JP3925196B2 - Vehicle electronics - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular electronic apparatus having a plurality of microcomputers (hereinafter abbreviated as microcomputers), and more particularly to a reset control method thereof.
[0002]
[Prior art]
In recent years, it has been studied to reduce the operating voltage of a microcomputer in order to reduce battery consumption, and it is considered that microcomputers having different operating voltages are mixed in one vehicle electronic device (ECU). In this case, microcomputers having different operating voltages naturally have different minimum operating voltages, and a plurality of microcomputers having different minimum operating voltages are used in one electronic device. As a reset control method for such a vehicle electronic device, there is a method in which all microcomputers are reset at the threshold value of the microcomputer having the highest minimum operating voltage when the power supply voltage is lowered.
[0003]
For example, in the configuration shown in FIG. 4, the electronic device 30 includes microcomputers 31 and 32 and a reset generation circuit 33, and the operating voltage of the microcomputer 31 is 3.3 V and the operating voltage of the microcomputer 32 is 5 V as an example. In this case, the minimum operating voltage of the microcomputer 31 is lower than the minimum operating voltage of the microcomputer 32. The reset generation circuit 33 monitors a power supply voltage (specifically, a 5V output of a constant voltage circuit (not shown)) and outputs a reset signal to the microcomputers 31 and 32 when the power supply voltage drops to a predetermined reset voltage. In this case, the reset voltage is set based on the microcomputer 32 having the higher minimum operating voltage, and all the microcomputers 31 and 32 are simultaneously reset when the voltage drops.
[0004]
According to the above configuration, when the power supply voltage decreases, the microcomputer 32 having the higher minimum operating voltage becomes abnormal, and the malfunction that the electronic device 30 malfunctions due to the abnormality is prevented.
[0005]
[Problems to be solved by the invention]
However, in the above prior art, the reset voltage of the electronic device 30 depends on the minimum operating voltage of the microcomputer 32, and the voltage level of occurrence of reset becomes high. Therefore, for example, when the power supply voltage temporarily decreases when the engine is started, the microcomputers 31 and 32 are likely to be reset. In this case, since the microcomputer 31 with the lowest minimum operating voltage is also reset at the same time, there arises a problem that the performance as the electronic device 30 is impaired.
[0006]
The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to provide a vehicle electronic device that can appropriately control resetting of a plurality of microcomputers and realize desired control performance. Is to provide.
[0007]
[Means for Solving the Problems]
The vehicle electronic device according to claim 1 includes a plurality of microcomputers having different minimum operating voltages. The low voltage reset circuit monitors the power supply voltage and outputs a reset signal to the microcomputer when the power supply voltage drops to a predetermined reset voltage. In particular, the low-voltage reset circuit has a plurality of reset voltages for each microcomputer having a different minimum operating voltage and outputs a reset signal for each microcomputer.
[0008]
According to this configuration, for example, when the power supply voltage temporarily decreases at engine start, not all the microcomputers are reset at the same time, but the microcomputers are individually reset according to the reset voltage set for each microcomputer. . In this case, the performance of each microcomputer can be realized without depending on a microcomputer having a high minimum operating voltage. As a result, it is possible to appropriately control resetting of a plurality of microcomputers and achieve desired control performance.
[0009]
In the first aspect of the present invention, when a microcomputer having the lowest operating voltage among the plurality of microcomputers monitors a reset signal to the microcomputer having the lowest operating voltage, and the microcomputer having the highest operating voltage is in the reset state, another of the microcomputer in the active state,
a. Fail-safe execution to supplement the operation of the microcomputer in the reset state,
b. Prohibition of communication abnormality determination based on communication data when communicating with the microcomputer in the reset state,
c. Prohibition of the monitoring process when monitoring the operation for the control output of the microcomputer in the reset state,
The process proceeds to at least one process. In this case, the other microcomputer can detect that one of the microcomputers has been reset first, and the a. ~ C. It is possible to shift to at least one process. Therefore, even when the microcomputer in the active state and the microcomputer in the reset state coexist, the electronic device operates properly.
[0011]
A. Accordingly, it is possible to continue the control with the microcomputer in the active state while guaranteeing the operation on the microcomputer side in the reset state. Therefore, the operation of the electronic device in a low voltage region is guaranteed .
[0012]
When communicating between microcomputers, if one of them is reset, communication cannot be performed correctly. In this case, b. Accordingly, erroneous communication abnormality determination can be prevented. Further, when monitoring the operation of the control output between the microcomputers, if the monitored microcomputer (the microcomputer with the highest minimum operating voltage) is in a reset state, the control output of the microcomputer is different from the normal state. In this case, the above c. Accordingly, erroneous determination of control output abnormality can be prevented.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a vehicle electronic device according to the present embodiment.
