Fpga Insights

Verilog Generate: Guide to Generate Code in Verilog

Niranjana R

Updated on: January 21, 2024

Verilog Generate is a powerful feature in Verilog that allows for the creation of multiple instances of a module or conditional instantiation of any module. It provides the ability for the design to be built based on Verilog parameters, making it an essential tool for writing reusable code and increasing design efficiency.

dCdI4KKp8AjS47O3rI4KNotiybBXnLSSGvEPAIBrzCd3 ZyrL SxbbI QRH4E7GDAD3pfnZcJ4Fdae3ga88C1hw33Q6cL8HOzAUVG459wr4egxeLjTF230Xod4jyVqH9jKgAEt

Table of Contents

Understanding Verilog Generate is essential for any Verilog designer. It is a key feature that allows for the creation of complex designs with less code and increased readability. Verilog Generate can be used to create multiple instances of a module, conditionally instantiate modules, and create more flexible designs. However, it is important to be aware of the common pitfalls and solutions when using Verilog Generate, as it can be easy to make mistakes when working with it.

Key Takeaways:

  • Verilog Generate is a powerful feature that allows for the creation of multiple instances of a module or conditional instantiation of any module based on Verilog parameters.
  • Understanding Verilog Generate is essential for writing reusable code and increasing design efficiency.
  • Common pitfalls and solutions should be considered when using Verilog Generate to avoid mistakes and ensure optimal performance.

Understanding Verilog Generate

S86vRyoExsk Cg f6Tm6FRLZLOAjpb7KKeKnWZGGWPK97Wz6hqYfgvxpXw cyRtDW 0pW4wvmNd6RRAFFTBTkadVYByW2J3ACwhhXKds lvF1FPNdrmxT6doOdOs1wWv5xUDgCOpdAOKmRHzFQx VXQ

Concept and Syntax

In Verilog, generate is a powerful construct that allows for the creation of repeated instances of modules or blocks of code based on parameters and conditional statements. The generate construct is used in concurrent Verilog code blocks and is particularly useful when the same operation or module instance needs to be repeated multiple times or if certain code has to be conditionally included based on given Verilog parameters.

The syntax for generate is as follows:

The generate block can be used to create multiple instantiations of modules and code, or conditionally instantiate blocks of code. The generate block can also be used in conjunction with for, if, and case statements to create a wide variety of configurable, synthesizable RTL designs.

Usage Scenarios

There are several scenarios where the generate construct is particularly useful. One example is when creating parameterized modules. By using the generate construct in conjunction with parameters, we can create a module that can be easily customized for a variety of different use cases. For example, we can create a parameterized adder module that can add two, three, or four inputs depending on the value of a parameter.

Another scenario where the generate construct is useful is when creating a block of code that needs to be repeated multiple times. For example, we can use the generate construct to create a block of code that instantiates a series of identical flip-flops. By using a for loop within the generate block, we can easily create as many flip-flops as we need without having to manually instantiate each one.

In summary, the generate construct is a powerful tool in Verilog that allows for the creation of configurable, synthesizable RTL designs. By using parameters and conditional statements within generate blocks, we can create modules and blocks of code that can be easily customized and repeated as needed.

Verilog Generate in Hierarchical Design

AuyKP4CwAiNdlXVnGt1jHRkPXDcLJpqvjcx UHi WqDgM1sD7aMzLG2VXoegw8pWc0ltHhqZI4 yhbdP9KQn3hFj7 yIpwP4RAEGWeKNuVVU sVh 6GHWrsK5G2Jzj7KWrUJschKe1pVVikY6GC hSM

In Verilog, generate blocks are used to create hierarchical designs. They allow for the creation of multiple instances of a module or conditional instantiation of a module.

Generate Blocks

Generate blocks are used to create multiple instances of a module. They are similar to a for loop in software programming. The generate block creates a new scope and a new level of the hierarchy, similar to instantiating a module.

The syntax for a generate block is as follows:

Inside the generate block, we can use a for loop to create multiple instances of a module. For example, if we want to create four instances of a module, we can use the following code:

In this code, the for loop creates four instances of the module “module_name” with the input and output ports connected to the input and output arrays.

Generate Loops

Generate loops are used to conditionally instantiate a module. They are similar to an if statement in software programming. The generate loop creates a new scope and a new level of hierarchy, similar to instantiating a module.

The syntax for a generate loop is as follows:

Inside the generate loop, we can use an if statement to conditionally instantiate a module. For example, if we want to instantiate a module only if a condition is true, we can use the following code:

In this code, the module “module_name” is instantiated only if the “enable” signal is true.

In conclusion, generate blocks and loops are powerful tools in Verilog that allow for the creation of hierarchical designs. By using generate blocks and loops, we can create multiple instances of a module or conditionally instantiate a module, making our designs more flexible and efficient.

Advanced Techniques with Verilog Generate

aCX0bMwdGigw15vOj1aHOzknlNQxVceOas6iYIBoLMP8XgUORVeciuQ r3NeOVW1R 54NPM2GKO n7ri8vWXC mSzovl1V W 6l3FtyGW

When it comes to Verilog Generate, there are a few advanced techniques that can be used to create more complex and powerful designs. In this section, we will explore two of these techniques: Conditional Generate Constructs and Parameterized Modules.

Conditional Generate Constructs

Conditional Generate Constructs are a powerful way to create designs that can adapt to changing conditions. These constructs allow us to generate code based on a set of conditions, which can be used to create complex designs that are more efficient and flexible.

One example of a Conditional Generate Construct is the “generate if” statement. This statement allows us to generate code based on a condition, which can be used to create designs that are more efficient and flexible. Another example is the “generate case” statement, which allows us to generate code based on a set of conditions.

Parameterized Modules

Parameterized Modules are another powerful technique that can be used to create more flexible and efficient designs. These modules allow us to create designs that can be customized based on a set of parameters, which can be used to create designs that are more efficient and flexible.

One example of a Parameterized Module is a RAM module. By using parameters, we can create a RAM module that can be customized based on the size of the memory, the width of the data bus, and other factors. Another example is a FIFO module, which can be customized based on the size of the FIFO buffer, the width of the data bus, and other factors.

Overall, by using these advanced techniques with Verilog Generate, we can create more powerful and flexible designs that can adapt to changing conditions and requirements.

Common Pitfalls and Solutions

Ltef3A9GbUOtV8vuoVLLE653tuZSbYEJljUnl 3MB2Qpjj twWUhBfyn0Tuv h1N4 WQFdkf1Q3ggvJo4a8wN806AKZ91UeEDvvzos0pMMTjBy 8pm5TfgNnRYGaqqOgoSJ

Debugging Tips

Debugging Verilog code can be a challenging task, especially when it involves the use of generate statements. Here are some tips to help you debug your Verilog code more effectively:

  • Use simulation tools: Simulation tools such as ModelSim can help you simulate your Verilog code and identify any errors or issues in your design. By simulating your design, you can verify that it is functioning as intended and identify any issues that need to be addressed.
  • Use waveform viewers: Waveform viewers such as GTKWave can help you visualize the signals in your Verilog code and identify any issues with your design. By examining the waveforms, you can verify that the signals are behaving as expected and identify any issues that need to be addressed.
  • Use print statements: Print statements can be used to output the value of a signal or variable at a specific point in your Verilog code. By using print statements, you can verify that the signals and variables in your code are behaving as expected and identify any issues that need to be addressed.

