22.4.2.3 Counter Mode

The counter mode is selected by the Timer Counter Mode bit field in the Control A register (CTRLA.MODE). By default, the counter is set to 16-bit counter resolution. Three counter resolutions are available:
  • COUNT8: 8-bit counter mode
  • COUNT16: 16-bit counter mode
  • COUNT32: 32-bit counter mode, achieved by pairing two 16-bit TC instances
    When paired, the TC instances are configured using the registers of the even-numbered TCn. The odd-numbered TCn instance acts as a client, and the Client bit in the Status register (STATUS.SLAVE) will be set. The register values of a client does not reflect the registers of the 32-bit counter. Writing to any of the client registers does not affect the 32-bit counter. Normal access to the client COUNT and CC[n] registers is not allowed.
    Note: If the highest-numbered TCn instance is even-numbered, this instance cannot be configured as a 32-bit counter.