[0014]
In FIG. 1, an electronic device 10 controls various control objects, and has two microcomputers (first microcomputer 11 and second microcomputer 12) having different minimum operating voltages. The first microcomputer 11 and the second microcomputer 12 are connected via a communication line 13 so that they can communicate with each other. For example, the electronic device 10 is an automobile engine ECU, the first microcomputer 11 is a microcomputer that performs fuel injection control and ignition timing control, and the second microcomputer 12 is a microcomputer that performs electronic throttle control. In this case, for example, the operating voltage of the first microcomputer 11 is 3.3 V, and the operating voltage of the second microcomputer 12 is 5 V. Therefore, the minimum operating voltage of the first microcomputer 11 is higher than the minimum operating voltage of the second microcomputer 12. It is low.
[0015]
The power supply IC 14 is provided with two constant voltage circuits 15 and 16, and a battery voltage is supplied to each of the constant voltage circuits 15 and 16. The constant voltage circuit 15 generates an operating voltage V1 (= 3.3V) for driving the first microcomputer 11, and the constant voltage circuit 16 generates an operating voltage V2 (= 5V) for driving the second microcomputer 12. To do.
[0016]
The constant voltage circuit 16 for generating the operating voltage V2 (= 5V) is connected to two reset generation circuits 17 and 18 as "low voltage reset circuits". The operating voltage V2 is monitored and a reset signal is output to the microcomputers 11 and 12 when V2 drops. In this case, the reset generation circuit 17 outputs a reset signal to the reset terminal of the first microcomputer 11, and the reset generation circuit 18 outputs a reset signal to the reset terminal of the second microcomputer 12. Incidentally, the monitoring of the operating voltage V2 by the reset generation circuits 17 and 18 monitors the power supply voltage of each of the microcomputers 11 and 12.
[0017]
Here, a reset voltage (threshold voltage) Vth1 corresponding to the minimum operating voltage of the first microcomputer 11 is set in the reset generating circuit 17, and the minimum operating voltage of the second microcomputer 12 is set in the reset generating circuit 18. A corresponding reset voltage (threshold voltage) Vth2 is set. Vth2> Vth1, and when the operating voltage V2 decreases, the second microcomputer 12 is reset before the first microcomputer 11. The reset voltages Vth1 and Vth2 are set to voltages slightly higher than the minimum operating voltages of the microcomputers 11 and 12.
[0018]
The first microcomputer 11 monitors a reset signal from the reset generation circuit 18 to the second microcomputer 12. In the power supply IC 14, the outputs (V 1, V 2) of the constant voltage circuits 15, 16 are input to the respective reset generation circuits 17, 18, the reset generation circuit 17 monitors the operating voltage V 1, and the reset generation circuit 18 operates at the operating voltage. It may be configured to monitor V2.
[0019]
Next, an outline of reset control in each of the microcomputers 11 and 12 will be described. FIG. 2 is a flowchart showing the reset monitoring process performed by the first microcomputer 11. This process is performed by the first microcomputer 11 at a predetermined time period (for example, a period of 4 msec).
[0020]
In FIG. 2, first, in step 101, it is determined whether or not the second microcomputer 12 is in a reset state. If the second microcomputer 12 is not in the reset state, the process proceeds to step 102 to instruct to perform the fuel injection control and the ignition control as usual, and then this process is terminated.
[0021]
If the second microcomputer 12 is in the reset state, the process proceeds to another processing mode. That is, in step 103, a predetermined fail-safe process is performed to supplement the operation on the second microcomputer 12 side. Specifically, as fail-safe processing related to electronic throttle control, reduction cylinder control for stopping fuel injection in some cylinders and ignition delay for retarding ignition timing in order to realize vehicle retreat travel (limp home). Implement control, etc. In addition, the fuel injection amount and the ignition timing may be corrected so that an engine stall does not occur due to a decrease in the engine speed when the second microcomputer 12 is reset.
[0022]
Thereafter, in step 104, communication abnormality determination with the second microcomputer 12 is prohibited. That is, the first microcomputer 11 performs communication abnormality determination based on communication data (received data from the second microcomputer 11) via the communication line 13, but when the second microcomputer 12 is in a reset state, communication is caused by that. Cannot be implemented correctly. Therefore, communication abnormality determination is prohibited.
[0023]
In step 105, the control output abnormality determination related to the second microcomputer 12 is prohibited. That is, the first microcomputer 11 monitors the state of electronic throttle control by the second microcomputer 12, and for example, depending on whether or not the control output by the second microcomputer 12 matches the actual operation state of the throttle actuator, Make a decision. In this case, when the second microcomputer 12 is in a reset state, the control output of the microcomputer 12 is different from that in a normal state. Therefore, control output abnormality determination is prohibited.
[0024]
FIG. 3 is a time chart showing the state of reset control when the operating voltage is lowered.
In FIG. 3, when the operating voltage V <b> 2 decreases to the reset voltage Vth <b> 2 (timing t <b> 1), the second microcomputer 12 is reset by the reset generation circuit 18. At this time, the first microcomputer 11 confirms that the second microcomputer 12 has been reset.
