46.6.3.3 Transfer Rate Clock Source

The TWIHS speed is defined in the TWIHS_CWGR. The TWIHS baud rate can be based either on the peripheral clock if the CKSRC bit value is ‘0’ or on a GCLK clock if the CKSRC bit value is ‘1’.

If CKSRC = 1, the baud rate is independent of the system/core clock (MCK) and thus the MCK frequency can be changed without affecting the TWIHS transfer rate.

The GCLK frequency must always be three times lower than the peripheral clock frequency.