hardware//I/O//MMIO

Memory-mapped I/O (MMIO) is a method of hardware access in which device registers are mapped into the CPU's address space so that they look like ordinary RAM locations, and it lets a program drive peripherals with plain reads and writes. A write to `0x4000_1000` might toggle a GPIO pin; a read from `0x4001_0004` might fetch an ADC sample.

Memory-mapped I/O (MMIO) is a method of hardware access in which device registers are mapped into the CPU's address space so that they look like ordinary RAM locations, and it lets a program drive peripherals with plain reads and writes. A write to 0x4000_1000 might toggle a GPIO pin; a read from 0x4001_0004 might fetch an ADC sample.

MCU programming is largely MMIO, and the STM32 and ESP32 SDKs provide register-level abstractions over the MMIO addresses.