The dsPIC33 devices integrate many of the necessary system maintenance features. For system integrity, there is a watchdog timer that will reset the device if allowed to time out or will also reset if cleared too early. To save power in the system, there are 3 low power modes. Idle mode will stop CPU execution while allowing selected peripherals to continue to run. Doze mode will slow the CPU execution will allowing the peripherals to continue to run at normal speed. Finally, sleep mode will shut down all operation on the device while maintaining the state of the machine when it is awakened by a peripheral event. There are several options for clocking the devices. In addition to the normal external sources and crystal oscillators, these devices contain a precision internal RC oscillator that is accurate to within plus or minus 2%. These devices also contain a phase locked loop that can accept an external source, a crystal or the precision on board RC oscillator as source and multiply it for high speed operation.