JPS59200323A - Backup confirmation device for memory backup device of in-vehicle microcomputer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a memory backup device for a vehicle-mounted microcomputer, and more particularly to a device for confirming memory backup.

BACKGROUND ART For example, an on-vehicle microcomputer that centrally controls an internal combustion engine mounted on a vehicle requires data from the previous operation when starting its operation.

Even after the power supply to the CPU (Central Processing Unit) is stopped by turning off the ignition switch, this type of in-vehicle microcomputer continues to supply power to the RAM (Random Access Memory) from the battery via the backup power supply circuit. It has a memory back amplifier device that holds data in the RAM until it is activated.

However, in this type of memory backup device, if the power supply to the RAM is interrupted due to the microcomputer unit being removed from the vehicle or the power line being disconnected, the data stored in the RAM will not be retained correctly. Then, the next operation of the microcomputer is performed based on this incorrectly stored data, so that proper operation control is not performed.

In this way, in conventional in-vehicle microcomputers, the memory contents of RAM read at the start of operation are FLAM.
The above-mentioned inconvenience occurs because reading is performed without confirming whether or not the device has been destroyed due to the power supply being cut off.

Therefore, in order to avoid such inconvenience, the present invention provides a backup confirmation device that confirms whether data stored in the RAM has been destroyed due to the power supply to the RAM being stopped when the in-vehicle microcomputer starts operating. The purpose is to provide

<Summary of the Invention> For this purpose, a transmitting means for emitting a signal for a period from the time when a battery is connected to a single-mounted microcomputer until a predetermined time has elapsed after the first power supply to the on-vehicle microcomputer is turned on, and a power source for the on-vehicle microcomputer are provided. A back amplifier confirmation device is configured, which includes a detection means for detecting whether or not the signal is transmitted when the signal is turned on.

According to this, the signal is emitted within the predetermined time period from the time when the microcomputer is powered on for the first time after the power supply to the memory backup device is resumed, and the signal emission is then stopped, so that the signal is emitted for the second and subsequent times. When the microcomputer is powered on, the signal is not being transmitted.

In other words, the signal is sent when the microcomputer starts operating for the first time after the power supply is restarted when the memory contents of R and AM are not held correctly, and from the second time onwards after the power supply is restarted when the memory contents of RAM are correctly held. When the microcomputer starts operating, the signal is not being transmitted. Therefore, if the above signal is detected when the microcomputer starts operating, it is determined that the correct data is not stored in the RAM, and the microcomputer does not operate accordingly. or prevented.

Example The present invention will be explained below based on an embodiment shown in FIG.

Specifically, in the figure, the CPU 1, l10 (input/output signal processing device) 2, and ROM (read-only memory) 3 include:
Power is supplied from the battery 4 via an ignition switch 5 and a power supply circuit 6, and power is further supplied to the RAM 7 via a diode D1. In addition, RAM 7 contains the ignition switch 5.
Power is supplied to the memory back amplifier through a constant voltage backup power supply circuit 8 consisting of a Zener diode Z, a resistor R1, a capacitor C1, and a diode D2. And these CPU1
, l102, ROM3, and RAM7, signals are exchanged between them via the bus 9, as in the conventional case.

Here, a voltage obtained by dividing the battery voltage branched from before the diode D3 and the resistor R2 by the resistors R3 and R4 is input to the inverter 10.
A diode D4 and a capacitor C2 are connected in parallel to the resistors Ra and R4, respectively, and set time constants for the rise and fall of the voltage input to the inverter 1o. The output of this ear A-1o is input to a set terminal 11a of a flip-flop circuit 110 serving as a signal transmitting means.

The flip-flop circuit 11 is composed of two NOR games) 11b
, 11c, and a resistor R is connected to the reset terminal 11d from the power supply circuit 6.
The terminal voltage of the capacitor C3, which is charged via the capacitor C3, is inputted.

The output terminal 11e is the l1 of the microcomputer.
Connected to 02.

The power supply circuit 6 is turned on by turning on the ignition switch 5.
After starting power supply to U1, l102 and J: and ROM3, 1
After a delay of about 00 milliJ seconds, power supply is started for reset. Here, the time constant determined by the values of the resistor R5 and the capacitor C3 is determined by the reset terminal of the flip-flop circuit 11 when a predetermined time has elapsed after the microcomputer was powered on. Select such that the 1d voltage reaches the reset voltage.

The CPU 1 includes a signal detection means for detecting whether the output voltage of the flip-flop circuit 11 is at a high level or a low level during a period of time after the power is turned on until the predetermined time period elapses.

Note that the inverter 10 and the flip-flop circuit 11
Power is supplied through the backup power supply circuit 8.

