Apparatus and method prohibiting RAM diagnosis when other...

Details Apparatus and method prohibiting RAM diagnosis when other... Apparatus and method prohibiting RAM diagnosis when other...

1999-08-16

2001-09-25

Verbrugge, Kevin (Department: 2185)

Electrical computers and digital processing systems: memory

Storage accessing and control

Control technique

Reexamination Certificate

active

06295589

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a diagnosis apparatus and a diagnosis method of a RAM to be used in a microcomputer for controlling various electronic controlled devices in an engine of a vehicle and the like.
DESCRIPTION OF THE RELATED ART
Conventionally, in a control apparatus of an engine mounted on a vehicle, in addition to the self-diagnosis performed by the CPU in the control microcomputer, a diagnosis of the ROM or RAM and the like are performed by the CPU (refer to Japanese Unexamined Patent Publication No. 64-19401).
The diagnosis of the RAM is performed as follows. At every predetermined diagnosis timing, interruption is first prohibited so as to prevent rewriting of the RAM, and then, a read/write check is performed to the diagnosis object RAM by previously determined diagnosis unit bytes (four bytes for example) at a time.
However, due to the CPU construction, when hardware other than the ALU (arithmetical and logic unit) has a function to access the RAM directly, the RAM being diagnosed may be rewritten irrelevantly to orders from the ALU, which will lead to erroneous diagnosis.
For example, when the main CPU and the sub CPU are connected through a communication line, the RAM may be rewritten by a DMAC (direct memory access controller) in the CPU according to communication. Since the DMAC has a high interrupt level, such rewriting of the RAM cannot be prevented even by prohibiting interrupt.
The present invention aims at solving the above-mentioned problem. The object of the present invention is to prevent erroneous diagnosis caused by a case where hardware other than the ALU (arithmetical and logic unit) has a function to access the RAM directly, due to the construction of the CPU.
SUMMARY OF THE INVENTION
In order to achieve the above object, a diagnosis apparatus of a RAM according to the present invention, including a RAM diagnosis device for diagnosing a RAM by a read/write method at every predetermined diagnosis timing and an interrupt prohibiting device for prohibiting interrupt during diagnosis, comprises an external interrupt monitoring device for monitoring a status of external interrupt where hardware other than an arithmetical and logic unit accesses the RAM, and a diagnosis prohibiting device for prohibiting the diagnosis by the RAM diagnosis device when it is determined by the monitoring device that the status enables external interrupt.
According to this construction, the diagnosis of the RAM is prohibited during the state in which external interrupt may occur where hardware other than the ALU (arithmetical and logic unit) may access the RAM. Thereby, erroneous diagnosis caused by a case where the diagnosed RAM being diagnosed may be rewritten irrelevantly to orders from the ALU may be prevented, and the reliability of the RAM diagnosis may therefore be improved.
Further, when the RAM diagnosis device is to perform diagnosis to a diagnosis object RAM by previously determined diagnosis unit bytes at a time, the diagnosis prohibiting device may be not only to prohibit the diagnosis of the diagnosis object RAM, but also to store the address of the diagnosis object RAM in a memory, and to have the diagnosis object RAM diagnosed at a next diagnosis timing.
Accordingly, when the RAM diagnosis is prohibited, the address of the diagnosis object RAM at that time is stored in a memory, and the RAM is diagnosed at the next diagnosis timing, so as to guarantee diagnosis.
The external interrupt monitoring device may be set to monitor whether a start-up of a DMAC (direct memory access controller) is approved or not as the status of external interrupt.
As above, by monitoring whether the start-up of the DMAC (direct memory access controller) is approved or not as the external interrupt status, situations enabling the rewriting of the RAM by the DMAC can be detected assuredly.
Actually, the RAM diagnosis device may be constituted to save data of the diagnosis object RAM to a buffer by previously determined diagnosis unit bytes at a time, and on the other hand, copy the data of the diagnosis object RAM to a temporary, bit-reverse the temporary data, and stores the reversed temporary data to the diagnosis object RAM, before determining whether or not the data of the diagnosis object RAM and the data of the temporary correspond.
Further, the RAM diagnosis device may determine whether or not the data of the diagnosis object RAM and the data of the buffer correspond, after returning the data of the buffer to the diagnosis object RAM.
The RAM diagnosis according to the present invention may advantageously improve the reliability of engine control by making the RAM used in a microcomputer for controlling an engine mounted on a vehicle a diagnosis object.
Characteristic features of the present invention and the resultant function and effects will become more apparent from the following description of embodiment given in conjunction with the appended drawings.


REFERENCES:
patent: 5036516 (1991-07-01), Cordell
patent: 5479347 (1995-12-01), Oguro et al.
patent: 5829015 (1998-10-01), Maeno
patent: 64-19401 (1989-01-01), None

Affiliated with

Also associated with

Rating

Apparatus and method prohibiting RAM diagnosis when other... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Apparatus and method prohibiting RAM diagnosis when other..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method prohibiting RAM diagnosis when other... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2495403