WEBVTT

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There is a universal shift register which you know file and I just want it to show you just some of

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the uses of the different keywords.

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So starting with Line 1 we have a comment just us are just kind of a better thing going on.

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And then we've got the library which you notice is highlighted in blue and I Tripoli afterwards is in

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red.

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We've got the use of Tripoli.

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Use Tripoli that gives us allows us to use standard logic vector and Arnstein and sign data types.

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And if you look we have entity generic our data with is a type of integer.

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RSA is a standard logic vector by on line 11 is a standard logic vector.

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This is also standard logic vector and reset clock our standard logic is nimbler that you can see we

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have the architecture line 17.

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We have a signal which we call a read on line 19 which is the standard logic vector data with why it

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minus one down to zero.

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So that tells us when we have a data with a we take our with is replace it with 8 8 last one to 7 down

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to zero.

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So that gives us an a register of 8 bits wide because seven down to zero is a total of eight different

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values

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and looking below that you can see we've got to begin keyword.

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We've got if rising edge is a key word as well which indicates that our clock went a toggle state.

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If it's on the rising edge then it evaluates to true if it's on the following edge.

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It does not.

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And also you look we have a case statement with a win win zero which we're taken our case of x which

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is an implied if standard logic vector to down to zero.

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So that gives us guys a three

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and you can see all the different values that have an ass when it is 0 0.

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We hold it Seirawan right shift 1 0.

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We left shift and also we have this one others which is an error code which gives us that when others

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are a register.

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We have to just do this evaluation X which is just like a undetermined value if you have a value of

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x that's just saying that you it's more or less just use for your testbench purposes and you looking

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to cast Bensons you have a value of x that just means it's undefined or uninitialized or it's an air

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value.

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Basically that because it can only be a 1 or 0 if even then X it's going to throw an error or make lines

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red.

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This makes it easier to to catch when you have errors and such is kind of a quick little overview of

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how just different keywords and what they look like in the VHDL.