Best Practices

In addition to debugging tips, there are also some best practices that you should follow when working with Verilog to generate statements. Here are some best practices to keep in mind:

  • Avoid using too many generate statements: While generating statements can be a powerful tool for creating reusable Verilog code, it is important to avoid using too many generate statements in your design. Too many generated statements can make your code difficult to read and debug, and can also slow down the synthesis process.
  • Use parameters to make your code more flexible: Parameters can be used to make your Verilog code more flexible and reusable. By using parameters, you can create parameterized modules that can be easily customized for different applications.
  • Use generate blocks to reduce duplication: Generate blocks can be used to reduce duplication in your Verilog code. By using generate blocks, you can create a single block of code that can be instantiated multiple times with different parameters.

By following these best practices and debugging tips, you can create more effective Verilog code that is easier to read, debug, and maintain.

Future of Verilog Generate

E06s4mUVhLlEoEIJC4DHTixPWHmIkhkX6SCxe68zlvCEFDhg9TLF9NEQdRlTgsGw356s7uMHeHO EmyfAQQtzzw avuFm1gYCiLzBCpGOfMTNLgoIATHq1zvpEya42cJAAmXIP6aiRHJ0Z oO9ciOU

Verilog Generate has been a popular feature in hardware design for many years. As the field of hardware design continues to evolve, Verilog Generate is expected to play an even bigger role in the future. In this section, we will discuss the future of Verilog Generate and its impact on modern design.

Updates and Trends

Verilog Generate is a mature feature, and as such, it is not expected to undergo any major changes in the future. However, there are some trends that we expect to see in the coming years. One of these trends is the increasing use of SystemVerilog, which provides more advanced features for hardware design. SystemVerilog includes enhancements to Verilog Generate, such as the ability to generate code based on interfaces and classes.

Another trend that we expect to see is the increasing use of tools that automate the generation of Verilog code. These tools can help designers quickly create complex designs that are difficult to create manually. They can also help to reduce errors and improve the overall quality of the design.

Impact on Modern Design

Verilog Generate is expected to have a significant impact on modern design. One of the biggest benefits of Verilog Generate is its ability to create reusable code. This can help to reduce design time and improve the overall quality of the design. Verilog Generate is also expected to play a key role in the development of complex designs, such as those used in artificial intelligence and machine learning.

In addition, Verilog Generate is expected to play a key role in the development of designs for the Internet of Things (IoT). As the number of connected devices continues to grow, designers will need to create designs that are highly efficient and scalable. Verilog Generate can help to achieve these goals by allowing designers to create designs that are modular and reusable.

Overall, Verilog Generate is a powerful tool that is expected to play an important role in the future of hardware design. As hardware design continues to evolve, we expect to see new trends and updates that will further enhance the capabilities of Verilog Generate.

Related Articles

LOOPS IN VERILOG A COMPREHENSIVE GUIDE

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed .

PCI Express 3.0 (1)

most recent

verilog task generate

Artificial Intelligence

Unlocking the potential of students: the role of ai in tailoring learning paths.

verilog task generate

AI in Agriculture: Precision Farming for Sustainable Food Production

verilog task generate

Test & Measurement

Testing tools for low-code and no-code development: ensuring quality in rapid development.

verilog task generate

Wireless Networking

Sustainable wireless networks: energy-efficient communication.

verilog task generate

Revolutionizing Global Communication: The Role of AI in Language Translation

verilog task generate

Women in Engineering

Purnima kumari sharma, r&d engineer: women in engineering, subscribe to get our best viral stories straight into your inbox, related posts.

  • Loops in Verilog: A Comprehensive Guide November 23, 2023
  • Unraveling Verilog Modules: An In-Depth Exploration of Verilog Module Syntax and Operations December 20, 2023
  • Unlocking the Power of Verilog While Loop: Optimizing Performance and Streamlining Design January 18, 2024
  • System Verilog Operators: A Comprehensive Guide December 3, 2023
  • Demystifying Verilog Test Benches: A Step-by-Step Example December 20, 2023
  • Testbench VHDL Example: A Clear and Concise Guide December 3, 2023

verilog task generate

FPGA Insights have a clear mission of supporting students and professionals by creating a valuable repository of FPGA-related knowledge to contribute to the growth and development of the FPGA community and empower individuals to succeed in their projects involving FPGAs FPGA Insights has been producing FPGA/Verilog/VHDL Guides and blogs with the aim of assisting students and professionals across the globe. The mission of FPGA Insights is to continually create a growing number of FPGA blogs and tutorials to aid professionals in their projects.

© 2024 Fpga Insights. All rights reserved

  • Randomization
  • Random Stability
  • String Methods
  • Convert hex, int, bin to string
  • Convert string to hex, int, bin
  • 10 Useful Utilities

SystemVerilog Generate Construct ¶

Overview ¶.

The Generate construct is a very useful tool. You'll commonly see it used for these 3 purposes

  • Lazy instantiation of module items using a for-loop
  • Changing the structure or design of a module using SystemVerilog Parameters
  • Using generate with assertions for Functional and Formal Verification

Generate Overview

Before we begin, there's one important thing to understand about the generate construct. Generate blocks are evaluated during elaboration time and the result is determined before the simulation begins. In other words generate statements are NOT a run-time construct. If you think about it for a second, the generate construct is actually creating a circuit and we cannot add or remove hardware circuits on-the-fly, so it does make sense that a generate block is evaluated during elaboration.

Loop Generate Construct ¶

The loop generate construct provides an easy and concise method to create multiple instances of module items such as module instances, assign statements, assertions, interface instances and so on. Think of it as a cloning machine.

In essence it is a special type of for loop with the loop index variable of datatype genvar . Here's an interesting fact about genvar - it is an integer datatype that exists only during elaboration time and disappears at simulation time.

You may also find the testbench for the above example useful!

Check it out here

... and as you would expect, you can nest generate for-loops. Just make sure you use separate genvars for the outer and inner loop and take care while referencing these vars in your nested for-loop. This is a common place where mistakes are made.

Get Notified when a new article is published!

Conditional Generate Construct ¶

The conditional generate construct lets you alter the structure of your design based on Parameter values passed during module instantiation. This is tremendously useful while creating parameterized common RTL blocks for your design.

A simple example -

Another example - You've been given the task of creating a common CRC generator block. Other designers in the team should be able to choose between 1 of 3 polynomials for the CRC calculation.

Here is one way to do it - you provide a parameter called CRC_SEL , which is set when this module is instantiated, and this CRC_SEL param selects which CRC function is generated within the module. By using a generate block instead of a simple mux, you save a bunch of gates and flops because the CRC functions that are not required are never instantiated.

