for loops in Verilog

For loops in verilog.

A for loop in Verilog is similar to the for loop in C. Most often a Verilog loop is used for combinational logic , comprised of blocking assignments ( = as opposed to <= ). A simple example is given in src/add_bits.v , which computes the sum over all bits in a vector:

The lines in this block are evaluated sequentially, one after the other. Imagine the successive evaluations laid out like dominos. Although they are evaluated in sequence, the whole sequence must complete – every domino must fall – before the next clock cycle arrives. After synthesis, the circuit looks like a lineup of combinational adders:

Assigned Tasks

Create a top module to contain add_bits as a submodule instance. In the top module, do the following:

  • Declare top level inputs clk , load , (1 bit), and a (8-bits)
  • Declare top level output q (4 bits)
  • Declare an internal 8-bit reg named _a (the underscore ( _ ) distinguishes it as a separate wire from the port a )
  • Declare an internal 4-bit wire named _q
  • Instantate the add_bits module, and name the instance add_bits_instance
  • _a to add_bits_instance.a
  • _q to add_bits_instance.q
  • Always assign q <= _q
  • if load is 1, then assign _a <= a

A testbench template is provided in src/testbench.v . Modify the testbench to test your top module. Specifically, you need to declare a wire for q , instantiate top , connect its ports, and make additional $write and $fwrite statements to report q in the log text. Simulate your design to verify that q is correct for several random values of a .

When verified, create an XDC file (use Basys3_Master.xdc as a template) and map a to the lower (right-most) switches, load to btnU , and q to the lower 4 led signals. Edit build.tcl as needed, then implement the design .

Open the timing report and note the WNS.

Program your design onto the Basys3 board and test the following cases:

  • a = 8'b0000_0001
  • a = 8'b0101_0101
  • a = 8'b1111_1111

Save a photo of your board for each test case, with filenames case1 , case2 , and case3 . Save the photo files with the appropriate graphics file suffix ( .png , .jpg , etc).

Turn in your work using git :

Indicate on Canvas that your assignment is done.

  • The Verilog-AMS Language
  • Continuous Assigns

Continuous Assigns 

A module may have any number of continuous assign statements. Continuous assign statements are used to drive values on to wires. For example:

This is referred to as a continuous assign because the wire on the left-hand side of the assignment operator is continuously driven with the value of the expression on the right hand side. The target of the assign statement must be a wire. The continuous assign statement is not a procedural statement and so must be used at the module level; it cannot be placed in an initial or always process.

You can add delay to a continuous assign statement as follows:

In this case, the value of a changes 10 units of time after the expression b & c changes. Continuous assign statement implement inertial delay, meaning that continuous assign statements swallow glitches. This is illustrated below with the assumption that the unit of time is 1ns.

../../_images/inertial-delay.png

It is possible to specify up to three delay values on a continuous assignment:

When you specify more than one:

The first delay refers to the transition to the 1 value (rise delay).

The second delay refers to the transition to the 0 value (fall delay).

The third delay refers to the transition to the high-impedance value.

When a value changes to the unknown (x) value, the delay is the smallest of the delays specified.

If only two delays are specified, then the delay to high-impedance is the smallest of the two values specified.

Verilog Continuous Assignment Statements Tutorial

Continuous assignment statements are an essential aspect of Verilog that allows you to assign values to signals without using procedural blocks. Unlike procedural assignments found in always blocks, continuous assignments are used for modeling combinational logic. In this tutorial, we will explore continuous assignment statements in Verilog and learn how to use them to describe the behavior of combinational circuits efficiently.

Introduction to Continuous Assignment Statements

Continuous assignment statements in Verilog are used to specify the relationship between input and output signals in a combinational circuit. They allow you to assign a value to a signal continuously, meaning the assignment is continuously evaluated as the inputs change. Continuous assignments are used outside procedural blocks and are ideal for describing combinational logic or interconnections between signals.

Example of Continuous Assignment Statements:

Another example:, steps to use continuous assignment statements.

