WEBVTT 00:00.210 --> 00:06.540 We already covered phenomenal software design flaw, so now we already know that if you have, you still 00:06.540 --> 00:09.810 could have you convert that into the big fight. 00:09.810 --> 00:12.180 Great that could be programmed on an FPGA. 00:12.600 --> 00:18.390 Now the next important concept before we actually proceed to discuss the more looks delays to understand 00:18.720 --> 00:25.590 where are the situation where signal and variable attributes look right, so we will be frequently utilizing 00:25.590 --> 00:27.000 them in and still blocks. 00:27.000 --> 00:32.490 We will try to understand now what are the uses that we have for a signal like variable rate? 00:32.880 --> 00:38.190 So first, let me just proceed with the situation right to let you know. 00:38.640 --> 00:41.550 You are building a counter right? 00:41.910 --> 00:43.920 So you are building a counter. 00:43.920 --> 00:49.050 So when we see that you are building a counter and let us assume that y use of a lever. 00:49.110 --> 00:54.060 OK, that will give us the output value of the counter right. 00:54.390 --> 01:00.330 So if our previous value acquired Zettl in the next block, it should be y equal to one. 01:00.380 --> 01:03.090 Similarly, in the next block, it should be like. 01:03.630 --> 01:03.930 Right? 01:04.350 --> 01:10.650 So if you are listening to logic, you would clearly see that to build a counter correctly, we must 01:10.650 --> 01:13.220 have an access to the previous value, right? 01:13.740 --> 01:19.670 This makes sense because once we know a previous value and the step says we have for a counter, OK, 01:20.010 --> 01:22.560 then we could predict what should be the next value, right? 01:22.570 --> 01:26.910 So in this case, if my previous value OK, so previous value is zero. 01:27.090 --> 01:33.870 And I know that the step says that I have or my count, there is way so I could see that the next two 01:33.870 --> 01:34.230 Alu. 01:34.440 --> 01:38.330 OK, next to value is zero plus one, right? 01:38.340 --> 01:39.240 So it should be what? 01:40.220 --> 01:46.520 So these are the leaders that we have for building account write letters, as you know, we declared 01:46.520 --> 01:46.790 when. 01:47.790 --> 01:52.860 Moderate, so we have to input greatly is an. 01:54.140 --> 02:01.100 So, ladies, it's you that we start building a counter, right, so why is it OK, which represent 02:01.170 --> 02:02.510 the output of account? 02:02.600 --> 02:02.870 Right? 02:03.020 --> 02:08.570 So it is having the directioners out and let us assume that our counter is off size. 02:08.780 --> 02:14.360 But so our standard and the school logic are in this corrective, OK and forward. 02:14.510 --> 02:22.940 So three down to see right now the difficulty with that out is so let's assume you want to join the 02:22.940 --> 02:23.580 logic, right? 02:23.600 --> 02:27.920 So the logic will be something like this, like let's do y plus one, right? 02:27.950 --> 02:28.550 This makes sense. 02:28.550 --> 02:33.770 So this will be odd logic depending on the algorithm that we discuss over here, right? 02:34.010 --> 02:41.390 So like lost weight +1, and this suggests that we want to use VI on in origins of our expression. 02:41.390 --> 02:47.720 But the difficulty with the output code is we could use them only on a little site, right? 02:47.720 --> 02:53.720 So they are allowed to use on an alleged site and we are not allowed to use them on an audit, just 02:53.720 --> 02:54.020 say. 02:54.050 --> 02:54.320 Right. 02:55.100 --> 03:01.280 So if you just try to implement this equation in any deal, you'll be getting an edit because output 03:01.280 --> 03:07.880 boards are not allowed to use on in order to say, OK, so this restrict us from building the counter 03:07.880 --> 03:08.660 like this, right? 03:08.870 --> 03:14.000 OK, so whenever you have a situation where you want to reuse certain value. 03:14.390 --> 03:23.840 OK, in that case, we actually the use of one of these variable type rate so you could use signal or 03:23.840 --> 03:24.680 you can use. 03:25.670 --> 03:30.040 Variable rate, so these are the new identities that we have, Rachel. 03:30.230 --> 03:36.920 The difficulty that we face with an input and output put for using the value of an output pool could 03:36.920 --> 03:39.880 be eliminated with the help of a signal of variable rate. 03:39.890 --> 03:42.470 So how are implementation of this variable? 03:42.770 --> 03:45.340 So as you when we apply, reset. 03:45.420 --> 03:51.470 OK, so when reset is high in that case, what we're going to do is that it's assumed that we declared 03:51.470 --> 03:54.140 one variable, which is of type signal. 03:54.920 --> 03:56.690 And this is the temporary variable. 