Hello and welcome to this lecture. It's a short and simple lecture, where I want to make an important point on first match. So just to recap, first match is basically an operator or a function that stops evaluating the property at the first match of a given sequence just like shown here, the sequence may continue, but as soon as the first match is found, the Property Valuation will add. Now in this example, I want to make a point. So here's I'm setting up property B says if D is true, then starting the same clock, FMS should hold and FMS says that at the first match of ABC or E, F, E should go higher than x cloud and B C or e f is temporal domain sequence where BNC should arrive from two to five blocks, or E and F should arrive from two to five cross.
So let's look at the simulation law. In this log D is high and as required, B and C arrive two clocks later, and then a goes high. So the property passes. But note that B and C went high at 35. And then they were high even at 45. But the proper they did not continue to evaluate.
After the first B and C equal to one, it stopped right there and look for a call to one. Let's look at this example. Now he D is equal to one and then the very next clock E and F are high, but this is not according to the property because E and F should be high two clocks later. So, the first match does not succeed here, but then two clocks later B and C are high. So, the property continues at the first match and then A is high so the property passes. Now in this case D is high and two clouds letter E and F are high and it the property looks for equal to zero the next call.
Now note that on the first match of E and F property started evaluating a equal to one but the very next clock B and C were high and property did not care for it. So, the first match works as advertised. So, Let's look at one more real life application and this is on PCI bus which is a parallel bus. And what we are saying is whenever a frame is asserted meaning going low, FMS should hold. And FMS says that on the first match of bus idle buses being idle, that the next stage should go into bus idle your state machine should transition to bus idle and bus idle check is a temporal domain sequence where basically we are saying wait from two to forever until frame and I already are Hi. Now in this example, and in the previous example, if you notice first matches on the antecedent side here and and here, they are on the antecedent side and there Alright, I want to make the first match makes most sense for us on the antecedent side.
Why? Because on the consequent side, by default, the property stops evaluating on the first match of a certain given sequence. So for example, if you look at this property, where I'm saying, if A is true, then B should be true from within one to five crocs. I can also write it as if A is true on the first match of B from within one to five crocs. But as you know, in this case, the property will stop evaluating as soon as a finds B to be true. We can be true after just one talk and property will say okay, the property passes and it will not continue to evaluate any further.
So this is See the default behavior on the consequent side. So that's why this property is the same as if you were using first match. But on the antecedent side, there is no such thing. There, the antecedent side can be true, every claw, and property will continue to evaluate every call. But what we are saying as in this example, that the first time the antecedent is true, from two clauses to forever, that stop evaluating the property and then fire the consequent. So it makes most sense to us first match on the antecedent side, as opposed to using it and the consequent side.
That's all I just wanted to make this point. So that you can use first met very effectively and thank you