Generate CRC Example

The code is explained within comments. An important thing to notice is how the function is called using crc_poly.CRC16_D8() . Read more about it in the code comments.

Certain parts of the code have been omitted to keep the snippet short. Download complete working version of this example

scroll to see more code

For completion, follow the github link and also take a look at the testbench code for the above crc_gen module, you may find it useful. Here are some waves from the testbench stimulus.

CRC Gen Waves

Assertions and Formal Verification ¶

The generate construct is also very useful while writing assertions and this in-turn helps with Formal Verification.

If you have any experience with Formal Verification, then you'll know that Formal tools very quickly run into computational bounds while trying to prove properties. So, it is important to keep your properties short and simple.

For example, if you have an arbiter block with 8 REQquest inputs and 8 ACK outputs, then instead of writing a single assertion to cover all 8 REQ/ACK pairs, it is better to break it down into 8 individual assertions with 1 REQ/ACK pair per assertion.

Here's another example, this is a little more exciting.

Let's say you have a Client - Server system and you have to do Formal Verification on the RTL model of the Client and that of the Server individually. The assertions on the outputs of the Client become assumptions on the input of the Server , and vice-versa. So, instead of writing separate assertions for each of them, this is how you could build your Formal TB.

  • Write a common module with all the properties. Define a parameter to tell this "properties module" if the CLIENT_IS_DUT or if SERVER_IS_DUT .
  • Bind the properties module to the Client or Server and pass the appropriate Parameter when doing the bind
  • Use a recipe of Generate and the Macro constructs to define your properties as assert or assume .

Like this -

The above example was adapted from the book Formal Verification , Erik Seligman, et al. , Chapter 7: Page 194

Hierarchically Accessing Generated Blocks ¶

One thing that trips up people is how to access a module item that are located within a generate block.

A generate block is always given a name. If you don't name it, the compiler will automatically assign a generic name such as genblk01 , genblk02 and you will typically have to dump waves and look at your Visualizer tool to see what names were assigned.

To access a module item within a generate block, you have to hierarchically access it using <generate_blk_name>.<module_item_name> . This is why in example 2.2 we invoked the CRC polynomial function by calling crc_poly.CRC16_D8() (i.e., <generate_blk_name>.<function_name> ).

Here's a nice example from the SystemVerilog LRM 1800-2012 (example 4 section 27.5). Look at how you access the task and module instance defined within the case-generate block.

In a Nutshell ¶

Wrapping things up - this is what we discussed in this article:

  • How to use loop generate construct to create multiple instances of module items
  • How to use conditional generate construct to change the module's design based on SystemVerilog parameters
  • How to use loop and conditional generate constructs with assertions
  • How to hierarchically access module items within generate blocks

References ¶

  • easics crc tool
  • Formal Verification - Erik Seligman, et al.

Questions & Comments ¶

For questions or comments on this article, please use this GitHub Discussions link .

Every month or so I send out a newsletter with lessons from my experience, notable technical papers, and notifications about new articles.

If you found this content useful then please consider supporting this site! 🫶

Buy Me A Coffee

If you would like to be notified when a new article is published, please sign up. If you found this content useful then please consider supporting this site! 🫶

Verilog Task

A function is meant to do some processing on the input and return a single value, whereas a task is more general and can calculate multiple result values and return them using output and inout type arguments. Tasks can contain simulation time consuming elements such as @ , posedge and others.

A task need not have a set of arguments in the port list, in which case it can be kept empty.

Static Task

If a task is static, then all its member variables will be shared across different invocations of the same task that has been launched to run concurrently

The task-enabling arguments (x, y, z) correspond to the arguments (a, b, c) defined by the task. Since a and b are inputs, values of x and y will be placed in a and b respectively. Because c is declared as an output and connected with z during invocation, the sum will automatically be passed to the variable z from c .

Automatic Task

The keyword automatic will make the task reentrant, otherwise it will be static by default. All items inside automatic tasks are allocated dynamically for each invocation and not shared between invocations of the same task running concurrently. Note that automatic task items cannot be accessed by hierarchical references.

For illustration, consider the static task display which is called from different initial blocks that run concurrently. In this case, the integer variable declared within the task is shared among all invocations of the task and hence thev displayed value should increment for each invocation.

If the task is made automatic, each invocation of the task is allocated a different space in simulation memory and behaves differently.

Global tasks

Tasks that are declared outside all modules are called global tasks as they have a global scope and can be called within any module.

If the task was declared within the module des , it would have to be called in reference to the module instance name.

Difference between function and task

Although Verilog functions and tasks serve similar purposes, there are a few notable differences between them.

When a function attempts to call a task or contain a time consuming statement, the compiler reports an error.

Disable Task

Tasks can be disabled using the disable keyword.

When display task was launched by the first initial block, T_DISPLAY started and got disabled when time reached 50 units. Immediately the next block S_DISPLAY started and ran to completion by 80 units.

DMCA.com Protection Status

Verilog Pro

Verilog Generate Configurable RTL Designs

Verilog generate statement is a powerful construct for writing configurable, synthesizable RTL. It can be used to create multiple instantiations of modules and code, or conditionally instantiate blocks of code. However, many Verilog programmers often have questions about how to use Verilog generate effectively. In this article, I will review the usage of three forms of Verilog generate—generate loop, if-generate, and case-generate.

Types of Verilog Generate Constructs

There are two kinds of Verilog generate constructs. Generate loop constructs allow a block of code to be instantiated multiple times, controlled by a variable index. Conditional generate constructs select at most one block of code between multiple blocks. Conditional generate constructs include if-generate and case-generate forms.

Verilog generate constructs are evaluated at elaboration, which occurs after parsing the HDL (and preprocessor), but before simulation begins. Therefore all expressions within generate constructs must be constant expressions, deterministic at elaboration time. For example, generate constructs can be affected by values from parameters, but not by dynamic variables.

A Verilog generate block creates a new scope and a new level of hierarchy, almost like instantiating a module. This sometimes causes confusion when trying to write a hierarchical reference to signals or modules within a generate block, so it is something to keep in mind.

Use of the keywords generate and endgenerate (and begin / end ) is actually optional. If they are used, then they define a generate region . Generate regions can only occur directly within a module, and they cannot nest. For readability, I like to use the generate and endgenerate keywords.

Verilog Generate Loop

The syntax for a generate loop is similar to that of a for loop statement. The loop index variable must first be declared in a genvar declaration before it can be used. The genvar is used as an integer to evaluate the generate loop during elaboration. The genvar declaration can be inside or outside the generate region, and the same loop index variable can be used in multiple generate loops, as long as the loops don’t nest.

Within each instance of the “unrolled” generate loop, an implicit localparam is created with the same name and type as the loop index variable. Its value is the “index” of the particular instance of the “unrolled” loop. This localparam can be referenced from RTL to control the generated code, and even referenced by a hierarchical reference.

Generate block in a Verilog generate loop can be named or unnamed. If it is named, then an array of generate block instances is created. Some tools warn you about unnamed generate loops, so it is good practice to always name them.

The following example shows a gray to binary code converter written using a Verilog generate loop.

