What is fpga code

This list is omitted here and would be pointless on a top-level module since the parameters are passed in by the parent module instantiating it. The term instantiation is used to refer to when a module or other resource is added to your design.

It means that an instance of that module or other resource is created. When you write code, each time you call a function the exact same instructions are used over and over again no matter how many times the function is called.

However, every time you instantiate a module, the entire circuit that composes the module is duplicated. If you want to reuse the same resources for multiple tasks, it is your job as the designer to figure out how you are going to juggle that.

Speaking of instantiation, typically you instantiate everything your module needs right after the port declaration.

You should think of them as wires. A wire can have a value, but it is really just a connection from one point to another. Instantiating this module is what the next couple of lines do.

To instantiate anything, you simply use the name of the resource followed by the name of this particular instance. The block that this instantiation is wrapped in is called a connection block.

This block allows you to connect an input or parameter with a given name of many modules to the same signal. In our case, we are connecting the input clk to the signal clk which is an input to our module. The syntax is. Almost every module will have a clk input and often they will have a rst input for a reset. Exactly what a clock and reset are used for will be covered later.

You can also nest the blocks and since not every block that uses clk uses rst - usually you will see something of the following form in the beginning of a module. Always blocks are where you describe all the logic that happens in your module. They contain something known as combinational logic. Combinational logic is any digital circuit whose output is a function solely of the current inputs.

They have no internal state or memory. A good example of this is an addition circuit. The output is solely determined by the two numbers currently being input. The output is always a function of the current inputs.

Inside the always block we write statements. The statements are composed of four main types. Assignments , if statements , case statements , and for loops.

Assignments are by far the most common. You have some signal on the left followed by an equals sign and then an expression. The power of these comes from the expression. Here you can use a handful of different operators to manipulate bits.

This is because division is too complicated for the tools to have a reasonable default to drop in for you. Division is still possible, it just requires a bit more effort and planning.

If the expression following the if is true non-zero then the first set of lines are valid. If it is false zero the lines in the else block are valid. The else portion is optional. Notice I said valid and not executed. It can be easy to fall into the trap when you have if statements and for loops to get in the programming mindset.

If statements are most often realized in hardware with a multiplexer. You are simply selecting one of two inputs based on some expression. When you assign a signal a value in an always block, no matter what the conditions are, it must be assigned a value. This usually means that if you assign a value to something in an if statement you should have a matching assignment in the else portion of the statement.

Another way to ensure you always assign a value is to begin your always block with some reasonable default values. Take a look at the following pseudo-code:. However, what happens when the button is pressed? Does led get assigned a value of 0 then updated with a value of 1?

When the button is pressed, led always has a value of 1. Assignments lower in an always block take precedence over previous assignments. They are simply like wires connecting two things together. These work exactly the same as if statements but are just a simpler way to have many branches on a single expression.

The value part of the case statement needs to be some constant. The optional default branch is a catch all. They are solely for code clarity and convenience. Finally we get to for loops. For loops in Lucid share the syntax to C or Java for loops but have some restrictions:. The big restriction on for loops in hardware is that they must have a constant number of iterations.

This is because the tools need to be able to unroll the loop. A for loop is no different than copy pasting that section of code over and over again except it is much easier to read. You should typically avoid them unless you have a good reason to use one.

It is very easy to create a very large and slow circuit using for loops. In Lucid, there are a handful of ways to define a numeric constant. The easiest way is to simply type the number like When you see a lone number, it is in decimal radix of 10 and the number of bits used to represent it are the minimum required in an unsigned format, unless it is negative.

If you want more control over the number of bits used, you can prefix the number with xd where x is the number of bits to be used. For example, 8d14 is the decimal value 14 represented with 8 bits. You can trade out the d for h to use hexadecimal radix of 16 , or b for binary radix of 2. With both of these formats you can specify the number of bits to use before the letter.

If you omit the number of bits, hexadecimal numbers default to using 4 bits per digit. For example, h08 uses 8 bits since I wrote two digits even though the value 8 could be represented with only 4 bits.

