WEBVTT 00:00.520 --> 00:01.320 Hi everyone. 00:01.400 --> 00:02.960 Welcome to Steam Academy. 00:03.000 --> 00:03.960 My name is Avril. 00:04.080 --> 00:09.520 In the previous video we talked about what is an AI diagram and how to construct it by superposition 00:09.520 --> 00:12.600 of bits on a polar channel. 00:13.160 --> 00:16.600 We have seen a couple of simulations as well on Security Topology Explorer. 00:17.280 --> 00:22.600 In this video we will focus on what is an eye mask and how to create an eye mask using the datasheet 00:22.640 --> 00:24.680 of Driver and Receiver ICS. 00:25.160 --> 00:30.720 We will also discuss couple of demos to see how to apply it on security Sci viewer. 00:30.920 --> 00:32.160 So let's get started. 00:36.840 --> 00:43.720 There are so many signaling schemes and interfaces we use to send or receive data, either on single 00:43.720 --> 00:45.120 ended or differential signals. 00:45.200 --> 00:49.560 For example, DTR, HDMI, PCI, EDP, etc.. 00:49.600 --> 00:56.520 Now to evaluate signal quality or to confirm that signal meets specific standards, we use a method 00:56.520 --> 00:57.600 called eye mask. 00:57.880 --> 01:04.470 It can be either diamond shape, rectangular or hexagonal, which we can create using sampling time 01:04.550 --> 01:06.190 or setup and hold time. 01:06.470 --> 01:08.950 Minimum input high voltage or maximum input. 01:08.990 --> 01:11.430 Low voltage jitter or distortion. 01:11.510 --> 01:19.070 Accepted skew parameters given on the manufacturer's document, and we apply this eye mask on eye diagram 01:19.070 --> 01:21.310 created using real world scenarios. 01:21.950 --> 01:26.630 Based on that, we got to know the violations on eye pattern and we try to resolve those. 01:31.670 --> 01:36.390 Now let's talk about different information or calculation we need to do to create eye mask. 01:36.670 --> 01:42.750 As you can see in the image we need to find out these values from A to H to create an eye mask. 01:43.350 --> 01:49.870 And very first condition is this complete eye mask should be within one UI or one unit interval. 01:49.950 --> 01:56.510 So in case of single ended signals, or in case of SDR, it should be equal to one clock period. 01:56.670 --> 02:02.110 But in case of DDR it should be either equal to one data period or one strobe period. 02:03.310 --> 02:07.330 Alright, so let me explain these measurements to you in more detail. 02:07.450 --> 02:10.130 Then we will go for the demonstration part on security. 02:10.170 --> 02:16.290 ASI viewer first point that we should remember during calculation or noting down values from manufacturer's 02:16.290 --> 02:23.690 datasheet and that is all measurements apply on eye mask are with respect to center of eye. 02:23.730 --> 02:31.170 For example, if A is equal to 2.5 nanoseconds, then this point will be 2.5 nanoseconds away from the 02:31.170 --> 02:32.530 center of eye mask. 02:32.650 --> 02:34.170 As you can see on the screen. 02:39.010 --> 02:42.090 Now we are good to go for all the formulas and measurement. 02:42.530 --> 02:45.290 So first one is h is equal to t clock. 02:45.690 --> 02:52.970 Or we can say t data period which will be equal to one unit interval where t clock is clock period in 02:52.970 --> 02:53.570 this case. 02:54.290 --> 02:58.650 Second one is O is equal to t clock by two plus t square. 02:59.050 --> 03:03.690 Now this is very useful information here skew is skew between two buses. 03:04.370 --> 03:10.720 Third point calculation can be done using OB is equal to rise time plus t setup plus t squared. 03:11.000 --> 03:15.240 And here t setup is setup time that you will get with respect to clock. 03:15.920 --> 03:22.600 Now fourth point which is OC is equal to OD is equal to t setup plus t by two plus t squared. 03:22.760 --> 03:26.880 Here T is timing jitter that will get from the datasheet. 03:27.400 --> 03:30.640 All right so this was left half of I mask. 03:31.040 --> 03:34.120 Now we have to calculate right half point of I mask. 03:34.800 --> 03:40.960 So first point is O is equal to O f is equal to t plus t jitter minus t skew. 03:41.160 --> 03:46.000 Now from these formulas we got to know that we are adjusting or shifting. 03:46.040 --> 03:52.320 I mask toward left side because on the left side we have added t skew, and on the right side we are 03:52.360 --> 03:53.720 subtracting t skew. 03:54.400 --> 03:59.080 So it is just to compensate time difference between I mask and I. 03:59.120 --> 04:01.080 Alright, let's move to another point. 04:01.120 --> 04:05.600 Next point is OG is equal to t hold plus four time minus t skew. 04:06.600 --> 04:07.080 Now here. 04:07.080 --> 04:08.440 The point is why I have. 04:08.480 --> 04:14.710 I have not considered t jitter because in most of the cases Is when we create an eye mask. 04:15.190 --> 04:18.070 We consider it as an ideal eye diagram. 