MCKn Clock Frequency

When the I²S is in Master mode, writing a '1' to CLKCTRLn.MCKEN will output GCLK_I2S_n as Master Clock to the MCKn pin. The Master Clock to MCKn pin can be divided by writing to CLKCTRLn.MCKSEL and CLKCTRLn.MCKOUTOUT. The Master Clock (MCKn) frequency is GCLK_I2S_n frequency divided by (MCLKOUTDIV+1).

f(MCKn)=f(GCLK_I2S_n)(MCKOUTDIV+1)