FB Clock Output not rectangular

[Kolibri]

Hello i´m working with the Development Board FRDMK32L3A6 and i want to use the FB_CLKOUT Pin to clock another Board. Here in this pictures are the settings i use.

Now i´ve measured the Clock Signal with an Oscilloscope and this is what i get. Am i doing something wrong on my measurement or does the clock signal look like this? How can i change it to be rectangular?

Thanks and best regards

[Kolibri]

I think i got it, i have to add a series resistor to the signal i will try it tomorrow.

[Kolibri]

I´ve tried now with different resistors, the signal changes but it´s not gettin rectangular. Can someone please help me to solve this problem. Is there a formula to calculate the series resistor or is it even needed?

Thanks and best regards

[Kolibri · Accepted solution]

The clock signal never looks like a perfect squarewave and it works fine like it is.

Best regards Kolibri