JPS61262803A - Electronic controller - Google Patents

Abstract

PURPOSE:To protect the memory state of a RAM by inhibiting an access to the backup RAM when a power source voltage drops below the 1st prescribed voltage and resetting a CPU when it drops below the 2nd lower prescribed voltage. CONSTITUTION:A microcomputer 11 including the CPU 12, etc., processes an input signal from an input signal processing circuit 18, and outputs it through an output signal drive circuit 19. Its power source circuit 17 includes a voltage drop detecting circuit 172 and a backup power source 173 as well as a constant voltage circuit 171. When the voltage drop detecting circuit 172 detects that the power source voltage drops below the 1st prescribed value, it applies a nonmaskable interruption to the CPU 12, which inhibits the access to the backup RAM 15. When the power source voltage drops below the 2nd lower prescribed value, the CPU 12 is reset and its action is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used, for example, when electronically controlling an automobile engine, and stores learning data for controlling the engine. The present invention relates to an electronic control device that effectively protects the storage state of M.

[Background Art 1] It is widely practiced to run an automobile engine by an electronic control device using a microcomputer. The microcomputer that constitutes such an electronic control device has a ROM that stores program data, etc., as well as various data for arithmetic operations, as well as learning that corresponds to changes over time, etc. obtained during the control process. There is a backup RAM in which data etc. are stored and set. Important data such as the above-mentioned learning data is transferred to this backup RAM when, for example, the ignition switch is turned off and the power supply voltage is lowered, and even when the power supply voltage is lowered, the stored data is The power supply is set to hold the power. In addition, in such a state of reduced power supply voltage,
The stored contents are protected by prohibiting access from CPtJ. Further, when the power supply voltage returns to the normal state, it is necessary to quickly shift to the normal control processing state.

The means for controlling such backup RAM is as follows:
Although various ideas have been made in the past, for example, in the technology shown in Japanese Patent Laid-Open No. 58-125102, when the power supply voltage drops, a non-maskable signal NMi is generated from a voltage drop detection circuit to send the signal to the CPU. I'm trying to tell you about a voltage drop.

This CPU prohibits access to the backup RAM and sets a flag indicating that the N M i routine has been passed.

In this case, if the voltage drop is instantaneous, the CPU will jump to the lister l-11-res after a certain period of time, and if the flag indicating that the NMi routine has been passed is set, it will be maintained. Clear all RAMs other than the ones that should be removed, and if the above flag is not set, all RAMs are cleared and initialized.

However, with such means, if the voltage drop is instantaneous, the contents of the predetermined memory (RAM) are maintained, but the ignition switch is turned off. In some cases, the stored contents are not retained. Therefore, important data such as character spacing data of past engine control states is not retained, and it is difficult to effectively utilize it for engine control. Furthermore, in the conventional example described above, when the power is momentarily cut off, normal processing cannot be resumed until a specified period of time has elapsed.

[Problems to be Solved by the Invention] This invention has been made in view of the above points. For example, when an engine control device is configured, when the ignition switch is turned off, or The contents of the backup RAM are reliably protected when the power supply voltage drops, such as when the starter motor is started, and especially in the event of a momentary power outage, the contents of the backup RAM are protected as soon as the power supply voltage is restored. The object of the present invention is to provide an electronic control device which allows effective continuity of processing conditions and ensures the protection of important data, such as learning data, for example.

[Means for Solving the Problems] That is, in the electronic control device according to the present invention, when the power supply voltage supplied to the microcomputer is reduced to a state lower than the first voltage set by 1 s, in case of,
This is detected by a voltage drop detection circuit, and access to the backup RAM is prohibited.Furthermore, when the power supply voltage falls below the second voltage, the
The PU is reset-controlled. Then, when the power supply voltage returns, access to the backup RAM is permitted, and if the voltage does not drop until the CPU is reset, arithmetic processing, etc. continues to be executed. It is something that

[Function] That is, when the power supply voltage to the microcomputer drops, first, when the voltage drops below the first set voltage, the backup RAM is set to a state where access is prohibited, and its stored contents are protected. become. In this state, the CPU continues to operate, and if the power supply voltage is restored, the backup RA
Access to tvl is permitted, and processing by CP IJ continues to be executed. Then, a second voltage J whose MmN pressure is set lower than the first set voltage is applied.
The CPU is reset only when the current level drops to a low level.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an electronic engine control unit 1 using, for example, a microcomputer 11 that constitutes an engine control device.
1 includes a CPU 12, a ROM 13 for storing program data, etc., and a RAM 1'4 for storing calculation data, input data, etc. It is equipped with a backup RAM 15 and roughly an A/D converter 16.

For this microcomputer 11, a power supply circuit 1
The power source circuit 17 is set to be supplied with power from the on-vehicle battery B and -1, -BB.

The power supply circuit 17 includes a constant voltage circuit 111 that sets a constant voltage power supply vCC, a voltage drop detection circuit 172 that detects a drop state of the power supply voltage, and a backup power supply circuit 17.
3, the voltage drop detection circuit 172 detects the voltage vth, which is the first set voltage in which the power supply voltage is such that, for example, the access operation of the RAM is not guaranteed, and furthermore, the operation of the CPU 12 is not guaranteed. At a voltage of
Voltage y that is a second voltage lower than a certain first voltage
In the reset state, microcomputer 1
A detection signal is given to 1. Also,
The backup power supply circuit 173 supplies the microcomputer 11 with a backup power supply Vdd.