03:56.690 --> 03:58.970 So we'll just be making temp equals zero. 03:59.030 --> 04:04.780 Right now, that restriction that we have with the output code, that is we cannot place it on, then 04:04.790 --> 04:08.870 origins of the expression OK is not. 04:10.420 --> 04:16.240 Not a value for the signal, right, so we could use them on, and I would just say so we could just 04:16.240 --> 04:20.080 implement an expression like this and pick words to them. 04:20.380 --> 04:25.570 Plus what right now we could take the previous value we could incrementing. 04:25.780 --> 04:31.060 So here we have our step sites and this replacing our previous one. 04:31.330 --> 04:34.650 So this exactly represent the behavior of our founder. 04:34.990 --> 04:43.210 And then at the last, when we complete our own them, we could just use the assignment operator and 04:43.210 --> 04:46.300 then connect temporary variable to an output. 04:46.780 --> 04:53.080 So whatever value that we have or temporary variable or a signal like that, property will be automatically 04:53.080 --> 04:54.040 send on an output. 04:54.640 --> 04:58.180 And this we will be able to get our counter implemented, right? 04:58.510 --> 05:01.180 So this is the first use that we have for a signal, right? 05:01.180 --> 05:04.780 So we are just understanding what are the different situation where we have. 05:05.700 --> 05:10.000 A requirement for a signal and variable and then will understand how to use them. 05:10.030 --> 05:10.250 Right? 05:11.400 --> 05:16.020 Now, you could see that same process could also be implemented with a variable rate. 05:16.230 --> 05:20.120 So whatever you can do with the signal can be done with the variable. 05:20.130 --> 05:21.930 So what is the difference that we have, right? 05:21.970 --> 05:25.530 So to understand that difference, let's consider a simple. 05:26.810 --> 05:30.050 Sequel bait, so you have a function, OK? 05:30.900 --> 05:32.730 They just need this as a unique. 05:33.670 --> 05:37.540 And then you have certain logic mentioned inside this, right? 05:37.890 --> 05:39.580 Then we have one more function. 05:40.610 --> 05:40.940 OK. 05:41.310 --> 05:43.460 And let me just name this as. 05:44.510 --> 05:45.390 X y z. 05:46.460 --> 05:48.500 OK, and then you have a logic, right? 05:48.680 --> 05:54.050 And finally, you have mean again, then you have a logic, right? 05:55.080 --> 05:56.370 So this is the sequel, right? 05:56.430 --> 06:02.340 And here in the function ABC, we have one individual variable that it just named this a z. 06:03.150 --> 06:06.300 And here we have an integer variable X. 06:06.540 --> 06:13.950 And outside of this to function, they just it's you that you have one variable which is declared outside 06:13.950 --> 06:15.000 of this to function. 06:15.210 --> 06:15.780 So when? 06:16.890 --> 06:26.070 But right now, you really see that and they have a local school that is it is visible inside this function. 06:26.550 --> 06:26.880 Right? 06:27.180 --> 06:33.860 Whereas if you consider any so it is not restricted to any of a function, you could utilize it in an 06:33.870 --> 06:35.380 EBC function. 06:35.450 --> 06:37.650 OK, you will utilize in a function next visit. 06:37.650 --> 06:40.050 Or you could also utilize in a mean function, right? 06:40.320 --> 06:46.200 So R and B is referred to as a global variable. 06:47.320 --> 06:48.890 They have a global scope. 06:49.100 --> 06:52.070 All the function can access it, right, similarly. 06:52.280 --> 06:55.670 The mean function could also access it, but when we considered in. 06:56.600 --> 07:00.230 So it is local to this function, so this is a local variable. 07:01.110 --> 07:01.370 OK. 07:01.610 --> 07:05.880 And we can see the scope of this variable is local to function EBC, right? 07:05.900 --> 07:06.480 This makes sense. 07:06.480 --> 07:10.430 So we have a score and we understand the local variable and global rating. 07:10.760 --> 07:11.090 OK. 07:11.270 --> 07:15.250 Now if you compare this with, then we still could. 07:15.390 --> 07:15.680 Right. 07:16.220 --> 07:17.440 So we have an entity. 07:18.790 --> 07:19.120 OK. 07:19.630 --> 07:26.050 And then we define all the ports which are printed in our design. 07:26.950 --> 07:27.190 Right. 07:27.520 --> 07:33.880 Then we have an architecture, OK, which represented an actual interconnection between the port and 07:33.880 --> 07:38.140 the logic that we want to implement or to have inside our system. 07:38.200 --> 07:38.470 Right. 07:39.450 --> 07:42.310 Then in between architecture and baking. 07:42.340 --> 07:47.190 Right, so we have our first big in between architecture and thinking we could declare full thing so 07:47.190 --> 07:49.220 it could be a signet, right? 