Onboard control system for controlling devices installed on motor vehicle and method or rewriting control program and variables therefor

A vehicle-onboard control system installed on a motor vehicle for controlling at least one device mounted on said vehicle, comprising:

• a central processing unit (11) for executing a control program by using various control variables to thereby control said device (40) mounted on said motor vehicle;
• a writable non-volatile read-only memory (12) for storing said control program;
• a backup random access memory (14) for storing said control variables;
• a backup power supply (30) for supplying electric power to said backup random access memory (14);
• a bootstrap program (13) for operating said central processing unit (11) to rewrite said control program;
• an address changing interface (15) for locating said bootstrap program (13) at an address executable by said central processing unit (11) upon rewriting of said control program;
• and
• a memory rewriting device (50) for outputting a rewrite signal (A) for actuating said address changing means interface (15) and a command signal (C) for activating said bootstrap program (13);
• wherein said control program, after have been rewritten, compares a decision reference value stored in said writable non-volatile read-only memory (12) with a predetermined value stored in said backup random access memory (14) to thereby initialize said backup random access memory (14) when discrepancy is detected between said decision reference value and said predetermined value;
• said bootstrap program responding to said command signal (C) to thereby update said decision reference value to an abnormal value;
• and
• wherein said control program initializes said backup random access memory (14) in response to a discrepancy between said abnormal value and said predetermined value upon activation of said control program after having been rewritten.

A vehicle-onboard control system installed on a motor vehicle for controlling at least one device mounted on said vehicle, comprising:

• a central processing unit (11) for executing a control program by using various control variables to control said device (40) mounted on said motor vehicle;
• a writable non-volatile read-only memory (12) for storing said control program;
• a backup random access memory (14) for storing said control variables;
• a backup power supply (30) for supplying electric power to said backup random access memory (14);
• a bootstrap program (13) for operating said central processing unit (11) to rewrite said control program;
• an address changing interface (15) for locating said bootstrap program (13) at an address executable by said central processing unit (11) upon rewriting of said control program;
• and
• a memory rewriting device (50) for outputting a rewrite signal (A) for actuating said address changing (15) and a command signal (C) for activating said bootstrap program (13);
• wherein a control variable processing flag (FC) adapted to be set in response to said command signal (C) upon rewriting of said control program is provided;
• said memory rewriting device (50) outputting a control variable data signal (D) together with said command signal (C);
• said command signal (C) containing a control variable initialize command;
• said control variable data signal (D) containing a number (n) of data for rewriting said control variable, a start address (ADS) for the rewriting and data for initialization (DN);
• said control variable processing flag (FC) being set up in response to said control variable initialize command;
• wherein upon rewriting of said control program, said bootstrap program (13) responds to the set state of said control variable processing flag (FC) to thereby initialize in accordance with said data (DN) for initialization the control variables stored at memory locations of said backup random access memory (14) which are determined by said number (n) of the data for rewriting and said rewrite start address (ADS).

A method for rewriting a control program stored in a writable non-volatile read-only memory (12) provided in a vehicle-onboard control system installed on a motor vehicle for controlling at least one device mounted on said vehicle, which system further includes a central processing unit (11) for executing the control program by using control variables to thereby control said device (40) mounted on said motor vehicle, a backup random access memory (14) for storing said control variables, a bootstrap program (13) for operating said central processing unit (11) to allow interrupt processing routines to be executed thereby, and a switching device (15) for changing over said bootstrap program and said control program with one another for execution by said central processing unit,

• the method for rewriting said control program stored in said writable non-volatile read-only memory (12), comprising the steps of:
• issuing a command signal (A, C, D) for activating said bootstrap program to rewrite said control program;
• and
• providing information for allowing an altered control program resulting from said rewriting to initialize said control variables so that said control variables conform with said altered control program.