capturecompare

Capture/compare (CC) units are timer peripherals found in many microcontrollers that provide two related functions: capture of input events and comparison of a timer count with stored values to trigger actions. They are commonly used to generate timed waveforms, measure signal properties, and coordinate events in real time. A CC unit is typically part of a larger timer module and may include multiple independent channels, each configurable for input capture or output compare, and often capable of PWM generation.

In input capture mode, the current timer count is latched into a capture register when a selected input edge occurs (rising, falling, or both). The captured timestamp can be used to determine input period, pulse width, or frequency, usually with interrupts or direct memory access for software processing.

In output compare mode, the timer value is compared against a configured compare value. When the timer reaches the match, the CC channel can drive an output pin, toggle or set/clear the output, or generate an interrupt or peripheral event. In PWM applications, the compare value sets the duty cycle while the timer’s top or period defines the overall signal period.

Hardware details vary by device but typically include a prescaler, a counting register, a period (top) value, and multiple channels that can be configured independently. Features may include edge selection, output polarity, dead-time insertion (in advanced timers), and per-channel interrupts.

Common uses include PWM for motor and LED control, servo positioning, and precise timing or measurement of external signals. The exact terminology and capabilities of capture/compare units differ among microcontroller families.