Another example from the Verilog-2005 LRM illustrates how each iteration of the Verilog generate loop creates a new scope. Notice wire t1, t2, t3 are declared within the generate loop. Each loop iteration creates a new t1, t2, t3 that do not conflict, and they are used to wire one generated instance of the adder to the next. Also note the naming of the hierarchical reference to reference an instance within the generate loop.

Generate loops can also nest. Only a single generate / endgenerate is needed (or none, since it’s optional) to encompass the nested generate loops. Remember each generate loop creates a new scope. Therefore the hierarchical reference to the inner loop needs to include the label of the outer loop.

Conditional If-Generate

Conditional if-generate selects at most one generate block from a set of alternative generate blocks. Note I say at most , because it may also select none of the blocks. The condition must again be a constant expression during elaboration.

Conditional if-generate may be named or unnamed, and may or may not have begin / end . Either way, it can contain only one item. It also creates a separate scope and level of hierarchy, like a generate loop. Since conditional generate selects at most one block of code, it is legal to name the alternative blocks of code within the single if-generate with the same name . That helps to keep hierarchical reference to the code common regardless of which block of code is selected. Different generate constructs, however, must have different names.

Conditional Case-Generate

Similar to if-generate, case-generate can also be used to conditionally select one block of code from several blocks. Its usage is similar to the basic case statement , and all rules from if-generate also apply to case-generate.

Direct Nesting of Conditional Generate

There is a special case where nested conditional generate blocks that are not surrounded by begin/end can consolidate into a single scope/hierarchy. This avoids creating unnecessary scope/hierarchy within the module to complicate the hierarchical reference. This special case does not apply at all to loop generate.

The example below shows how this special rule can be used to construct complex if-else if conditional generate statements that belong to the same hierarchy.

This generate construct will select at most one of the generate blocks named u1. The hierarchical name of the gate instantiation in that block would be test.u1.g1. When nesting if-generate constructs, the else always belongs to the nearest if construct. Note the careful placement of begin / end within the code Any additional begin / end will violate the direct nesting requirements, and cause an additional hierarchy to be created.

Named vs Unnamed Generate Blocks

It is recommended to always name generate blocks to simplify hierarchical reference. Moreover, various tools often complain about anonymous generate blocks. However, if a generate block is unnamed, the LRM does describe a fixed rule for how tools shall name an anonymous generate block based on the text of the RTL code.

First, each generate construct in a scope is assigned a number, starting from 1 for the generate construct that appears first in the RTL code within that scope, and increases by 1 for each subsequent generate construct in that scope. The number is assigned to both named and unnamed generate constructs. All unnamed generate blocks will then be given the name genblk[n] where [n] is the number assigned to its enclosing generate construct.

It is apparent from the rule that RTL code changes will cause the unnamed generate construct name to change. That in turn makes it difficult to maintain hierarchical references in RTL and scripts. Therefore, it is recommended to always name generate blocks.

Verilog generate constructs are powerful ways to create configurable RTL that can have different behaviours depending on parameterization. Generate loop allows code to be instantiated multiple times, controlled by an index. Conditional generate, if-generate and case-generate, can conditionally instantiate code. The most important recommendation regarding generate constructs is to always name them, which helps simplify hierarchical references and code maintenance.

  • 1364-2005 – IEEE Standard for Verilog Hardware Description Language

Share this:

  • Click to share on LinkedIn (Opens in new window)
  • Click to share on Twitter (Opens in new window)
  • Click to share on Facebook (Opens in new window)
  • Click to share on Pocket (Opens in new window)
  • Click to email a link to a friend (Opens in new window)
  • Click to print (Opens in new window)

17 thoughts on “Verilog Generate Configurable RTL Designs”

Great article! I often use for-generate loops but I didn’t know about existing of if- and case-generate conditions 🙂

Thanks for the Posting. I recently saw a “conditional generate” code that I wasn’t aware of. Good to see this detailed explanation.

This is superb. Thanks for this great resource Jason!

Is there a way to use generate blocks for signal declarations? When I check with the systemverilog LRM I see this sentence, “A generate block may not contain port declarations, specify blocks, or specparam declarations.”.

What about internal signal declarations? For instance, if I have two different structs with different fields inside the structs, and I want to choose between the two types for an internal signal declaration type (note not a port) something like the below gives a compile error saying the signal is not declared.

parameter integer unsigned some_parameter = 1;

generate if (some_parameter == 1) begin type_a x; end else if (some_parameter = 0) begin type_b x; end endgenerate

Then at some point below X is referenced.

Thanks in advance!

Hi Sami. That’s an interesting question. I tried something similar to your code and also encountered an error during compilation that the type is unknown. I suspect it’s because generate statement is only resolved during elaboration, but the type needs to already exist during compilation. How I usually handle something like that is if the parameter only affects a field within the struct, I parameterize that field to use the parameter, rather than use generate to select between two structs. Also, you can pass a TYPE as a parameter into a module, and use that TYPE in the struct. That may also achieve what you’re looking for.

Thanks for the quick reply! Yes, what you suggested is the first approached I tried. I have parameters for the width of the fields in the struct. My hope with that approach is if the width parameter is set to 0 then that field should not exist. I wasn’t sure if that would be reality of what would happen. I noticed that in simulations that field shows up with negative index. For example:

parameter FIELD_WIDTH = 0; … logic [FIELD_WIDTH-1:0] x;

This will show up as x[-1:0] in waveforms. What I don’t know is if this is a tool quirk or this will actually synthesize to two bits.

Hi Jason, Great article. Is it possible to change the loop index inside the generate block itself? For example, in a generate block, I have an if statement which generates two instantiations and in the else statement it instantiates one. So I’d like to increment the loop index in the if statement itself. Is it possible? Regards, Kunal

Nice post. Seeing that you are using instances of logic gates. Guess I can instantiate any other module, but what about processes such as “always” or “assign”?

Yes you can also wrap always and assign statements in a generate.

Beautifully written, terse and clear!

Great article but there are several errors,

module for_loop_synthesis (i_Clock); input i_Clock; integer ii=0; reg [3:0] r_Shift_With_For = 4’h1; reg [3:0] r_Shift_Regular = 4’h1;

// Performs a shift left using a for loop always @(posedge i_Clock) begin for(ii=0; ii<3; ii=ii+1) r_Shift_With_For[ii+1] <= r_Shift_With_For[ii]; end

// Performs a shift left using regular statements always @(posedge i_Clock) begin r_Shift_Regular[1] <= r_Shift_Regular[0]; r_Shift_Regular[2] <= r_Shift_Regular[1]; r_Shift_Regular[3] <= r_Shift_Regular[2]; end endmodule

module for_loop_synthesis_tb (); // Testbench reg r_Clock = 1'b0; // Instantiate the Unit Under Test (UUT) for_loop_synthesis UUT (.i_Clock(r_Clock)); always #10 r_Clock = !r_Clock; endmodule

module gray2bin #(parameter SIZE = 8) ( input [SIZE-1:0] gray, output [SIZE-1:0] bin );

generate genvar gi; // generate and endgenerate is optional // generate (optional) for (gi=0; gi<SIZE; gi=gi+1) begin : genbit assign bin[gi] = ^gray[SIZE-1:gi]; end // endgenerate (optional) endgenerate endmodule

module gray2bin_tb(); //Testbench reg [15:0] in,out;

gray2bin #(16) DUT ( .gray(in), .bin(out) );

integer jj=0;

initial begin

for(jj=0;jj<16;jj=jj+1) begin in=jj; #5; end end

i have corrected all of them for you

thank you for making this cheers

Thanks for spotting the typo!