To use continuous assignment statements in Verilog, follow these steps:

  • Identify the combinational logic relationship between input and output signals.
  • Use the 'assign' keyword to create a continuous assignment statement.
  • Specify the output signal on the left-hand side and the combinational logic expression on the right-hand side of the assignment.
  • Ensure that the right-hand side expression does not contain any procedural constructs, as continuous assignments are not allowed to contain procedural statements.
  • Continuous assignments are evaluated in parallel with no explicit sequencing, making them suitable for combinational logic modeling.

Common Mistakes with Continuous Assignment Statements

  • Using procedural statements such as if-else or case statements within continuous assignments.
  • Missing the 'assign' keyword before the continuous assignment statement, leading to syntax errors.
  • Attempting to use continuous assignments for modeling sequential logic, which is not their intended use.
  • Using continuous assignments for outputs in modules with procedural assignments, leading to unexpected behavior.
  • Not considering the propagation delays of combinational logic when using continuous assignments, which may affect simulation results.

Frequently Asked Questions (FAQs)

  • Q: Can I use continuous assignments inside an always block? A: No, continuous assignments are not allowed inside always blocks. They are used outside procedural blocks to model combinational logic.
  • Q: What is the difference between continuous assignments and procedural assignments? A: Continuous assignments are evaluated continuously for combinational logic, while procedural assignments in always blocks are used for modeling sequential logic that executes based on clock edges or event triggers.
  • Q: Can I use continuous assignments for bidirectional signals? A: No, continuous assignments can only be used for assigning values to output or wire signals, not bidirectional signals or registers.
  • Q: How do continuous assignments affect the simulation time of a Verilog design? A: Continuous assignments add negligible overhead to the simulation time as they represent combinational logic and are evaluated in parallel with no explicit sequencing.
  • Q: Can I use continuous assignments for modeling arithmetic operations? A: Yes, continuous assignments can be used to model arithmetic operations in combinational logic. For example, you can use continuous assignments to describe the addition or subtraction of signals.
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An Introduction to Verilog Data Types and Arrays

In this post, we talk about the most commonly used data types in Verilog. This includes a discussion of data respresentation , net types , variables types , vectors types and arrays .

Although verilog is considered to be a loosely typed language, we must still declare a data type for every port or signal in our verilog design.

The type which we specify is used to define the characteristics of our data.

We can use types which interpret data purely as logical values, for example. We can also use types which interpret our data as if it were a numeric value.

When we assign data to a signal in verilog, the data is implicitly converted to the correct type in most cases. As a result, there is often no need necessary to explicitly perform type conversions in verilog.

  • Respresenting Data in Verilog

When we write verilog, we often need to represent digital data values in our code. We can express this data as either a binary , hexadecimal or octal value.

Unlike in other programming languages, we also need to define the number of bits we have in our data representation.

This is because we are fundamentally describing hardware circuits when we use verilog. Therefore, we can create data busses which contain as many bits as we choose.

The code snippet below shows the general syntax for representing digital data in verilog.

We use the <bits> field to indicate the number of bits in the data that we are representing.

We use the <representation> field to indicate how our data is represented. This field can be set to b (for binary), h (for hex), o (for octal) or d (for decimal).

Finally, we use the <value> field to set the actual value of the data.

The code snippet below shows how we represent the decimal value of 8 using each of the different valid reprentations.

Basic Data Types in Verilog

Broadly speaking, the basic data types in verilog can be split into two main groups - net types and variable types .

We use these two different groups to model different elements of our digital circuits.

We use the net types to model connections in our digital circuits. They are unable to store values on their own and must be driven with data.

We primarily use the variable types to model registers or flip flops in our design. These types can store data, meaning that their behaviour is similar to variables in other programming languages such as C.

Regardless of the exact type we are using, there are four valid values we can assign to individual bits in our data. These four different values are shown in the table below.

We use the same syntax to declare a variable in verilog, regardless of the exact type. The code snippet below shows this general syntax.

We use the <type_name> field in the above example to declare the type of variable we have. We simply replace this field with the name of the type.

As an example, the verilog code below declares an integer type variable and assigns it a value of 100.

Net Types in Verilog

We use the net data types in verilog to describe the physical connections between different components in our design. As a result of this, net types on their own can not be used to store data values or drive data.

