Vehicle diagnosis system
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United States of America Patent
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-
Dec 26, 1995
Grant Date -
N/A
app pub date -
Jun 14, 1994
filing date -
Jun 17, 1993
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
In a vehicle diagnosis system in which a diagnosis unit is connected to a control unit, the control unit determines whether or not there is a code read request from the diagnosis unit. When there is the request, it further determines whether or not code erase is in execution. When code erase is not in execution, an abnormality code stored in the standby RAM region of its CPU is searched for and the result is transmitted to the diagnosis unit. When code erase is in execution, on the other hand, the data after code erase (no abnormality code) is transmitted to the diagnosis unit. Thus, during code erase operation, the abnormality data before erase is prevented from being transmitted to the diagnosis unit. Further, in case of a RAM value read request is made from a main CPU to other CPU in the controller, it is checked whether a requested address value from the main CPU to the other CPU agrees with the address value transmitted from the other CPU to the main CPU. When the address values agree, the flag XA4ANS is set. After a prescribed interval from this flag setting, the RAM value corresponding to the requested address are responsively sent out to the diagnosis unit. Therefore, transmission of erroneous information to the diagnosis unit can be prevented without fail.
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