Nice work… Keep going…. Nice page…

Sir gray2bin code is synthesizable yes not and can I implement on the FPGA board

Yes it is certainly synthesizable and can be implemented in FPGA.

Nice article Jason, very helpful for beginners.

in the for loop,what is the meaning of the” gi=0; gi<SIZE; gi=gi+1″ .should gi < size

Leave a Comment Cancel reply

Notify me of follow-up comments by email.

Notify me of new posts by email.

This site uses Akismet to reduce spam. Learn how your comment data is processed .

GitHub

Task – Verilog Example

Write synthesizable and automatic tasks in verilog.

Tasks are sections of Verilog code that allow the Digital Designer to write more reusable, easier to read code. Tasks are very handy in testbench simulations because tasks can include timing delays . This is one of the main differences between tasks and functions , functions do not allow time delays .

Tasks should be utilized when the same operation is done over and over throughout Verilog code. Rather than rewriting code, one can just call the task. This reduces copy/paste errors in your code and allows quicker development time. It also makes the code much cleaner and easier to read. Yes, tasks can be synthesized!

Below is a list of rules for tasks:

  • Tasks can have any number of inputs and outputs
  • The order of inputs/outputs to a task dictates how it should be wired up when called
  • Tasks can have time delay (posedge, # delay, etc)
  • Tasks can call other tasks and functions
  • Tasks can drive global variables external to the task
  • Variables declared inside a task are local to that task
  • Tasks can use non-blocking and blocking assignments
  • Tasks can be automatic (see below for more detail)

Often tasks are created in the file they are used in. The example below demonstrates this. However tasks can also be included via the `include compile directive.

task_example.v:

The Modelsim simulation screenshot below shows the result of the operation of the task.

Modelsim results of Verilog task

Automatic Tasks

Tasks can be declared as automatic tasks as of Verilog 2001.

Automatic is a term borrowed from C which allows the task to be re-entrant. A re-entrant task is one in which the items declared within the task are allocated upon every individual call of the task, as opposed to being shared between all calls of the task. This could be a problem in a simulation environment if code is forked and calls the same task at the same time. Race conditions can develop.

In C, all variables are automatic by default. In order to make them not automatic, they must be declared as static . Verilog is the opposite with tasks. All tasks are static by default and should be declared automatic if they are called simultaneously. A good practice is to declare your tasks as automatic by default. The example below displays the difference between a re-entrant task and a regular task. The non-automatic task is likely not behaving the way the user intended!

Learn Verilog

Leave A Comment Cancel reply

Save my name, email, and website in this browser for the next time I comment.

generate loops in Verilog

Generate loops in verilog.

Traditional for and while loops are “behavioral” loops. Verilog also supports structural loops that create repeated instances of a submodule, or repeated assignments. This capability uses the generate syntax. As an example, we will implement a classic ripple carry adder using structural syntax.

You may be familiar with the standard full adder logic module, defined in the code below.

The ripple-carry adder is a string of full-adder modules, where the c_out (carry out) from each module connects to the c_in (carry in) of the next module. This is illustrated in the schematic figure shown below.

In Verilog, a structural model is a direct description of a schematic like the one in the figure. Some models require many repetitions of the same submodule, and it is inefficient to code each instantiation separately. The generate statement allows us to place and connect all the modules automatically. An additional benefit is that generate loops can be parameterized , so the structure is adjustable.

The code below describes an N bit ripple-carry adder with default size N= 4 .

To connect the carry chain, we declared a wire vector named c , corresponding to the blue labels in the schematic diagram. The wire signals can be directly connected to submodule ports. To connect the end-points at c_in and c_out , we use assign statements.

Assigned Tasks

In the src/ directory, create files named full_adder.v and adder.v containing the module definitions given above.

Simulate the Design

Edit the testbench template in testbench.v and make the following additions:

  • To create an exhaustive test spanning all input combinations, use the concatenation operator to make simultaneous assignments to a , b , and c_in like this:

Place this assignment in the always block labeled “CREATE STIMULI”.

  • Since a and b have four bits, and c_in has one bit, there are a total of 9 input bits. To verify all input combinations, we need to simulate 2^9 cases. The clk_count signal takes gets a unique value every clock cycle, so after 2^9 cycles we should have incremented through all the test cases. Find the termination condition in the testbench, and change it so that it stops when clk_count equals 2^9.

After making the changes, run make simulate to verify the behavior. You should see a table of outputs like this:

Notice that a , b , and s are printed as decimal values thanks to the %d option in the $write statements:

Scroll through the results and verify that the correct sum and carry are produced.

View the Hierarchy

Next open build.tcl and notice that some changes were made. The synth_design line has some extra commands that request a partial synthesis:

The options here request that Vivado perform “rtl” synthesis (not targeted to any specific FPGA chip), and preserve the design hierarchy. After synthesis, the result is written to a file called rtl-synth.v . Run make implement to perform the partial synthesis, then open the rtl-synth.v file. You should see that the generate loop is expanded into four full_adder modules that look like this:

The generate loop is assigned a default name, genblk1 . The instances within genblk1 are referenced like a vector as genblk1[ 0 ] , genblk1[ 1 ] , and so on. Within each genblk1 instance, the full_adder instances are named genblk1[ 0 ].fa , genblk1[ 1 ].fa , and so on.

Named generate blocks

When testing and debugging a design, default names like genblk1 can be mysterious and confusing. Verilog allows named generate loops. Modify the generate loop in adder.v so that it has the name myadder , like this:

Then modify the $write and $fwrite statements in testbench.v so that it prints submodule signals for myadder[ 0 ].fa . The generic format for referencing sub-module signals is submodule1.submodule2.signal_name , like this:

Repeat the make simulate and make implement actions. In the file rtl-synth.v you should notice that the generate instances are now named myadder[ 0 ].fa , myadder[ 1 ].fa , and so on.

Examine the final results in test_result.txt and verify that the submodule signals are correct.

Turn in your work using git :

Indicate on Canvas that your assignment is done.

VLSI Verify

Tasks and Functions in Verilog

A function or task is a group of statements that performs some specific action. Both of them can be called at various points to perform a certain operation. They are also used to break large code into smaller pieces to make it easier to read and debug.

Functions in Verilog

A function that does not consume simulation time, returns a single value or an expression, and may or may not take arguments.

Keywords used: function and endfunction.

Tasks in Verilog

A task that may or may not consume simulation time, returns values as output or inout argument type, and may or may not take arguments.

Keywords used: task and endtask.

