FIELD PRESETTABLE ELECTRONIC USEMETER

摘要

An electronic odometer (10) which is field presettable within limits after it is installed in a vehicle. A microprocessor (14) is utilized to store a total accumulated mileage (odometer) signal in a non-volatile random access memory (RAM) (19). The microprocessor retrieves stored odometer signals, loads them into a microprocessor contained volatile memory (14a), increments the volatile memory odometer signal in accordance with signals from an actual mileage sensor (11) and displays the odometer signal on display (24). The magnitude of the odometer signal stored in memory (19) can be preset to a predetermined mileage after the non-volatile memory is coupled to microprocessor (14). This presenting can only be implemented a maximum of three times and only if 10 driven mileage storage location (22) in non-volatile memory (19) indicates that the vehicle in which the odometer is installed has been driven less than ten miles. Wherein the signals in ten driven mile storage location (22) cannot be preset. In response to a substantial (more than ten mile) adjustment of the odometer signal stored in the non-volatile memory (19), an overflow flag is non-volatilely stored and this results in the odometer display providing a visual indication (at 26) that a substantial adjustment of the odometer signal in the non-volatile memory (19) has occurred. The presetting of the odometer signal in non-volatile RAM (19) is accomplished through utilization of the trip and units manual controls (15-17), and the vehicle ignition switch (12).