Abstract: An automotive sound system achieves manufacturing flexibility by joining a common chassis which implements radio functions with additional boards that are specific to either a cassette, CD, or DAT mechanism which is to be joined with the radio as an integral unit. Each board is controlled by a microcontroller and the separate microcontrollers are connected by a shared bus.

Abstract: An automotive sound system achieves manufacturing flexibility by joining a common chassis which implements radio functions with additional boards that are specific to either a cassette, CD, or DAT mechanism which is to be joined with the radio as an integral unit. Each board is controlled by a microcontroller and the separate microcontrollers are connected by a shared bus.

Abstract: An automotive audio system is provided such that system controls, either pushbutton keypad or rotary switches, connect to an external interrupt pin of a microcontroller capable of restarting the microcontroller from its halt or power-down state. A control activity results in the microcontroller waking up from its halt state, monitoring the system control, and recording system parameter changes in a keep-alive memory. For example, the volume of the system can be changed while the system main power and functions are off. In another embodiment, the microcontroller can be woken up in order to display time-of-day information while both the audio system and the automobile are turned off. After displaying the information or changing the system parameter, the microcontroller returns to its halt state in order to conserve battery power. When the audio system is fully turned on, the most recent parameter setting that was recorded is used to initialize the system.

Abstract: A microcontroller, software-based time-of-day clock compensates for inaccurate oscillator frequency by periodically correcting the time-of-day value using a calibration offset measured by manufacturing test equipment and permanently stored in nonvolatile memory. A high degree of time keeping accuracy is achieved without the use of trimming capacitors or presorted piezoelectric crystals in the oscillator. Furthermore, frequency error compensation is incorporated into the microcontroller system without requiring a significant amount of processing time overhead.