Electronic control unit having user breakable function

Details Electronic control unit having user breakable function Electronic control unit having user breakable function

1999-04-14

2001-01-02

Nguyen, Viet Q. (Department: 2818)

C365S230030, C711S103000

Utility Patent

active

06168321

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application relates to and incorporates herein by reference Japanese Patent Application No. 10-181036 filed on Jun. 26, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic control unit for controlling a predetermined control object, and more particularly to an electronic control unit which is capable of rewriting a control program and the like which are used for controlling a control object such as an internal combustion engine.
2. Related Art
It is known conventionally to use rewritable read only memories such as flash ROMs for electronically controlling a control object. Those flash ROMs generally have a storage area for storing a flash ROM rewriting processing program and a storage area for storing a control program for controlling the predetermined control object. As the content or data stored in the flash ROM is erased or destroyed when the data in those storage areas are rewritten erroneously, a rewriting protection guard is provided in a hardware structure as a function of the flash ROM.
The hardware guard of the flash ROM may be provided block by block. It is therefore not generally possible to guard or protect only a specified storage area in a block. As a result, even if it is tried to rewrite partly and only the stored content in the storage area storing the control program among stored contents of the flash ROM, the rewriting is disabled by the hardware guard. That is, it is necessary to remove the hardware guard even when the partial rewriting is to be executed. Thus, when the hardware guard of the flash ROM is removed to enable rewriting, the stored content will be changed or the stack used to assigns the processing order will be broken, if rewriting is executed erroneously to the storage area storing the rewriting processing program. Thus, subsequent executions of the rewriting processing to the flash ROM will not be enabled any more, if the stored content in the storage area storing the rewriting processing program of the flash ROM is rewritten.
SUMMARY OF THE INVENTION
The present invention therefore has an object to provide an electronic control unit which is capable of prohibiting erroneous processing to a predetermined storage area upon rewriting a stored content of a rewritable read only memory.
According to one aspect of the present invention, an electronic control unit for a control object has a microcomputer and a rewritable read only memory. The rewritable read only memory stores a control program for controlling the control object and a rewriting processing program in its respective storage areas. A user breakable object area is set on the rewritable read only memory by a user breakable function of the microcomputer. Thus, when a data reading command or a data writing command is issued to a predetermined address in a predetermined storage area of the rewritable read only memory, the stored content in the predetermined address is not changed. Instead, the processing jumps to a predetermined other address. Thus, execution of writing to the rewritable read only memory is avoided, even when it arises erroneously due to abnormality.
According to another aspect of the present invention, an electronic control unit for a control object has a microcomputer and a rewritable read only memory. By switching a user breakable object area of the rewritable read only memory between a rewriting processing and a normal processing, only a control program can be rewritten appropriately at the time of the memory rewriting processing. At the time of normal processing, even when the writing is requested to all the storage areas of the rewritable read only memory due to some abnormality, the control program is prevented from being broken or erased and the erroneous operation due to program aberrations is avoided.


REFERENCES:
patent: 5522076 (1996-05-01), Dewa et al.
patent: 5790860 (1998-08-01), Wetmore et al.
patent: 5881295 (1999-03-01), Iwata
patent: 9-128229 (1997-05-01), None

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