[0025]
When the operating voltage V2 further decreases to the reset voltage Vth1 (timing t2), the first microcomputer 11 is reset by the reset generation circuit 17. In this case, the first microcomputer 11 is in the active state and the second microcomputer 12 is in the reset state during the period from the timing t1 to t2, and the above-described fail-safe processing or the like is performed (steps 103 to 105 in FIG. 2). That is, another process based on the premise that the second microcomputer 12 is stopped in the first microcomputer 11 is performed, and the control operation as the electronic device 10 is continued.
[0026]
For example, when the operating voltage V2 temporarily decreases due to the fluctuation of the battery voltage when starting the engine, only the second microcomputer 12 is reset when the operating voltage V2 reaches the reset voltage Vth2. In addition, only the second microcomputer 12 is first reset when the operating voltage V2 decreases due to battery deterioration or the like. In such a case, since not all the microcomputers are reset at the same time, the control operation in the low voltage region is improved.
[0027]
According to the embodiment described in detail above, the following effects can be obtained.
(A) Since the microcomputers 11 and 12 are individually reset by the reset voltage set for each of the microcomputers 11 and 12, without depending on the microcomputer having the highest minimum operating voltage (the second microcomputer 12 in the present embodiment). , Individual microcomputer performance can be realized. As a result, it is possible to appropriately control the resetting of the microcomputers 11 and 12 and realize a desired control performance.
[0028]
(B) When the second microcomputer 12 is in the reset state, the first microcomputer 11 detects that and shifts to another process. Therefore, even when the active state microcomputer and the reset state microcomputer coexist, the electronic device 10 Works properly.
[0029]
(C) When the second microcomputer 12 is in the reset state, reset guarantee control (fail safe processing) is performed, so that the electronic device 10 is guaranteed to operate in a low voltage range.
[0030]
(D) Since the communication abnormality determination between the first and second microcomputers 11 and 12 is prohibited when the second microcomputer 12 is in the reset state, erroneous communication abnormality determination by the first microcomputer 11 can be prevented.
[0031]
(E) Since the monitoring process for the second microcomputer 12 is prohibited when the second microcomputer 12 is in the reset state, erroneous determination of control output abnormality by the first microcomputer 11 can be prevented.
[0032]
In addition to the above, the present invention can be embodied in the following forms.
In the configuration of FIG. 1, the low-voltage reset circuit is configured by the two reset generation circuits 17 and 18, but this may be changed. For example, a configuration in which one reset generation circuit is provided and the circuit has two reset voltages (threshold voltages), or a configuration in which the reset voltage is switched to two stages may be employed. When switching the reset voltage, first, the reset voltage Vth2 corresponding to the minimum operating voltage of the second microcomputer 12 is set, and after the second microcomputer 12 is reset with the reset voltage Vth2, the minimum operation of the first microcomputer 11 is performed. Switching to the reset voltage Vth1 corresponding to the voltage. However, the reset state of the second microcomputer 12 may be maintained even after the reset voltage is switched.
[0033]
In the above-described embodiment, the present invention is embodied in a vehicle electronic device having two microcomputers, but can also be applied to an electronic device having three or more microcomputers. For example, when three microcomputers having different minimum operating voltages are provided, it is preferable to set three reset voltages according to each microcomputer and output a reset signal for each microcomputer. In this case, the microcomputer having the lowest minimum operating voltage may monitor the reset signals of the other two microcomputers. Alternatively, the microcomputer having the second lowest operating voltage may monitor the reset signal of the microcomputer having the highest lowest operating voltage, and the microcomputer having the lowest lowest operating voltage may monitor the reset signal of the microcomputer having the second lowest operating voltage. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a vehicle electronic device in an embodiment of the invention.
FIG. 2 is a flowchart showing reset monitoring processing.
FIG. 3 is a time chart showing how reset control is performed when the operating voltage drops.
FIG. 4 is a block diagram illustrating a configuration of an electronic device according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Electronic device, 11 ... 1st microcomputer, 12 ... 2nd microcomputer, 14 ... Power supply IC, 17, 18 ... Reset generation circuit.

Claims (1)

A vehicle electronic device comprising: a plurality of microcomputers having different minimum operating voltages; and a low voltage reset circuit that monitors a power supply voltage and outputs a reset signal to the microcomputer when the power supply voltage drops to a predetermined reset voltage. The low voltage reset circuit has a plurality of reset voltages for each microcomputer having a different minimum operating voltage and outputs a reset signal for each of the microcomputers. monitoring a reset signal to the high operating voltage range microcomputer, when the minimum operating voltage high microcomputer is reset, the other microcomputer in the active state,
a. Fail-safe execution to supplement the operation of the microcomputer in the reset state,
b. Prohibition of communication abnormality determination based on communication data when communicating with the microcomputer in the reset state,
c. Prohibition of the monitoring process when monitoring the operation on the control output of the microcomputer in the reset state,
The vehicle electronic device is characterized in that it shifts to at least one of the following processes.

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