection method in this case is that the signal B-
The state of signal E is confirmed by setting all signals D to high level, and the state of signal E is confirmed by setting all signals B to D to low level.

FIG. 6 is a timing chart showing the states of signals A-E when such a test is carried out.

At time ti, all signals B-D are set to high level, and at time t2
All signals B-D are set to low level. Buffer circuit 1
1 a = 11 If all c are normal, signal E is the 6th
As shown by El in the figure, the high level is maintained during that time. However, if any of the buffer circuits has a failure with the output low level, the signal E will change to the signal B as shown in El in FIG.
Even if all −Ds are set to high level, they remain low level. Furthermore, if any of the buffer circuits is out of order with the output being at a high level, the signal E becomes the signal B-D as shown in E3 in FIG.
Even if all are set to low level, they will remain low level. just
However, in this embodiment, the buffer circuits 11a to llb
A fault in which there is a short circuit between the outputs cannot be inspected. The reason why only the signal C is set to high level at time t1 is to check for an abnormality in the output circuit 13 of the signal E sending system by confirming that the signal E changes to low level at this time.

Although the above embodiment shows an example in which an input circuit having a buffer circuit that handles digital signals is tested for abnormalities, the present invention can also be applied to testing a buffer circuit that handles analog signals and an input circuit that has an A/D converter. Can be applied. In the case of an analog input circuit, for example, a voltage of 5 volts is applied to the analog input circuit, and if a voltage of 5±0.5 volts is applied to the microcomputer, it is determined that there is no abnormality.

As described in detail, according to the present invention, the microcomputer itself to be inspected receives a predetermined signal among the signals input to the microcomputer in addition to the program necessary for the original control of the applied equipment. A detection means for detecting a state that cannot occur under normal usage conditions, and a detection means for detecting each of the other input signals that are activated by the detection of the state by the detection means and input to the microcomputer from the outside via an input circuit. Since a comparison means for comparing the state and a predetermined state and an output means for outputting a signal according to the comparison result of the comparison means from the microcomputer via an output circuit are provided, the following effects can be obtained. be.

(11 Unlike the conventional method of checking the output by changing the input while the microcomputer is performing its original control, processing specifically for inspection is carried out within the microcomputer, so if the input is changed, the output is immediately output.) changes, and the inspection time can be shortened.

(2) Since the output state is maintained while the input is kept in the same state, testing is easy and the reliability of testing can be improved.

(3) As long as the equipment is powered by the same person and has the same output, the same content can be inspected even if the control specifications are different, making it possible to standardize and automate inspections. In addition, the same test can be performed with other models by changing the connector, etc.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of the present invention, Fig. 2 is a block diagram of a control system of a microcomputer application device with an input circuit test assisting function of the present invention, and Fig. 3 is a microcomputer lO
4 is a timing chart showing two sides of changes in signals A-E when testing the buffer circuits 11a to 11c, and FIG. 5 is another processing example of the microcomputer 10. FIG. 6 is a timing chart showing the states of signals A-E when the test shown in FIG. 5 is carried out. 10 is a microcomputer, 11 is an input circuit, 11a
11C is a buffer circuit, 12 is an A/D converter, 13 is an output circuit, and A-H are signals.

Claims (1)

[Claims] detection means for detecting that a predetermined signal among the signals input to the microcomputer is in a state that cannot occur under normal usage conditions; and a detection means activated by the detection of the state of the detection means and input to the microcomputer from the outside. Comparing means for comparing the state of each other input signal inputted through the circuit with a predetermined state; and output means for outputting a signal according to the comparison result of the comparing means from the microcomputer through the output circuit. A microcomputer application device with an input circuit inspection support function, which is built into a microcomputer within the microcomputer application device.