The brownout circuit is implemented to provide the proper internal reset signal to the device during power on and power off. The supply voltage supervisor (SVS) circuitry detects if supply voltage drops below a user-selectable level and supports both supply voltage supervision (the device is automatically reset) and supply voltage monitoring (SVM) (the device is not automatically reset).
The CPU begins code execution after the brownout circuit releases the device reset. However, VCC may not have ramped to VCC(min) at that time. The user must make sure that the default DCO settings are not changed until VCC reaches VCC(min). If desired, the SVS circuit can be used to determine when VCC reaches VCC(min).