Microstrip Crosstalk Calculator: Does Length of Parallel Routes Mean Net Length or Track Width?

Dear forum, I have a question about microstrip crosstalk calculator from eeweb (https://www.eeweb.com/tools/microstrip-crosstalk) I attached figure with input parameters I desire to know. Im designing a 2 layer pcb and Im going to use ethermet module, which use W5200 chip. As far as I know, the speed of my SPI SCLK pin on master configuration reaches 80Mhz and for slave 20Mhz. From W5200 datasheet, it says for stable operation at least 33Mhz. anyway I would like to know if the parameter "Length of Parallel Routes" is about my net length (size of my track from SCLK pin from ethernet module to my microcontroler) or it is its width (like 10 mils)

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Hi Didan,
The length in the case of calculating crosstalk is the length of the track that it is in parallel with another track. The calculator looks at the crosstalk or noise that could potentially be coupled into your track, which in this case is your SPICLK, which we want clean.In your capture of your layout, this would relate to the two tracks you have going to GPIO13 and GPIO14.
-Mike

Hi, thanks for reply. What you are talking about is parameter "s" ? I would like to know "L" parameter, length of parallel route. About "s" its 0.5mm as I measured it.

s is the distance between the two tracks.
L is what I am talking about. It is the length of the track where the two signals are parallel to each other. This is different to the length of the net. 
Why are you worried about cross talk? Are there other signals (clocks or orherwise) that you are worried about interfering with? The length of the net is important for impedance matching and minimising propagation delay. Ideally clk, mosi and miso tracks should be the same length, kept away from other noisy signals and not too long. Even better if you can route them all beside each other, coupling them together. 

Looking for screenshots can you help me to determine lenth of the track? I didnt understand how to get it, yet. 

Check out the this article on EDN: https://www.edn.com/electronics-blogs/bakers-best/4426162/PCB-signal-coupling-can-be-a-problemCypress have a decent PDF on SPI Layout guidelines here with some nice diagrams: https://www.cypress.com/file/196526/download

Hello Mike. I knew about EDN article but not Cypress. Anyway, thanks for links. By the way about my question for  parameter"length"  what is this number? What screen do you need to help me with this? Its not total net length.

Hi Didan,Taking your screenshot you submitted previously, I've highlighted two different examples of parallel length tracks. The distances between each track are different, so the crosstalk will be worse as this distance between the parallel tracks decreases. Taking the red highlighted area, you need to measure the length of the tracks when they are this far apart. Looking at the blue highlighted area, you measure the length of the nets when they have this amount of seperation between them.Then take your worst case value and that's your crosstalk value.

From blue mark distance, I got 0.5mm, my trace spacing "S" parameter. I wanna to know what value to input from eeweb crosstalk calculator (https://www.eeweb.com/tools/microstrip-crosstalk) for "L" parameter, so if I understood you, S is 0.5mm (blue marks) as I measured before and L is the fartherst distance between tracks? Dont make sense it to me but its right? 

Didan,"L" is not the distance between the tracks. "S" is the distance between the tracks.I've drawn the diagram more explicitly here. To measure the Crosstalk, you have to split up the track into multiple pieces depending on the distance between the tracks. In the diagram, we have the red and blue area. Red S and Blue S are different distances, so we will have different crosstalk values, hence the split areas. The closer each track is, the worse the crosstalk will be.Notice where I've marked Red L. This is the length of the track, where Red S is the same distance between the tracks. At a rough guess, Red S is about 0.7mm apart, red L looks about 25mm in length. L is the length of the net, where the distance between the tracks in question are equal. Sometimes this is the total length of the net if the distance between the two tracks is the same for entire length of the track.Does this make sense now?

Just to clarify, you will have to calculate your Crosstalk values separately.First for the area in red, second for the area in blue.