04:18.390 --> 04:18.950 All right. 04:19.110 --> 04:23.870 And in that case, we are considering that t is almost equal to zero. 04:24.590 --> 04:29.950 But if it is mentioned on the data sheet the acceptable t jitter we have to add it here as well. 04:30.510 --> 04:35.990 And last point will be O which will be t minus t clock by two plus q. 04:36.150 --> 04:40.310 So it is nothing just the subtraction of left part of the eye mask. 04:40.670 --> 04:47.270 So using this equation we will get all the points on eye mask and apply them on eye diagram to validate 04:47.270 --> 04:49.910 the pattern and find out violations. 04:50.670 --> 04:55.790 Now before moving to the demonstration part here, I will conclude we need to get these values to create 04:55.790 --> 04:59.390 an eye mask from manufacturer, datasheet or other documents. 04:59.830 --> 05:06.830 And first one is clock rise time and fall time T jitter and setup and hold time. 05:06.830 --> 05:09.830 If we have these six values we can able to create eye mask. 05:10.550 --> 05:16.060 Apart from these timing information we also need some voltage information from manufacturer's Data sheet. 05:16.420 --> 05:20.020 And that is output high voltage and output low voltage. 05:20.140 --> 05:24.980 We also represent these voltages with vo min and vol max. 05:26.940 --> 05:33.620 So in case of our topology which is a synchronized LVDS signal of 400mbps. 05:38.380 --> 05:42.300 We have noted down all these values from the manufacturer's data sheet. 05:42.740 --> 05:48.020 So in our case t clock will be one upon 400 Mbps, which will be 2.5 nanoseconds. 05:48.300 --> 05:49.260 Set up and hold time. 05:49.260 --> 05:49.780 Rise time. 05:49.780 --> 05:50.420 Fall time. 05:50.500 --> 05:51.900 Skew and jitter. 05:51.940 --> 05:56.580 As mentioned on the data sheet, we are considering it almost negligible or zero. 05:57.380 --> 06:03.860 The voltage values that we should note down from the data sheet is V common, which is 1.2V for LVDS 06:04.060 --> 06:13.260 because we are following Ansi standard vo min is V common mode plus 100 volt and vol is V common mode 06:13.260 --> 06:14.580 -100 Millivolt. 06:15.300 --> 06:20.920 Now when we apply these values on the formulas that we have discussed on previous slide. 06:22.160 --> 06:24.600 We got all these points from A to H. 06:24.960 --> 06:30.400 And in the next step we are going to put these values on security topology explorers. 06:30.440 --> 06:34.320 C viewer and implement I mask over I diagram. 06:34.520 --> 06:35.520 So let's do that. 06:36.560 --> 06:41.720 So let's open Topology Explorer and run the transient analysis and plot for I diagram. 06:42.920 --> 06:46.840 Once the I diagram is there now we have to define the I mask. 06:46.880 --> 06:51.080 To do that you have to click over mask and click on define button. 06:51.320 --> 06:52.880 Let's delete this previous one. 06:53.680 --> 06:55.600 And we are going to create a new mask. 06:55.960 --> 06:59.480 Let's name it LVDS Synchronized channel. 07:00.560 --> 07:02.400 And this will be a hexagonal mask. 07:02.400 --> 07:04.960 Similarly you can plot for rectangular and diamond. 07:05.680 --> 07:10.720 Now for hexagonal mask we have to put all these values that we have created in previous step. 07:11.440 --> 07:18.920 So this will be point B, point C and point D, point E and point f and point g. 07:19.440 --> 07:23.390 So we have to add all these values with respect to this center. 07:23.910 --> 07:24.510 All right. 07:24.510 --> 07:26.510 So let's put those values quickly. 07:29.950 --> 07:35.070 So as you can see we have added all the time and voltages values for common mode voltage. 07:35.150 --> 07:39.790 We have added 1.2V which is swinging around plus -100 millivolt. 07:40.310 --> 07:45.430 So in the next step I'm just going to save this mask and click on okay. 07:46.190 --> 07:48.910 So as you can see we have applied the eye mask here. 07:49.750 --> 07:54.910 And here we can clearly see the violation of eye mask on the receiver waveform. 07:55.910 --> 08:00.950 So this is happening because the driver waveform is also not that much clean because we are operating 08:00.950 --> 08:02.510 at maximum data rate. 08:02.990 --> 08:05.190 So I will attach this project in the description. 08:05.190 --> 08:06.910 You can download it from that link. 08:06.910 --> 08:12.270 And I would suggest just play along with the driver specification, change the data rate, play with 08:12.270 --> 08:17.070 the termination resistors and try to minimize this violation. 08:18.110 --> 08:23.790 So that's it about eye mask and how to implement it on security Topology explorer and C viewer. 08:24.270 --> 08:25.470 See you in the next video.