Resets

Resets are events or operations that return a system to a defined initial state. They are used to recover from faults, reinitialize hardware and software components, and prepare devices for normal operation after power changes or errors. Resets can be physical, logical, or timed, and may affect only part of a system or its entire state.

Hardware reset is typically initiated by a dedicated reset input, a reset button, or a power cycle. It clears volatile state and causes peripherals and controllers to reinitialize as the device starts up. Soft reset is software-initiated and often preserves non-volatile data while reinitializing software layers.

Power-on reset occurs when power is first applied and uses a reset circuit to ensure a known state before software runs. Watchdog resets are produced by a watchdog timer that triggers a reset if software becomes unresponsive. Brown-out or low-voltage resets occur when supply voltage falls below a threshold.

In practice, resets may be local to a subsystem or global to the whole device, and some systems support multiple reset domains with different scopes. In software and user interfaces, a reset typically clears values and returns components to their default configurations. In hardware, a reset can be essential for recoveries after faults.

They differ from restarts in that resets aim to restore initial conditions at the hardware or software state level, while restarts may simply reinitialize sequences without guaranteeing a full reset of all state. Design considerations include ensuring safe recovery, minimizing data loss, preventing accidental resets, and providing appropriate feedback to users.