Hello everyone! I have a question here attached.The one underlined in blue is that tx because to my knowledge tx is the settling time measured in nanoseconds.

 

The way that's worded, I would take it as propagation time, which would include settling time, of any logic between, or pre-FF1 and/or FF2 - it is not the same as tx, see this paper from TI: https://www.ti.com/lit/an/scza004a/scza004a.pdf

 

Ok thank you! So in my question,it will be e to the power of K1 times tx which is calculated as 20ns over tau.And the formula for tau is 1/2pi *25MHz?

 

Hmmm, tau in that equation is equal to 1/K1 in your equation, and therefore tr is your tx.

 

Ah ok thank you! so to put it simply its just e^tr*K1

 

I was simply comparing terms. and their description, between two equations. You must satisfy yourself of their equivalences, and that you understand them & how to use the equation(s).