EC / SIO basics: power, reset, and keyboard controller duties

Embedded controller (EC / KBC) overview in plain English (rewritten from common bench teaching points). What the EC usually owns - Power button debounce, some always-on enables, keyboard/trackpad matrix, fan PWM, battery charging handshake, and often shared SPI with BIOS regions. When to suspect the EC - No reaction to power button, missing ALW rails that the EC should enable, keyboard dead while USB power is present, or charge light stuck. Checks - EC VCC, reset release, crystal/clock present. - Firmware: do not erase the whole chip unless you have a verified dump for that board revision. BoardView helps locate the EC package (often Nuvoton / ITE / ENE) and its flash. Pair with the schematic power sequence pages.