Similarities between function and task

  • Both are static in nature by default. Refer to System Verilog tasks and functions for more details.
  • Both support default arguments and arguments have input direction by default unless it is specified.
  • Multiple statements can be written without using a begin .. end block.

Difference between function and task

Verilog Tutorials

An Introduction to Tasks in SystemVerilog

In this post we look at tasks and how we can use them to write SystemVerilog code which is reusable .

As we talked about in the post on SystemVerilog functions , tasks and functions are collectively known as subprograms.

We use subprograms to write small pieces of SystemVerilog code which we can use easily insert into our designs.

This allows us to reduce development time as we can easily port these small pieces of code between different designs.

There are two main differences between functions and tasks.

When we write a SystemVerilog function, it performs a calculation and returns a single value.

In contrast, a SystemVerilog task executes a number of sequential statements but doesn't return a value. Instead, the task can have an unlimited number of outputs .

In addition to this, SystemVerilog functions execute immediately and can't contain time consuming constructs such as delays, posedge macros or wait statements.

In contrast, we can use time consuming constructs inside of a SystemVerilog task.

We will discuss the use of SystemVerilog tasks in more detail in the rest of his post.

If you are already familiar with verilog then you may wish to skip most of this post. The reason for this is that SystemVerilog tasks inherit most of their behavior directly from verilog.

However, you may still wish to read the sections on returning from tasks , automatic variables and passing by reference as these features were all introduced as part of SystemVerilog.

SystemVerilog Task

Just like functions, we use tasks to implement small sections of code which we can reuse throughout our design.

In SystemVerilog, a task can have any number of inputs and can also generate any number of outputs. This is in contrast to functions which can only return at most one value.

Unlike functions, we can also use timing consuming constructs such as wait, posedge or delays (#) within a task.

As a result of this, we can use both blocking and non-blocking assignment in SystemVerilog tasks.

These features mean we typically use tasks to implement simple pieces of code which we need to repeat several times in our design. A good example of this would be driving the pins on a known interface, such as SPI or I2C .

We can write the code for a task inside a  module , class or package in SystemVerilog.

The code snippet below shows the general syntax for a task in SystemVerilog.

As with functions, there are two ways in which we can declare a task but the performance of both approaches is the same.

We must give every task a name, as denoted by the <name> field above.

When we write tasks which declare the inputs and outputs within the task body, we must use the begin and end keywords as well.

However, when we use inline declaration for the inputs and outputs, we can omit the begin and end keywords.

When we write tasks in SystemVerilog, we can also declare and use local variables. This means that we can create variables in a task which we can't access in other parts of our design.

In addition to this, we can also access all global variables within a SystemVerilog task.

Unlike SystemVerilog functions, we can call another task from within a task. We can also make calls to functions from within a task.

  • SystemVerilog Task Example

Let's consider a simple example to better demonstrate how to write a SystemVerilog task.

For this example, we will write a basic task which generates a pulse when we call it. The length of the pulse can be specified when we call the task in our design.

To do this we require one input, which determines how long the pulse is, and an output for the generated pulse.

The SystemVerilog code below shows the implementation of this example using the two different styles of task.

Although this example is trivial, we can see here how we can use the verilog delay operator (#) in a task. If we attempted to write this code in a function, this would cause an error when we tried to compile it.

We can also see from this example that we don't return a value in the same way as we do with a function.

Instead, we must declare any outputs which we use in the task declaration.

We can include and drive as many outputs as we want when we write a task in SystemVerilog.

  • Calling a Task in SystemVerilog

As with functions, we must call a task when we want to use it in another part of our SystemVerilog design.

The method we use to do this is similar to the method used to call a function.

However, there is one important difference between calling tasks and functions in SystemVerilog.

When we call a task in SystemVerilog, we can't use it as part of an expression in the same way as we can a function.

We should instead think of task calls as being a short hand way of including a block of code into our design.

As with functions, we can use one of two methods to pass parameters to the task when we call it. The difference between these two methods is the way that we pass data to our task.

The first method which we can use is known as positional association. When we use this approach, we pass parameters to our task in the same order as we declared them.

This is exactly the same as positional association in function calls.

The code snippet below shows how we would use positional association to call the pulse_generate task which we previously considered.

In this case, we map the pulse_length input to the pulse_time variable and the pulse output to the pulse_out variable.

The second method which we can use to call a task in SystemVerilog is known as named association.

When we use this approach, we explicitly declare which input or output we are passing data to. As a result, the order in which we declare the inputs and outputs is not important,

Again, this method is exactly the same as named association in SystemVerilog functions.

The code snippet below shows how we would use named association to call the pulse_generate task which we previously considered.

In this example, we map the pulse_length input to the pulse_time variable and the pulse output to the pulse_out variable.

  • Returning from a Task in SystemVerilog

When we write tasks in SystemVerilog, we may have some instances where we wish to terminate our task before it has fully executed.

For example, we may wish to terminate our task before it has fully executed if an error occurs.

In SystemVerilog, we can use the return keyword to stop execution of a task. When we use the return keyword, our task will exit immediately and our code will start executing from the point where the task was called.

To better demonstrate how this works, let's consider a basic example.

In this example, we write a simple task which displays the simulation time after waiting for a small delay. We will use an input to the task to determine the length of the delay.

However, we also use an if statement which prevents the task from executing when the delay input is 0.

The code snippet below shows how we would implement this example task in SystemVerilog.

We can also simulate this example in EDA playground to show how the task behaves.

To do this, we firstly call the task with an input which is greater than zero. We then call the task again but this time with the delay input set to zero.

The code snippet below shows the code we use to simulate this example task.

The console output below shows the result of running this code in EDA playground.

As we can see from this example, our task displays a message when we call it the first time.

However, our task doesn't display a message when we call the second time. The reason for this is that the return keyword forces the task to stop executing before it reaches the $display macro.

Automatic Tasks in SystemVerilog

We can also use the automatic keyword with SystemVerilog tasks in order to make them reentrant .

As we talked about in the post on SystemVerilog functions , using the automatic keyword means that our simulation tool uses dynamic memory allocation .

As with functions, tasks use static memory allocation by default. This means that our simulator can only run one instance of the task at a time.

In contrast, tasks which use the automatic keyword allocate memory whenever the task is called. The memory is then freed once the task has finished with it.

  • Automatic Task Example

Let's consider a basic example to show how we use automatic tasks and how they differ from normal tasks.

For this example, we will write a simple task which increments the value of a local variable by a specified amount. We use an input to the task to determine how much the local variable is incremented by.

The SystemVerilog code below shows how we would implement this example using a static task.

The code snippet below shows how we implement this task using an automatic task.

As we can see from this, we use practically the same code for both implementations. We have simply included the automatic keyword in the second task to change the way that memory is allocated.

We can then use EDA playground to write a simulation which calls both of these tasks a number of times in order to show the difference between the behavior of automatic and static tasks.

The SystemVerilog code below shows how we implement this simple simulation.

The console output below shows the result of running this simulation.

As we can see from this, the value of the local variable i is stored in a single memory location when we call the static task.