For binary, the number of bits is simply the number of digits when not explicitly specified. So, b is six bits wide. If a decimal number is written with the d but the number of bits omitted, it behaves the same as if the d was omitted as well.

Many signals you will encounter will be multi-bit signals like the led input in our top-level module. Bits in an array can be individually indexed using the syntax signal[bit] where bit is some expression. It is your job to ensure that the value will always fall within the bounds of the array if it is a dynamic value.

You can also access subsets of the bits using the array syntax [max:min]. Here the range of bits starting at min and going to max , inclusive, are selected. When using this syntax, both values need to be constants. Here start is the lowest bit to be selected and width is the number of bits to select above it including the start bit. With this syntax, only width needs to be constant. You can also use the slight variation [start-:width]. With this syntax, start is the highest bit in the selection instead of the lowest.

Arrays in Lucid can be multi-dimensional. When declaring them you simply tack on some extra dimensions like this:. After FPGA programming, you can run using real input or test input. The first few tries often involve figuring out why it does not work and how to fix it. Most of the time this is due to problems in the design step that were not identified in the verification step.

You will need to adapt your algorithms to add hardware architecture to process a continuous stream of data, typically with fixed-point data types. Simulink offers a time-based visual environment for hardware architecture design. A best practice is to simulate this version of your design and compare the results with your golden algorithm results.

Code generation. Synthesis and implementation. Be sure to test as many scenarios and corner cases as you can before FPGA programming because debugging on the FPGA provides far less visibility and requires longer iterations. Select a Web Site Choose a web site to get translated content where available and see local events and offers. To solve this problem, the requested algorithm needs to be implemented in FPGA using combinational or sequential logic to ensure a response time that is always the same and under milliseconds.

Such a real-time system implemented in FPGA can be modified and moved into manufacturing once it is ready. An integrated circuit created in this way will be much faster and more energy-efficient. Apart from that, FPGAs are used in projects where hardware configuration is subject to change and a circuit that can be adjusted to these changes is called for.

In case you change your hardware suppliers and the new hardware does not have the required interface, FPGA becomes a natural choice. FPGA programming consists in creating hardware architecture that will execute a requested algorithm and describe it in a hardware description language HDL. Consequently, the building blocks of this algorithm will not be a memory register and a set of operations to be performed, as with standard programs executed by CPUs or GPUs.

This offers you a great deal of flexibility. For example, if you have a bit data type, you can use exactly bit instructions to perform operations. In FPGAs, on the other hand, you can adjust to the data type because you are designing hardware architecture yourself.

You can also implement operations which are either very complex or time-consuming for general-purpose CPUs. In general-purpose CPUs, the architecture, memory and instructions are set and sealed by the manufacturer. You need to adjust to what you already have, as these elements cannot be modified. Verilog, however, is similar to C, which should make it more intuitive and easy to use for people who have no prior experience with low-level programming.

VHDL is a somewhat archaic language with certain pitfalls, one being that checking if the architecture works as expected is very hard. In some projects, to make our life easier, Python is used to generate parts of the code.

The HDL simulator is the key tool for building hardware architecture. It allows you to run the simulation of how the architecture works when given sample input data.

This in turn enables you to see how the data flows. The HDL simulator is also crucial because the process of compiling a given hardware description into an FPGA board and programming the board itself, can be very time-consuming, even for a simple program.

The simulator allows you to thoroughly verify the algorithm you want to implement into an FPGA board. Consider the cumbersome task of debugging hardware architecture. When designing such an architecture, you need to make it debuggable.

It may happen that hardware architecture in the configuration ready to be launched can be implemented on an FPGA board, but in the configuration for debugging it cannot. Such an architecture will have worse time characteristics.

Therefore, before implementing any algorithm into an FPGA board, run simulations to check whether it works as expected or not. Hardware acceleration is a main FPGA use case. In a nutshell, repetitive and compute-intensive tasks are offloaded from a computer or a server to dedicated hardware such as FPGAs. Tasks that usually fall to CPUs are offloaded to hardware.

Enabling display graphics, Graphic Processing Units GPUs are the most popular and widely used hardware for this type of operation.