Or working with the HD you know a lot of people tend to think that we're programming and actually we're
not.
So what I want to show you is here is a project I have opened Microsoft Visual Studios to see C++ project
and essentially what's going on is I have a for loop that is we have an integer I am or looping through
five times and we're just outputting the value of the variable line.
It's all going to go ahead run this is to show you what this is what type a for loop will look like
and a software type of environment.
Do the buggy build it.
Yes we do.
So we're going to build in the bug.
And as you can see our output just shows us that the value of pi changes from 0 1 2 3 4 and it's just
all happened sequentially.
So when you think of a for loop and software if you have a software background that you know it loops
through the number of times based on the parameters you give it.
It will loops through X number of times number of times and we go from zero to four which gives us five
different five times the loop through.
So if we do that VHDL How does that how is that different.
Because in VHDL they have four words.
So let's look in Xilinx.
Here is a I'm not going to go through how to create this just to show you real quick what a for loop
image will look like.
And in the syntax section we'll go ahead and cover exactly what a for loop needs to require and everything
like that.
So just looking at lines Forty-Eight in through line 50 We have a for loop where we have a variable
I am looping from 0 to 4 which is the same as the supposed possible.
We looked at and we're taking our variable A and saying it's equal to B and C..
So if we're going to have when we go ahead and synthesize this and we're going to show you the real
time logic schematic and so what that is this is just showing you the hardware that it generates.
So when you run this if you put this on an FPGA where it will look like is this right here you have
your top file one which is just a VHDL file and essentially system and gate that you have for inputs
from your C for inputs from your B just two different standard logic vectors and output.
So it's not actually sequentially going through it's just all happening simultaneous simultaneously.
You have these two inputs.
They are adding together to give you an output and so that is kind of the difference between VHDL and
software and software you're modifying the values of variables in hardware you're describing.
The fact is that you know you're describing the actual hardware.
So let's take a look and see what a VHDL hardware.
So let's say we have a digital logic circuit we want to generate in VHDL like laugh.
We have our inputs A B and C or the inputs A and B and the value of that their input C invert value
and output D and so on the right is the VHDL equivalent of that.
So if we would take the program of the right and put that into the Xilinx IAC tool and go ahead and
generate the program it would actually generate the hardware that you see on the left.
The digital logic circuit will take it in month that inside of the FPGA.
So that is what the HGL is doing we're centrally describing exactly how we want the hardware to work
we're telling it what are the inputs what are the outputs and what's going on between what are we doing
with those inputs to generate the output.