To better demonstrate when we would use a net type, consider the circuit diagram shown below.

In this circuit, we would use a net type to connect the output of the multiplexor to the input of the flip flop.

We normally use continuous assignment to drive data onto a wire type. To do this we must use the assign keyword, as shown in the code snippet below. We talk about continuous assignment in more detail in a later post.

We can not use net types in procedural code such as always blocks . The always block is discussed in more detail in a later blog post.

  • Wire Type in Verilog

The most commonly used net type in verilog is the wire type which we discussed in the previous post.

We use the wire type in verilog to declare signals which are very basic point to point connections in our design. As the name suggests, they are roughly equivalent to an electrical wire in a traditional circuit.

The verilog code below shows how we use the wire type together with the assign keyword.

  • wand & wor Types

Although the wire type is the most commonly used of the net data types, there are several other types of net which we can use in our verilog designs.

The wand and the wor net types are used to insert basic logic gates into our circuit. We use the wand to insert an and gate and the wor type to create an or gate.

When we use the wand and wor types, we must assign the signal more than once. We do this as each of the assignments represents one input to the underlying logic gate.

The verilog code below shows how we use the wand and wor types together with the assign keyword.

As we will see in a later post, we can easily use the wire type to model combinational logic in verilog . As a result of this, the use of the wor and wand types is not recommended.

  • tri, triand & trior Types

In addition to the wire, wand and wor state, we can also use an equivalent tri, triand or trior type.

We use these types in the exact same way as the wire, wand and wor types. In fact, the functionality of these types is exactly the same. However, we can use them to more clearly show the intent of our design.

The code snippet below shows a basic example where the tri type is driven to high impedance .

However, as the wire type can also can take tristate values, we rarely use the tri type in practise. The same is also true with the trior and triand types, which can also easily be replicated using the wire type in our verilog designs.

  • supply0 & supply1 Types

The final net types which we can use in our verilog designs are the supply0 and supply1 types.

We can use these types to tie our signal to a constant value of either binary 1 or 0. As this has the effect of creating a net which is tied to either ground or Vcc , we don't need to assign any data to this type.

The code snippet below shows how we use these types to create a signal which is tied either high or low.

However, we rarely need to tie a signal high or low in our design and when we do, it is simple to accomplish using a wire type. Therefore, the supply0 and supply1 types are rarely used in practise.

Variable Types in Verilog

Unlike net types, we use variable data types in verilog to store values. When we assign a value to a variable type it maintains this value until it is assigned again.

The variable types are generally more intuitive to understand than net types as they behave in a similar manner to variables in languages such as C .

To better demonstrate when we would use a variable type, consider the circuit diagram shown below.

In this circuit, we would use a variable type to model the flip flop output as it effectively stores a single bit of data.

We must use variable types within blocks of procedural code such as an always block , as shown in the code snippet below which models a D type flip flop .

  • Reg Type in Verilog

The most commonly used variable type in verilog is the reg type. We can use this type whenever we need to store a value in our design.

We most commonly use the reg type to model the behaviour of flip flops.

However, the reg type can also be used to model combinational logic in verilog in some circumstances.

We discuss the use of the reg type for modelling both types of logic in more detail in the post on the verilog always block .

The verilog code snippet below shows how we use the reg type to model a basic flip flop.

Numeric Variable Types

The types which we have looked at so far are all used with single bits of data. However, we can also represent data numerically in our verilog designs.

In verilog, there are two commonly used numeric types - the integer type and the real type . Let's take a closer a look at both of these types.

  • Verilog Integer Type

The most commonly used type for numerical data in verilog is the integer type. However, we normally use this for internal signals in a module rather than for ports. 

By default, the integer is a 32 bit 2s complement number which we can use to represent any whole number in our verilog design.

When we use an integer type, we assign numerical rather than binary values to the variable.

As we can also assign numeric values to the reg type, we typically use integers for constants or loop variables in verilog.

Our synthesis tools will automatically trim any unused bits in our integer type. For example, if we declare an integer constant with a value of 255 then our synthesis tool will trim this down to 8 bits.