07:49.260 --> 07:51.150 So signal is something that we are discussing. 07:51.450 --> 07:53.430 We could add a component over here. 07:53.840 --> 08:00.060 OK, so if you want to reuse any of the module, so the instance of that component should be declared 08:00.060 --> 08:03.220 over here, then we would have memories over here. 08:03.570 --> 08:03.840 Right? 08:03.870 --> 08:09.510 So just remember this food thing as you progress, further, things will become much easier to understand, 08:09.520 --> 08:09.750 right? 08:09.990 --> 08:11.640 We have a memory over here. 08:11.640 --> 08:16.650 And then the last thing that we could add over here is user defined. 08:17.610 --> 08:18.090 Detainee. 08:19.140 --> 08:19.400 OK. 08:19.650 --> 08:24.090 So these are the four things that we could declare between architecture and begin, right? 08:24.110 --> 08:30.150 So you see the first we in the speech that you have between architecture and begin is waiting for a 08:30.150 --> 08:32.100 declaration of this whole thing. 08:32.190 --> 08:32.410 Right. 08:32.700 --> 08:36.110 Then we have a process right off to begin. 08:36.120 --> 08:37.020 We have a process. 08:37.260 --> 08:41.520 And then again, between processes and begin, we have a space right? 08:41.760 --> 08:48.240 And this space is allocated for declaration of very human rights and something that we are discussing 08:48.240 --> 08:50.500 in this video signal and variable. 08:50.520 --> 08:55.260 So you could clearly see we have different spaces where we could declare signal. 08:55.590 --> 08:56.580 OK, and nobody. 08:56.580 --> 09:00.660 But so between architecture and begin the add signal. 09:00.810 --> 09:08.130 Similarly, between process and begin, we add very right and an architecture could have a multiple 09:08.130 --> 09:08.580 process. 09:08.760 --> 09:11.670 So this represents, let's assume, process one. 09:12.180 --> 09:12.570 OK. 09:13.320 --> 09:17.520 Similarly, we could have a process to get this again. 09:17.520 --> 09:20.580 Start with the process block and then we again have a begin. 09:20.880 --> 09:21.180 OK. 09:21.240 --> 09:25.350 Again, this piece is allocated for declaration of of you. 09:25.500 --> 09:30.280 Right now, you could clearly see the variable that you declared between the process. 09:30.370 --> 09:32.940 OK, so you have a process and then in process. 09:33.010 --> 09:33.240 Right? 09:33.570 --> 09:38.160 So they are visible between this process, right? 09:38.370 --> 09:40.050 So you could not use very well. 09:40.050 --> 09:45.570 Let's assume we declare variable V1 over here and variable v2 for the process v2. 09:45.720 --> 09:52.800 So V1 is visible only in the process, even if it is not visible to the rest of the blocks which are 09:52.800 --> 09:54.050 present in an architecture. 09:54.060 --> 09:56.310 Similarly, when we going to variable V2. 09:56.550 --> 10:00.080 So it is very it is visible only in the process, right? 10:00.300 --> 10:04.440 We could see the variable have a local school, right? 10:04.710 --> 10:07.080 So they are looking into a process. 10:08.520 --> 10:14.370 Similarly, if you consider signal, a signal are declared between architecture and begin, but they 10:14.370 --> 10:19.260 are accessible or visible to all the processes that we have in an architecture, right? 10:19.470 --> 10:24.900 So they are visible to all the blocks that are written in an architecture so they can be considered 10:24.900 --> 10:27.980 to have of global scope. 10:28.240 --> 10:31.320 So this is the primary difference that we have between them, right? 10:31.620 --> 10:37.860 So signal is visible to all the process, which you have written in an architecture whereas variable 10:38.010 --> 10:39.690 that you declared for a specific. 10:40.610 --> 10:43.100 Grosses will be visible to that process. 10:43.340 --> 10:46.340 You cannot access them outside the Barossa. 10:46.580 --> 10:49.280 So this is the fundamental difference that we have, right? 10:49.700 --> 10:56.660 So they we already know one often use off of it, either whenever you want to re-use any of the value 10:57.050 --> 10:59.900 the signal already will be choosing. 11:00.050 --> 11:06.560 And now it is purely depend on your choice, whether you want to keep that quality but local to the 11:06.560 --> 11:08.960 process or whether you want to keep that variable. 11:10.230 --> 11:15.690 To have a global scoop says that multiple prices could access it, right, the first usage, whenever 11:15.690 --> 11:23.550 you want to use any of the value, OK, you will be preparing to go it variable and the signal, right? 11:23.550 --> 11:27.860 So any one of them you would choose depending on the specific requirements that you have.