2 docs tagged with "power-loss"

A supply does not fail like a light switch. Pull the plug, drop a battery connector, or let a coin cell finally reach the end of its discharge curve, and VDD does not fall to zero — it decays, over a span set by whatever capacitance is still holding charge on the rail and whatever the circuit is still drawing from it. That decay is the entire subject of this page, because it is the only thing standing between "the supply is gone" and "the core has actually stopped running," and the honest answer to "how long do I have" is: a lot less than most designs assume, and the amount is calculable rather than a matter of taste.

Flash is not memory that happens to be non-volatile. It is a device with an asymmetric write model, and every design decision about storing settings on an MCU comes out of that asymmetry: you can clear a bit at any time, cheaply, one word at a time — but you cannot set a bit back to 1 without erasing an entire sector, which takes up to two seconds, during which the processor cannot fetch instructions from the same flash it is executing from.