Introduction
The process of starting any microcontroller is a non-trivial one. The underlying hard- ware is complex and a small, manufacturer-defined ‘reset routine’ must be run to place this hardware into an appropriate state before it can begin executing the user program. Running this reset routine takes time and requires that the microcontroller’s oscillator is operating.
Where your system is supplied by a robust power supply, which rapidly reaches its specified output voltage when switched on, rapidly decreases to 0V when switched off, and – while switched on – cannot ‘brown out’ (drop in voltage), then you can safely use low-cost reset hardware based on a capacitor and a resistor: this form of reset circuit is addressed in RC RESET [page 68].
Where your power supply is less than perfect, and / or your application is safety related, the simple RC solution will not be suitable. ROBUST RESET [page 77] discusses a more reliable alternative.