18.6.2.9 External Clock

The output clock (GCLK_GEN) of each Generator can be sent to I/O pins (GCLK_IO).

If the Output Enable bit in the Generator Control register is set (GENCTRLn.OE = 1) and the generator is enabled (GENCTRLn.GENEN=1), the Generator requests its clock source and the GCLK_GEN clock is output to an I/O pin.

Note: The I/O pin (GCLK/IO[n]) must first be configured as output by writing the corresponding PORT registers.

If GENCTRLn.OE is 0, the according I/O pin is set to an Output Off Value, which is selected by GENCTRLn.OOV: If GENCTRLn.OOV is '0', the output clock will be low. If this bit is '1', the output clock will be high.

In Standby mode, if the clock is output (GENCTRLn.OE=1), the clock on the I/O pin is frozen to the OOV value if the Run In Standby bit of the Generic Control register (GENCTRLn.RUNSTDBY) is zero.

Note: With GENCTRLn.OE=1 and RUNSTDBY=0, entering the Standby mode can take longer due to a clock source dependent delay between turning off Power Domain PDSW. The maximum delay can be equal to the clock source period multiplied by the division factor.

If GENCTRLn.RUNSTDBY is '1', the GCLKGEN clock is kept running and output to the I/O pin.