Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-05-28
2001-01-30
Yuen, Henry C. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S115000, C701S102000, C365S185040
Reexamination Certificate
active
06182004
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application relates to and incorporates herein by reference Japanese Patent Application No. 10-189215 filed on Jul. 3, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for controlling memory rewriting operation, and more particularly to an apparatus and method which has a function of holding an electric power supply during rewriting of programs and data stored in a rewritable nonvolatile memory.
2. Description of Related Art
A conventional electronic control unit for controlling a predetermined control object such as an internal combustion engine has a function of holding an electric power supply during a rewriting of a program stored in a rewritable nonvolatile memory. This apparatus is so constructed that a main relay is controlled to hold the electric power supply, thereby preventing a failure of program rewriting due to an accidental interruption of the electric power supply when rewriting data are transmitted from a memory rewriting device connected externally and the program stored in the rewritable nonvolatile memory is rewritten.
When the communication with the memory rewriting device fails or a rewriting processing program in the electronic control unit fails to run normally, the program rewriting is interrupted and the rewriting operation need to be started again from the beginning. If the electronic control unit continues to hold the main relay turned on in this instance, the electric power supply is not stopped and the rewriting processing can not be stopped forcibly even when an ignition switch is turned off.
It is proposed to avoid this problem that the main relay is turned off by the ignition switch when needed. It is however disadvantageous that, when the ignition switch is turned off accidentally during a rewriting of a boot program for initiating the rewriting processing program, the boot program is destroyed disabling the program rewriting again.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a nonvolatile memory rewriting apparatus and method which is capable of setting a hold/stop condition of an electric power supply during a program rewriting in correspondence with the importance or priority of programs stored in a rewritable nonvolatile memory.
According to the present invention, a control program for controlling a predetermined control object and a rewriting processing program including a rewriting program or a boot program, which are stored in storage areas in a rewritable nonvolatile memory and rewritable are rewritten when needed. In this instance, an electric power supply is maintained irrespective of an external interruption operation of the electric power supply, as the rewriting can not be restarted again once the electric power supply is interrupted in the course of rewriting of the rewriting processing program in the nonvolatile memory. On the other hand, the electric power supply is interrupted entirely in response to the external interruption operation of the electric power supply in the course of rewriting the control program in the nonvolatile memory. Thus, the hold/stop of the electric power supply at the time of rewriting can be set based on the importance of programs stored in the nonvolatile memory.
Further, the boot program in the nonvolatile memory is reduced in size to a small one which enables writing of the rewriting program from the outside into a readable/writable volatile memory. Thus, the nonvolatile memory can be reduced in its storage capacity by that reduced amount.
Still further, the nonvolatile memory stores therein a program which controls an electric power control circuit to hold the electric power supply irrespective of the external interruption operation of the electric power supply in the course of rewriting of the nonvolatile memory. The electric power supply is maintained similarly irrespective of the external interruption of the electric power supply during rewriting of the program which controls the electric power control circuit. Thus, as the rewriting of the program which controls the electric power control circuit is not interrupted to prevent program breakage, the electric power supply is ensured during a later rewriting of important programs.
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“Data Integrity of EEPROM Data During Power Up/Down Cycles” IBM Technical Diclosure bulletin, US, IMB Corp. New York, vol. 32, No. 9B, 2/1990 pp. 277-278.
Denso Corporation
Nixon & Vanderhye P.C.
Vo Hieu T.
Yuen Henry C.
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