As a result of this, the value of i is persistent and it retains its value between calls to the task.

When we run the task, we increment the value which is already stored in the given memory location.

In contrast, the local variable i is allocated new memory whenever we call the automatic task. After the memory has been allocated, it is then assigned the value of 1.

When the task has finished running, the dynamically allocated memory is freed and the local variable no longer exists.

Automatic Variables in a Task

We can also use the automatic keyword to create variables inside of a SystemVerilog task, as is shown in the code snippet below.

By default, any variables which we declare inside of a task use static memory allocation.

This means that our simulator allocates memory once at the start of our simulation. Our simulator will also never deallocate this memory while a simulation is running.

As a result of this, when we write data to this variable it will either be stored until our simulation finishes executing or until we write new data to it.

In addition to this, any values stored in this memory will maintain their value between calls to the task.

In contrast, our simulator uses dynamic memory allocation when we create automatic variables in our SystemVerilog tasks.

This means that our simulator allocates memory to store the variable whenever we call the task.

Once the task has finished executing, this memory is then deallocated again.

As we can see from this, the main difference between static and automatic variables is their lifetime.

When we declare a static variable, we are telling our tools that we want the variable exist for the entire simulation.

In contrast, when we declare a dynamic variable we are telling our tools that we want to limit the lifetime so that it only exists for as long as our task is executing.

In SystemVerilog, we can declare and use static variables in both static and automatic functions or tasks.

  • Automatic Variable Example

To better demonstrate the difference between static and automatic variables let's consider a basic example.

For this example, we will write a simple task which declares two internal variables that we invert every time we call the task.

In addition to this, we will also include a single input which we use to delay the inversion of these two variables.

One of the variables in this task will be static while the other will be an automatic variable.

The code snippet below shows how we implement this task in SystemVerilog.

We can then simulate this in EDA playground by writing a loop which calls our task three times. The console output below shows the result of this simulation.

We can see from this example that our simulator retains the value of the static variable between calls to the task.

As a result of this, the static_var variable always retains the last value it was assigned to when we call the task.

In contrast, our simulator discards the value of the automatic variable once the task has finished executing.

As a result of this, our simulator sets the value of the automatic variable to 0 every time we call the task.

Passing Parameters by Reference

In the section on calling a task in SystemVerilog, we saw how we pass inputs to a task when we call it.

By default, all of our parameters are  passed by value  when we call a task in SystemVerilog. This means that our task receives it's own individual copy of the data.

As a result, we can modify these values and the changes will not be visible outside of the task.

As we talked about in the post on SystemVerilog functions, we can also pass parameters by reference in SystemVerilog.

Although we are unlikely to use this approach very often, we can also pass parameters to tasks by reference.

When we do this, we no longer create a local copy of the data inside of the task.

Instead, we pass a memory address which tells the task where it can find the data. In effect, we are passing a  pointer   to our data rather than the actual data itself.

As a result of this, any changes which we make to this data inside of our task will also be visible to the rest of our program.

The SystemVerilog code below shows the general syntax we use to declare task which pass data by reference.

As we can see from this, when we want to pass a parameter by reference rather than value then we simply replace the input keyword with the ref keyword.

We use the ref keyword for each argument which we want to pass by reference. This means that we can use a mixture of passing by value and passing by reference in SystemVerilog.

  • Passing by Reference Example

To better demonstrate the difference between passing by value and passing by reference, let's consider a simple example.

In this example, we will write a task which takes two time type inputs and increments their value by 10ns.

We will pass one of the parameters by reference and one by value. After incrementing the values, our task will exit without returning any data.

The code snippet below shows how we would implement this task in SystemVerilog.

We can then use the code below to run a simple simulation which demonstrates how our task affects the two arguments differently.

Running this example on EDA playground results in the console output shown below.

As we can see from this example, our task modifies the value of the parameter when we pass the data by reference.

As we discussed, this is because we are passing a memory location to the task and any changes to the memory are visible to the rest of our program.

In contrast, our task does not affect the value of the parameter when we pass data to the task by value.

Again, we expect this behavior as the data is copied into the task and changes we make to it are not visible to the rest of our program.

There are two main differences between tasks and functions, what are they?

A task can have ore than one output but a function can only have one. A function can not consume time but a task can.

What is the difference between an automatic task and a normal task in SystemVerilog?

Normal SystemVerilog tasks use static memory allocation whereas automatic tasks use dynamic memory allocation

What is the difference between passing a parameter by value and by reference?

When we pass a parameter by value, our task receives it's own copy of the data and any modifications we make are not visible in the rest of our design. When we pass a parameter by reference, our function gets a pointer to the data and changes to the data are visible in the rest of our design.

Write the code for a task which can generate a fixed number of pulses. The task should take three inputs - one which sets the high time of the pulse, one which sets the low time of the pulse and another which determines how many pulses should be generated. (TIP: Use a for loop to generate the pulses).

2 comments on “An Introduction to Tasks in SystemVerilog”

First I'd like to thank you for that really interesting article. I just had a small question about the pulse_generate task. It takes pulse_length in input but uses pulse_time for the waiting statement, is that normal ?

Kind regards,

Hi Camille, I am glad you found the article interesting. That is actually a typo in the pulse_generate task, I have now fixed it.

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

Table of Contents

Don't Miss Out

We are about to launch exclusive video content. Sign up to hear about it first.

  • Using Project Revenue and Billing

How Invoices Are Generated

You can generate invoices by using contracts. Each contract line processes eligible transactions charged to its associated projects and tasks. Invoice amounts are calculated when you either submit the process to generate invoices or manually create an invoice for a contract.

You can generate invoices more quickly by specifying a number of instances of the process that would run in parallel. In the Manage Administrator Profile Values task, use the Number of Parallel Invoice Generation Programs profile option to specify a value between 2 and 5. Each instance processes a subset of the contracts, using a system-generated contract number range.

Settings That Affect Invoice Amounts

Depending on the security settings, the application restricts the business unit and contracts that you can select when you enter the parameters to generate an invoice.

The following table explains several key parameters of the invoice generation process.

How Invoice Lines Are Created

The two major components of invoice generation involve creating the billing transactions and creating the invoice.

The first step of the Generate Invoice process evaluates the eligibility of expenditure items and events for invoicing, maps them to contract lines, and updates the funding amount for the contract line. If an expenditure item or event passes the billing controls, a mapping record is created for a combination of the transaction, contract line, and funded amount. This intermediate mapping record, the billing transaction, is placed on the invoice and is updated each time that you generate an invoice for the contract until the sum of its mappings are 100 percent.

Next, invoice lines and distributions are created from the eligible billing transactions during the Generate Invoice process. Distributions are grouped into invoice lines and the invoice header using the rules defined on the invoice format. Optionally, create distributions manually by attaching the eligible expenditure items and events on the invoice to the invoice lines.

For sponsored projects funded by multiple awards and funding sources, users can invoice sponsors and generate accurate revenue using the costs charged to a specific project and award combination. Cost transactions for sponsored projects store the contract as specific attributes, because there can be multiple awards or contracts for a single sponsored project. This is available only for sponsored project transactions, not for non-sponsored projects or regular, non-award based contracts. When you use this contract on the project cost transaction, the invoice generation and revenue recognition processes now select the project costs specific to the award or contract.