The code snippet below shows how we declare and assign an integer type in verilog.

  • Verilog Real Type

In addition to the integer type, we can also use the real type in verilog. We use this type to store non-integer numbers, i.e. numbers which also have a decimal part.

The real type is typically implemented as a 64 bit floating point number in verilog. As a result of this, it can't be directly synthesized and we typically only use the real type in our verilog testbenches .

We can use either decimal or scientific notation to assign values to the real type.

The code snippet below shows how we declare a real type and assign data to it.

  • Vector Types in Verilog

With the exception of the numerical types, all of the types which we have looked at so far consist of a single bit.

However, we often use data busses to transfer data within a digital circuit.

In verilog, we can use vector types to create data buses. This allows us to declare a signal which has more than one bit.

The code snippet below shows the general syntax which we use to declare a vector type in verilog.

When we define the size of the vector we must specify the most significant and least significant bits (MSB and LSB). Therefore, the <size> field takes the form [MSB:LSB].

For example, to declare a 4 bit little endian type vector we would use the construct [3:0].

As we talked about earlier in this post, we can represent data using binary, hex, octal or decimal formats. When we assign data to a vector we can use any of these representations.

The verilog code below shows how we would declare a 4 bit wide reg type. We also see how we can use the different data representations to assign the value of 1010b to the variable.

  • Signed and Unsigned Data in Verilog

Prior to the release of the verilog 2001 standard all variable and net types could only be used to store unsigned data types.

Similarly, the integer type was always interpreted as a signed value.

However, the signed and unsigned keywords were introduced as a part of the verilog 2001 standard. This allows us to change the way our variable interprets data.

When we declare a type as signed in verilog, it is interpreted as a 2's complement number. This means that we can assign negative numbers to these signals.

By default, the integer type is signed whilst both the reg and wire types are unsigned. We only need to use these keywords if we wish to modify this default behaviour.

The verilog code below shows how we can declare signed and unsigned data using the reg, wire and integer types. In this case, all of the variables which we declare are 32-bits wide.

Arrays in Verilog

We can also create and use array types in verilog. These are particularly useful in the modelling of memories.

In order to declare an array in verilog, we simply add an extra field after the variable name which declares how many elements there are in our array.

This declaration takes the same format as the vector size field which we talked about previously.

The code snippet below shows the general syntax which we use to declare an array type in verilog. We use the <elements> field to declare the size of our array.

As an example, let's say we want to create an array of 3 bit reg types. We want to have a total of 8 elements in the array. The verilog code below shows how we would create this array.

We can access individual elements in the array type using square brackets. For example, the verilog code below shows how we would assign the value of 5h to the final element in our example array.

We can also simulate this example on EDA playground .

  • Multi Dimensional Arrays

In the verilog 1995 standard , it is only possible for us to create one dimensional arrays such as those we used in the previous section.

However, we can also create arrays which have more than one dimension when we use the verilog 2001 standard.

To do this, we simply add another field which defines the number of elements we need.

The code snippet below shows the general syntax we would use to create a 2D array in verilog.

As an example, let's consider the case where we want to modify the size of the array from our previous example.

We now want to create a variable which can store 2 elements both of which have 8 4 bit reg type elements.

To do this, we simply add an extra field to the end of our declaration. The code snippet below shows how we would do this.

We also use the same method to assign a multidimensional array as we would for a 1D array. However, we now use a pair of square brackets to define the element in both dimensions of the array.

As an example, suppose we want to assign the value of 0xa to the the last element in both dimensions. The verilog code below shows how we would assign data to this element in our array.

Which types of data can we represent in our verilog design?

Binary, hexidecimal, octal and decimal. We can also represent decimal numbers but this is not synthesizable.

What are the two main data types in verilog? What is the difference between them?

Net types are used to model connections in our design and can’t store values. Variable types can store data values and behave like variables in other programming languages.

Which type do we most commonly use to model point to point connections in verilog?

The wire type

Which type do we most commonly use to model the behaviour of storage elements like flip flops?

The reg type.

Name the two different types of numeric types. What are the differences between them?

The integer type represents whole numerical values. The real type can be used to represent decimal values as well.