Effect Next, the effect will be explained with reference to a time chart (shown in FIG. 2) showing changes in voltage at each point indicated by lower case letters in FIG.

If the power supply to the memory backup device is restarted after being stopped, such as when the on-vehicle microcomputer unit is removed from the vehicle and then reattached to the vehicle and the battery 4 is connected, As shown in FIG. 2 (5), the voltage at the point becomes equal to the battery voltage as soon as the battery 4 is connected, and this state continues until the battery 4 is removed again.

When the power supply is resumed, the inverter 10. flip-flop circuit 11 and R,
A predetermined constant voltage is now applied to AM7. As shown in FIG. 2(B), the voltage applied to the inverter 10 and the flip-flop circuit 11 reaches a predetermined voltage value after a certain delay time has elapsed after the power supply is restarted, and these two circuits become operational. .

On the other hand, the battery voltage charges the voltage dividing capacitor C2 through the resistor Rs and 14. The terminal voltage of this capacitor C2, that is, the voltage at a point in FIG. 1, increases with a time constant determined by resistors R3 and R4 and capacitor C2, as shown in FIG. The output of 1o, that is, the voltage at point C in Figure 1, becomes high level at the same time as the power supply starts, as shown in Figure 2 (to), and sets the flip-flop circuit 11, and then the long voltage, that is, the voltage at point b, becomes the operating voltage. When it exceeds , it becomes low level.

d in FIG. 1, which is the output of this flip-flop circuit 11.
As shown in Figure 2, the voltage at the point becomes high level almost immediately after the power supply is resumed, and is input to l102.Here, when the ignition switch 5 is turned on, the power supply circuit 6 first starts supplying power to the microcomputer. After that, after a delay of about 10 milliseconds, charging of the capacitor C3 starts via the resistor 'EL5 (Fig. 2 (F)).
, (see Gl).

As a result, the reset terminal voltage of the slip-flop circuit 11, that is, the voltage at point e in FIG. 1, increases with a time constant determined by the resistor Rs and the capacitor c3, as shown in FIG. When the reset voltage is reached over time, the flip-flop circuit 11 is reset (
FIG. 2 (see diagram) Sets its output to low level.

The output voltage of the flip-flop circuit 11 is at a high level for a predetermined time (time indicated by Tl in FIG. 2) after the ignition switch f5:#7 is turned on for the first microcomputer operation after power supply is resumed. . On the other hand, the output voltage of the flip-flop circuit 11 within a predetermined time after turning on the ignition switch (time indicated by T2 in FIG. Since it is reset by turning on switch 5, it becomes low level.

After turning on the ignition switch 5, the CPU 1 is activated within the predetermined time (the time indicated by "1tT2" in Fig. 2).
The output voltage of the flip-flop circuit 11 is detected by the signal detecting means, and if it is at a high level, the memory contents of the RAM have been destroyed, and on the other hand, if it is at a low level, the RA
It can be determined that the memory contents of M are not destroyed.

If it is determined that the memory contents of the RAM have been destroyed, the microcomputer will not set the data in the RAM as the initial value (it will operate by setting a new initial value, so if the data is incorrect) This prevents malfunctions based on

In this embodiment, the necessary means are constructed from electric circuits, but these means may be constructed from a second micro combinator which operates according to a program stored in a non-volatile memory.

Effects> As explained above, in the present invention, since the backup confirmation device is configured to emit a signal if the memory contents of the RAM are destroyed when the on-vehicle microcomputer is powered on, this signal can be detected. This makes it possible to take appropriate measures, preventing the on-vehicle microcomputer from operating based on incorrect data, and ensuring reliable computer control.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an embodiment of the present invention, Figure 2 -
are time charts showing changes in voltage or state at each point shown in FIG. 1, respectively. 1... CPU 2... Engineering 10 3... ROM
4...Battery 6...Power circuit 7...R
AM8...Backup power supply circuit 10...Inverter 11...Flip-flop circuit R5...
Resistor C8... Capacitor Patent Applicant Japan Electronics Co., Ltd. Agent Patent Attorney Fujio Sasashima

Claims (1)

[Claims] In an in-vehicle microcomputer that has a memory backup device that retains data by supplying power to the RAM of the microcomputer from a battery via a backup power supply circuit, the in-vehicle microcomputer is powered on for the first time from the time the battery is connected to the in-vehicle microcomputer. An in-vehicle microcomputer comprising: signal transmitting means for emitting a signal for a period of time until a predetermined time elapses; and signal detecting means for detecting whether or not the signal is being emitted when the in-vehicle microcomputer is powered on. A backup confirmation device in a computer memory backup device.