All transactions for an internal funding source are non-billable. Users cannot make any adjustments to an internal funding source cost transaction so as to mark it as a billable transaction.

Related Topics

  • Billing Transactions
  • How Percent Complete Invoice Amounts Are Calculated
  • How Percent Spent Invoice Amounts Are Calculated

IMAGES

  1. Verilog中generate的使用

    verilog task generate

  2. Systemverilog generate : Where to use generate statement in Verilog

    verilog task generate

  3. PPT

    verilog task generate

  4. function and task in verilog with example

    verilog task generate

  5. How to generate a clock in verilog testbench and syntax for timescale

    verilog task generate

  6. Verilog Simulator

    verilog task generate

COMMENTS

  1. hdl

    1 I want to use generate statement inside a task. The following code is giving compile errors (iverilog).

  2. Using Tasks and Functions in Verilog

    November 2, 2020 In this post we look at how we use tasks and functions in verilog. Collectively, these are known as subprograms and they allow us to write verilog code which is reusable. As with most programming languages, we should try to make as much of our verilog code as possible reusable.

  3. Verilog generate block

    A generate block allows to multiply module instances or perform conditional instantiation of any module. It provides the ability for the design to be built based on Verilog parameters.

  4. Writing Reusable Verilog Code using Generate and Parameters

    The verilog code snippet below shows how we would write the interface for the parameterized counter module. module counter # ( parameter BITS = 8; ) ( input wire clock, input wire reset, output reg [BITS-1 : 0] count ); In this example we see how we can use a parameter to adjust the size of a signal in verilog.

  5. Using Generate and Parameters to Write Reusable SystemVerilog Designs

    August 12, 2021 In this blog post we look at the use of SystemVerilog parameters and the generate statement to write code which can be reused across multiple FPGA designs. This includes examples of a parameterized module, a generate for block, generate if block and generate case block.

  6. Verilog Generate: Guide to Generate Code in Verilog

    Verilog Generate is a powerful feature that allows for the creation of multiple instances of a module or conditional instantiation of any module based on Verilog parameters. Understanding Verilog Generate is essential for writing reusable code and increasing design efficiency.

  7. Generate Blocks

    The generate statement in Verilog is a very useful construct that generates synthesizable code during elaboration time dynamically. The simulator provides an elaborated code of the 'generate' block. It provides the below facilities: To generate multiple module instances or code repetition.

  8. SystemVerilog Generate Construct

    Overview The Generate construct is a very useful tool. You'll commonly see it used for these 3 purposes Lazy instantiation of module items using a for-loop Changing the structure or design of a module using SystemVerilog Parameters Using generate with assertions for Functional and Formal Verification Generate Overview

  9. Verilog Task

    Verilog Task A function is meant to do some processing on the input and return a single value, whereas a task is more general and can calculate multiple result values and return them using output and inout type arguments. Tasks can contain simulation time consuming elements such as @, posedge and others. Syntax

  10. Verilog Generate Configurable RTL Designs

    Verilog generate constructs are powerful ways to create configurable RTL that can have different behaviours depending on parameterization. Generate loop allows code to be instantiated multiple times, controlled by an index. Conditional generate, if-generate and case-generate, can conditionally instantiate code.

  11. Task

    Tasks are sections of Verilog code that allow the Digital Designer to write more reusable, easier to read code. Tasks are very handy in testbench simulations because tasks can include timing delays. This is one of the main differences between tasks and functions, functions do not allow time delays.

  12. PDF Tasks, Functions, and Testbench

    2-1-1. Open PlanAhead and create a blank project called lab4_2_1. 2-1-2. Create and add a Verilog module, called add_two_values_function, that defines a function called add_two_values that takes two 4-bit parameters, add them, and return a 5-bit sum. The module will have two 4-bit input ports and one 5-bit output port.

  13. generate loops in Verilog

    Generate Loops in Verilog. Traditional for and while loops are "behavioral" loops. Verilog also supports structural loops that create repeated instances of a submodule, or repeated assignments. This capability uses the generate syntax. As an example, we will implement a classic ripple carry adder using structural syntax.

  14. Writing Reusable Verilog Code using Generate and Parameters

    Writing Reusable Verilog Code using Generate and Parameters In this blog post we look at the use of verilog parameters and the generate statement to write verilog code which is reusable. This includes examples of a parameterized module, a generate for block, generate if block and generate case block.

  15. Tasks and Functions

    Tasks and Functions in Verilog. A function or task is a group of statements that performs some specific action. Both of them can be called at various points to perform a certain operation. They are also used to break large code into smaller pieces to make it easier to read and debug.

  16. PDF Verilog-2001 Quick Reference Guide

    • Identifiers created by an array of instances or a generate block may also contain the characters [ and]. 4.6 Hierarchical Path Names A net, variable, task or function can be referenced anywhere in the design hierarchy using either a full or relative hierarchy path. • A full path consists of the top-level module, followed by any number of

  17. Accessing task of generate block using hierarchy path

    . . . generate genvar i; begin : GEN_MEM_MODEL for (i = 0; i < `WIDTH; i = i+1) begin : MEM_MODEL_INST . . . endmodule Now how can I access method / task of memory model which I have generated using "generate" keyword. While generation it showing name as below : ddr_tb_top.dram_model.GEN_MEM_MODEL.MEM_MODEL_INST [0].i_dram0.

  18. An Introduction to Tasks in SystemVerilog

    The code snippet below shows how we would implement this task in SystemVerilog. task inc_time (ref time x, input time y); x = x + 10ns; y = y + 10ns; endtask : inc_time. We can then use the code below to run a simple simulation which demonstrates how our task affects the two arguments differently.

  19. Variable clock generation in verilog using task

    raghavkumar January 20, 2015, 6:47am 1 I have used following code to generate clock (whichever value i pass through task it will create that frequency), but the code only works if i use CLKSEL_global = clksel_local (line no. 23) (i.e. blocking assignment) but that creates delta delay.

  20. variable clock generation in verilog using task

    I have used following code to generate clock (whichever value I pass through task it will create that frequency), but the code only works if I use CLKSEL_global = clksel_local (i.e. blocking assignment) but that creates delta delay. How do I generate variable clock without introducing delta delay? Is their another way of using a task.

  21. PDF VerilogEval: Evaluating Large Language Models for Verilog Code Generation

    of diverse Verilog coding tasks, ranging from module imple-mentation of simple combinational circuits to complex finite state machines, code debugging, and testbench construction. We focus on generating self-contained3 Verilog modules from natural language text descriptions. We define a Verilog module as self-contained if the module ...

  22. How Invoices Are Generated

    You can generate invoices more quickly by specifying a number of instances of the process that would run in parallel. In the Manage Administrator Profile Values task, use the Number of Parallel Invoice Generation Programs profile option to specify a value between 2 and 5. Each instance processes a subset of the contracts, using a system ...