Write the code to declare an 8 bit wire type and assign it the value of AAh.

Declare an array of 16 bit reg types. The array should have a total of 4 elements. Assign the value of FFFFh to the first element in the array and AAAAh to the fourth element in the array.

2 comments on “An Introduction to Verilog Data Types and Arrays”

reg[16:0] example [3:0]; Should be reg [15:0] Not a serious one but it's worth correcting for the sake of neatness..:)

Thanks for pointing out the mistake, it has been corrected now.

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Verilog Tutorial

Verilog code example, what is verilog .

Verilog is a hardware description language (HDL) that is used to describe digital systems and circuits in the form of code. It was developed by Gateway Design Automation in the mid-1980s and later acquired by Cadence Design Systems.

Verilog is widely used for design and verification of digital and mixed-signal systems, including both application-specific integrated circuits (ASICs) and field-programmable gate arrays (FPGAs). It supports a range of levels of abstraction, from structural to behavioral, and is used for both simulation-based design and synthesis-based design.

The language is used to describe digital circuits hierarchically, starting with the most basic elements such as logic gates and flip-flops and building up to more complex functional blocks and systems. It also supports a range of modeling techniques, including gate-level, RTL-level, and behavioral-level modeling.

What was used before Verilog ?

Before the development of Verilog, the primary hardware description language (HDL) used for digital circuit design and verification was VHDL (VHSIC Hardware Description Language). VHDL was developed in the 1980s by the U.S. Department of Defense as part of the Very High-Speed Integrated Circuit (VHSIC) program to design and test high-speed digital circuits.

VHDL is a complex language that enables designers to describe digital systems using a range of abstraction levels, from the low-level transistor and gate levels up to complex hierarchical systems. It was designed to be more descriptive and flexible than earlier HDLs, such as ABEL (Advanced Boolean Expression Language), ISP (Integrated System Synthesis Procedure), and CUPL (Compiler for Universal Programmable Logic).

Despite the development of Verilog and its increasing popularity since the 1980s, VHDL remains a widely used HDL, particularly in Europe and in the military and aerospace industries. Today, both Verilog and VHDL are widely used in digital circuit design and verification, with many companies and organizations using a combination of the two languages.

Why is Verilog better than its predecessor languages ?

Verilog introduced several important improvements over its predecessor languages, which helped make it a more popular and effective HDL for digital circuit design and verification. Here are a few reasons why Verilog is considered better than its predecessor HDLs:

How is Verilog useful ?

Verilog creates a level of abstraction that helps hide away the details of its implementation and technology.

For example, the design of a D flip-flop would require the knowledge of how the transistors need to be arranged to achieve a positive-edge triggered FF and what the rise, fall and clk-Q times required to latch the value onto a flop among many other technology oriented details. Power dissipation, timing and the ability to drive nets and other flops would also require a more thorough understanding of the physical characteristics of a transistor.

Verilog helps us to focus on the behavior and leave the rest to be sorted out later.

The following Verilog code describes the behavior of a counter. The counter counts up if the up_down signal is 1, and down if its value is 0. It also resets the counter if the signal rstn becomes 0, making it an active-low reset.

The simple example shown above illustrates how all the physical implementation details (interconnection of underlying logic gates like NAND and NOR) have been hidden while still providing a clear idea of how the counter functions.

ctr is a module that represents an up/down counter, and it is possible to choose the actual physical implementation of the design from a wide variety of different styles of flops optimized for area, power and performance. They are usually compiled into libraries and will be available for us to select within EDA tools at a later stage in the design process.

How is Verilog different from software languages like C and Java ?

Verilog is a hardware description language (HDL) used to describe digital circuits and systems, while C and Java are software programming languages used to write code that runs on general-purpose computers. Here are some of the main differences between Verilog and programming languages like C and Java:

Overall, Verilog is a specialized language designed specifically for digital circuit design and isn't used for general-purpose programming like C and Java. While there are some similarities in syntax and programming concepts between these languages, the primary focus and application of Verilog is on the design, simulation, and implementation of digital circuits and systems.

What may replace Verilog in the future ?