For the above c p U 12, the human signal processing circuit 1
An input signal suitably converted into a digital signal is supplied via the c p u 12 , and an output signal from the c p u 12 is taken out via an output signal drive circuit 19 .

In an engine control unit using such a microcomputer 11, when the ignition switch is turned on, the power source B from the battery is raised as shown in FIG. 111
The output voltage Vcc rises with a time delay as shown in (B) of the figure. Then, after the power supply voltage VOO exceeds the voltage Vreset that enables the microcomputer 11 to operate, the reset signal becomes active after time t1 has elapsed, and the start control of the c p U 12 is executed. .

Furthermore, when the ignition switch is turned off, the battery voltage element B and the constant N pressure output Vcc are set to the third
It begins to decrease as shown in (A) and (B) of the figure. Then, when the voltage vcc reaches the first set voltage yth, the backup processing interrupt signal becomes active as shown in FIG. 3(C), and the non-maskable interrupt processing for backup is activated. In other words, access to the barrackup RAM 15 is prohibited. Thereafter, when the power supply voltage Vcc further decreases to exceed the second set voltage y reset, the reset signal becomes active as shown in FIG. 3(f), and the operation of the CPU 12 is stopped. It will be stopped.

Furthermore, if the power supply voltage element B is momentarily interrupted as shown in Fig. 4 <A), the voltage VCO that changes in response to this voltage element B is as shown in Fig. 4 (B). like vt
When it becomes less than h, the non-maskable interrupt processing becomes active in the same way as above. And backup RAM15
Access to this RAM 15 is prohibited, and the storage contents of this RAM 15 are protected.

Thereafter, the CPU 12 monitors the state of the cutting signal, and if the voltage VCC returns without falling below the second set voltage V reset, the reset signal does not become active and the c The operating state of p U 12 continues. Then, the voltage Vcc is the voltage V
When the voltage returns to normal without exceeding 1es8t, this voltage Vcc becomes rVth+VhysJ, and the above interrupt signal is canceled. That is, the signal for non-maskable interrupt processing becomes as shown in (C) in FIG. 4, and the reset signal for the CPU 12 does not become active as shown in (D> in the figure), continues to operate.

FIG. 5 shows the flow of processing performed by the microcomputer 11, and particularly shows the normal processing that is started when the CPU 12 is reset.

In other words, with the reset signal active,
First, in step 101, registers, stack pointers, etc. are initialized. Thereafter, in step 102 it is determined whether or not the data has been backed up, and if it is determined that it has been backed up, in step 103 the backup RAM is
Initialize other than 15.

If it is determined in step 102 that the data has not been backed up, all RAMs are initialized in step 104. Thereafter, in step 105, this system is initialized, and in step 106, calculation of the control amount and control are executed.

Figure 6 shows the flow of non-maskable interrupt processing when the power supply voltage drops.When a power supply voltage drop is detected, first, in step 201, the standby (backup) RAM is
15 backup processing is executed. Then, in step 202, it is determined whether or not the power supply voltage has been restored.If the power supply voltage has not been restored, the backup processing described above is continued. If it is determined in step 202 that the power supply voltage has been restored, access to the standby RAM is permitted in step 203, thereby returning to normal operation. However, the continuation process as explained in FIG. 4 is executed.

[Effects of the Invention] As described above, in the electronic control II device according to the present invention, even if the power supply voltage drops for some reason, the backup RAM storing important data can be maintained. The contents are reliably protected, and in the event of a momentary interruption of the power supply voltage, processing can be continued immediately after the power supply voltage is restored.

Therefore, if the engine control unit is constituted by such an electronic control device, a situation where the engine is stopped due to a momentary drop in power supply voltage, for example, can be reliably avoided. Furthermore, since the learning data obtained from past control operations is reliably protected, the engine can be controlled accurately and effectively.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram illustrating an electronic control device according to an embodiment of the present invention, and FIGS. 2 to 4 are signal waveform diagrams illustrating control states corresponding to voltage states of the device, respectively.
FIGS. 5 and 6 are flowcharts each illustrating the flow of control of the above device. 11...Microcomputer, 12...CPLI
, 13... ROM, 14... RAM, 15... Backup (standby) RAM, 17... Power supply circuit. Figure 1 Figure 2 Figure 3 -1 Figure 4 Figure 5 Figure 6 Figure 5TART Voltage drop register or'y or'so 101'
BA ARAM zo1 ho? Nkune sword period II
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Sofa...7F...No
202τ
Kamishi shore voltage. YES 104 17'7A...Z All 70 days AM
Koto era stage 7 speed, 5 RAM 203
Ryofu Komata Fraudomachi System 105 Ne no period 4 Otsu

Claims (1)

[Scope of Claims] A backup RAM configured for a microcomputer and controlled by a CPU, a constant voltage circuit that supplies power to the microcomputer, and a power supply that supplies power to the microcomputer. means for detecting that the voltage has dropped below a first set voltage, and prohibiting access to the backup RAM; and a second set power supply voltage lower than the first voltage.
means for resetting and controlling the CPU of the microcomputer in a state in which the voltage has dropped below the voltage level; a backup power supply circuit configured to supply power to the backup RAM in a state in which the detection circuit detects a voltage drop in the power supply voltage; means for permitting access to the backup RAM in a state in which recovery of the power supply voltage is detected; and means for prohibiting access to the backup RAM in a state in which the power supply voltage has fallen below the first voltage; An electronic control device characterized in that a CPU that controls the RAM is reset-controlled in a state where the power supply voltage has decreased to a second voltage lower than the first voltage.