 This is just a quick follow up to the previous video. One alert commenter had reminded me that I did not actually check the so-called AC termination or RC termination. So what I've done here is I've used a zero ohm resistor over here and on the ends I put a 100 ohm resistor with a capacitor. Now the capacitor value that I used I think it's about 160 picofarads and the reason that I did that is the rule of thumb is you take the total length of your transmission line and you double it so that's 90 centimeters and 60 centimeters is 150 centimeters and you double it so that's 300 centimeters and then you convert that to time so 300 centimeters divided by 18 is something like 16.6 or so nanoseconds and what you do is you make that your time constant. So with a 100 ohm resistor which I use because of course we've got a 100 ohm transmission line that works out to be something like 166 or so picofarads. So I chose 160 picofarads that was the closest I had and now we can take a look at the signal first at the long end and this is at 20 megahertz you can see that the waveform is actually really good. The dips aren't too low the highs are not too high in fact it goes up to 3.3 volts because remember that when we go from 0 to 3.3 the capacitor effectively looks like a short and then of course as it charges up the capacitor looks more and more like an open circuit until finally it's fully charged and it is effectively an open circuit. So the voltage is going to rise to its maximum value. So that is actually a pretty good looking waveform. The thing that is important to note is the time delay and this is one of the reasons why you may not consider an AC termination is that it does tend to stretch things out of it. Here we have an 11.44 nanoseconds delay between the low and the high but in fact maybe if I go from the low to the threshold which is 2 volts or so it's actually only 2.3 nanoseconds so in fact there's not much of a delay at all. And if I look at the other end, so we go from 3.3 volts down to 0.8 volts is the threshold so let's get to about 0.8 volts or so okay well we're almost at 2 nanoseconds so in fact this is a pretty good termination. Let's take a look at the short end now and the short end looks pretty much identical. So this is actually a really good termination I think. So thank you very much to the commenter who suggested that. The next thing to try is to see what happens on the end. Again I've chosen the capacitor so that it is for a 150 centimeter transmission line by cutting this trace I'm only going to get a 90 centimeter transmission line so the time constant is going to be basically you know something like I don't know three or four times the length which is okay. Let's go and cut this trace and see what happens. So I have cut the trace right over there maybe you can see it and let's take a look at what is going on and that still looks pretty good. So we've got again the timing looks really quite nice and everything looks pretty good. So this is a very viable termination and I think in fact that is what I'm going to use for my RISC-5 processor. Now the advantage of that is that I don't actually have to change the design of my RISC-5 registers because right now the RISC-5 registers just have the chips outputting to the bus with no source resistance. So that means that all I have to do is put the RC termination on the ends of the bus and hopefully everything should work out just fine. So I guess the next thing that I should try is to make a few more registers and make a backplane for it and see what happens. So I'll see you on that video. Take care. And I can't sing!