2 Overview

The flexible 16-bit PWM Timer/Counter type A (TCA) provides accurate program execution timing, frequency and waveform generation, and command execution.

A TCA instance consists of a base counter and three compare channels. The user can set the base counter to count upwards or downwards based on clock ticks (timer) or different events (counter). The Event System can also be used for direction control or to synchronize operations. The period can be adjusted from a specific register as well as the compare thresholds that can be used to generate different waveforms or to trigger events. It is worth mentioning that a prescaler can be used to divide the clock source and also that TCA can operate in Idle sleep mode.

The counter value is compared continuously to zero and the period value. If one of the conditions is met, the control logic block acts according to the configured operation mode, updating the counter and/or generating an interrupt request. The counter is also compared to the Compare registers. Use these comparisons to generate interrupt requests and set the waveform period or the pulse width if a Waveform Generator mode is selected. The Counter, Period and Compare registers and all their buffers are 16 bits wide. The buffers are part of a scheme that ensures the respective registers are updated only when the Counter register is updated. Each buffer has a Buffer Valid (BV) bit used by the logic block to determine if the respective register needs to be updated.

The TCA can be configured to use the Event System and can be utilized to count rising and/or falling edges of the event signal or use it to enable clock ticks counting. Also, the polarity of the event signal can be used to control the direction, low signal for up-counting, and high signal for down-counting. Moreover, the TCA can generate one-cycle strobes on the event channel outputs. The trigger for generating one-cycle strobes on the event channel can be the overflow of the timer, a compare channel match, or an underflow in Split mode.