JPH0546104Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a vehicle control device using a microcomputer.

(Prior art) When configuring a vehicle control device using a microcomputer, abnormality detection using a watchdog timer is used to monitor whether a control program executed by the microcomputer has gone out of control. It is known to incorporate a system (for example, Japanese Patent Application Laid-Open No. 2-40735).

By the way, in the case of such a vehicle control device, there is a demand for monitoring the control state by the microcomputer in addition to monitoring for runaway programs.

In order to meet this requirement, for example, when the microcomputer 1 is used to control a required vehicle system 2 as shown in FIG. This resets the watchdog timer 3 before it reaches an overflow state, causing an abnormality in the operation of the microcomputer 1 and causing the watchdog pulse WD to be output from 1a.
When the microcomputer 1 is no longer output at a predetermined period, the watchdog timer 3 outputs a reset pulse RP and the microcomputer 1 is reset. Monitor signal MS indicating control status
A configuration for outputting the signal and supplying it to the monitor signal reading device 4 is known.

(Problem to be solved by the invention) According to this conventional configuration, a port for outputting watchdog pulses and a port for outputting monitor signals are required separately, which causes problems in terms of effective use of the ports. If one port is assigned to each output signal, even if there is no shortage of ports, a problem arises in that the load on the software increases.

Therefore, an object of the present invention is to provide a microcomputer-based microcomputer capable of controlling a watchdog timer and monitoring the operating status of the system using the output from a single port. The purpose is to provide a control device.

(Means for Solving the Problems) A feature of the present invention for solving the above problems is that it controls a vehicle system according to a predetermined control program, and also outputs a monitor signal indicating the control state of the vehicle system. In a vehicle control device using a microcomputer that is configured to output the monitor signal to the outside, it is possible to identify a set of data using a start bit and a stop bit set to different levels of the monitor signal. The present invention is characterized in that a watchdog timer is provided which continuously outputs the bit-serial digital data and is reset in response to at least a level change between the stop bit and the start bit in the monitor signal.

(Operation) During normal operation, the microcomputer continuously outputs a monitor signal at a predetermined period. Therefore, since the predetermined level change necessarily occurs periodically between the stop bit and the start bit, the watchdog timer is at least reset in response to this, and the watchdog timer does not become overflowed. . In addition,
If the same level change as the predetermined level change occurs in the data, this also resets the watchdog timer. This monitor signal is
Further, the control state can be monitored based on the monitor signal inputted to an appropriate monitor circuit.

On the other hand, if the control program goes out of control and becomes abnormally operating, the output of the monitor signal stops or the output cycle becomes longer.
The reset operation for the watchdog timer is no longer performed as planned, and the watchdog timer overflows, resetting the microcomputer.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In FIG. 1, 11 is a microcomputer, 12 is a vehicle air conditioning system which is a vehicle system controlled by the microcomputer 11, and 13 is a watch. The clock timer 14 is a monitor signal reading device.

A control program for controlling the vehicle air conditioning system 12 is stored in the memory 15 in the microcomputer 11, and a control program for controlling the vehicle air conditioning system 12 is stored in the memory 15. The output status signal A (not shown) is input to the microcomputer 11. The microcomputer 11 executes data processing according to the control program based on the status signal A, and the microcomputer 11 outputs a control signal B for controlling the vehicle air conditioning system 12.
is controlled by control signal B.

The microcomputer 11 has a function of outputting a monitor signal MS indicating a required operating state of the vehicle air conditioning system 12 according to a control program stored in the memory 15, and the monitor signal MS is It is output from the output port 11a.

The monitor signal MS is as shown in FIG.
The signal for one data consists of a start bit SR at "L" level, data bit DB consisting of 8 bits, parity bit PB, and stop bit at "H" level.
Consists of ST. It is bit serial digital data. The monitor signal MS is a signal in which a set of data configured in this way is continuously connected, and a start bit SR at an "L" level always appears after a stop bit ST at an "H" level. become. Therefore, a level change from "H" to "L" always occurs in the monitor signal MS before the time T required for transmitting a signal for one data is exceeded.

This monitor signal MS outputted from the output port 11a is connected to the input of a buffer amplifier 19 via a resistor circuit consisting of resistors 17 and 18, and its output is connected to the monitor signal reading device via a resistor 20. 14 is input. The monitor signal reading device 14 decodes the contents of the monitor signal MS, and the result is displayed on the display device 21.

As explained based on Fig. 2, the monitor signal
MS is the time T required to transmit a signal for one data
It has a property that the level always changes from "H" to "L" before the monitor signal MS
By using this property, watchdog timer 1
The configuration is such that the reset operation described in No. 3 is performed.

That is, the monitor signal MS output from the output port 11a is applied to the watchdog pulse input terminal 13a of the watchdog timer 13 via the capacitor 16, and the watchdog timer 13 receives the monitor signal MS. "H" →
It is configured to be reset when a change in the level of "L" occurs.

As already explained, since the monitor signal MS changes in level from "H" to "L" at least every time T, the watchdog timer 13 is reset at a cycle shorter than the time T. The time X from when the watchdog timer 13 is reset until it enters an overflow state and a reset pulse RP for resetting the microcomputer 11 is output from its output terminal 13b is set longer than the time T. Therefore, the control program is running normally and the monitor signal MS
As long as RP is continuously output, the reset pulse RP will not be applied to the reset terminal of the microcomputer 11. However, if the output of the monitor signal MS is stopped due to a runaway of the control program, or if it is not output in a predetermined format even if it is output, the watchdog timer 13 becomes overflowed and is reset to the terminal of the microcomputer 11. The microcomputer 11 can be reset by applying the pulse RP.

Furthermore, as can be seen from the above explanation, the monitor signal
In the MS, the signal changes from "H" to "L" except between the stop bit ST and start bit SR.
However, even if the watchdog timer 13 is reset due to this, no problem will occur.

According to the above configuration, by sending a monitor signal in a predetermined format to the outside from one output port, it is possible to not only monitor the control state but also control the watchdog timer 13 at the same time. be able to. Therefore, not only can the program load on the microcomputer 11 be reduced, but also the number of ports used can be reduced, and the remaining ports can be used for other purposes, resulting in greater design freedom. It has advantages such as increased strength.

Although the above embodiment shows an example in which the present invention is used to control a vehicle air conditioning system, the present invention is not limited to the configuration of this embodiment.
The present invention can be similarly applied to any vehicle control system.

(Effects of the invention) According to the invention, as described above, the control state can be monitored and the watchdog timer can be controlled by the monitor signal output from one output port of the microcomputer. In addition to reducing the program load, the number of ports used can be reduced, and the remaining ports can be used for other purposes, resulting in increased design freedom. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a diagram showing the format of a monitor signal output from the output port of the microcomputer shown in FIG. 1, and FIG. 3 is a block diagram showing an example of the configuration of a conventional device. 11...Microcomputer, 11b...Output port, 12...Vehicle air conditioning system, 1
3...Watchdog timer, 14...Monitor signal reading device, MS...Monitor signal, SR...Start bit, ST...Stop bit.

Claims (1)

[Scope of utility model registration request] In a vehicle control device using a microcomputer configured to control a vehicle system according to a predetermined control program and output a monitor signal indicating a control state of the vehicle system to the outside, The monitor signal is continuously output as bit-serial digital data in which a set of data can be identified by the start bit and stop bit set to different levels, and the stop bit and stop bit in the monitor signal are 1. A vehicle control device using a microcomputer, characterized in that it is provided with a watchdog timer that is reset in response to at least a level change between the start bit and the start bit.