It's difficult to predict exactly what may replace Verilog in the future, but there are several emerging technologies and languages that may have an impact on the future of digital system design and verification.

One technology that may affect the future of digital system design is High-Level Synthesis (HLS), which is a technique for automatically generating hardware designs from high-level descriptions in languages like C, C++, and SystemC. HLS allows designers to express their design intents and functionality at a higher level of abstraction, rather than specifying the details of logic gates and register transfers in Verilog or VHDL. This could enable more efficient and rapid design of digital systems, and allow designers to explore more design space in a shorter period of time.

Another technology that may impact the future of digital system design is machine learning and artificial intelligence (AI), which have the potential to significantly streamline the design and verification process of digital systems. For example, machine learning algorithms can be used to automatically optimize and generate hardware designs, reducing the need for manual design efforts.

There are also emerging HDLs that are trying to address some of the limitations of Verilog and VHDL, such as Chisel and MyHDL, which are based on more modern programming concepts and provide higher-level abstractions.

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  1. Verilog assign statement

    In Verilog, this concept is realized by the assign statement where any wire or other similar wire like data-types can be driven continuously with a value. The value can either be a constant or an expression comprising of a group of signals. Assign Syntax

  2. verilog

    -1 I'm trying to assign I/O vectors inside a for loop in order to save space. I am unsure if this is not possible or I am running into a syntax issue. I have tried using generate and am still running into issues My current code is as follows:

  3. Verilog Assignments

    force release Placing values onto nets and variables are called assignments. There are three basic forms: Procedural Continuous Procedural continuous Legal LHS values An assignment has two parts - right-hand side (RHS) and left-hand side (LHS) with an equal symbol (=) or a less than-equal symbol (<=) in between.

  4. PDF Intro to Verilog

    Microsoft PowerPoint - L03_Verilog v2.pptx. Intro to Verilog. • Wires - theory vs reality (Lab1) • Hardware Description Languages. • Verilog -- structural: modules, instances -- dataflow: continuous assignment -- sequential behavior: always blocks -- pitfalls -- other useful features. Reminder: Lab #1 due by 9pm tonight.

  5. for loops in Verilog

    For Loops in Verilog. A for loop in Verilog is similar to the for loop in C. Most often a Verilog loop is used for combinational logic, comprised of blocking assignments ( = as opposed to <= ). A simple example is given in src/add_bits.v, which computes the sum over all bits in a vector: The lines in this block are evaluated sequentially, one ...

  6. verilog

    1 Answer Sorted by: 4 Sure you can, just use the always @ (*) construct (you need to make it a reg ). You can handle inout ports easily too. reg res; assign inout_port = dir_out? res: 1'bz; always @ (*) begin if (x == 42 && y != z) res = 10; else res = y * 12; end Share Cite Follow answered Apr 10, 2012 at 12:19 avakar 3,044 2 18 18

  7. Using Continuous Assignment to Model Combinational Logic in Verilog

    We normally use the assign keyword when we want to use continuous assignment in verilog. This approach is known as explicit continuous assignment. The verilog code below shows the general syntax for continuous assignment using the assign keyword. assign <variable> = <value>;

  8. Assignment Statements

    Blocking Assignment. A blocking assignment evaluates the expression on its right hand side and then immediately assigns the value to the variable on its left hand side: a = b + c; It is also possible to add delay to a blocking assignment. For example: a = #10 b + c; In this case, the expression on the right hand side is evaluated and the value ...

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  10. An Introduction to Loops in Verilog

    Loops in Verilog. We use loops in verilog to execute the same code a number of times. The most commonly used loop in verilog is the for loop. We use this loop to execute a block of code a fixed number of times. We can also use the repeat keyword in verilog which performs a similar function to the for loop.

  11. Assignment Statements

    Assignment. A assignment evaluates the expression on its right hand side and then immediately assigns the value to the variable on its left hand side: a = b + c; The target (left side) of an analog assignment statement may only be a integer or real variable. It may not be signal or a wire.

  12. PDF Basic Verilog

    ECE 232 Verilog tutorial 9 Verilog Statements Verilog has two basic types of statements 1. Concurrent statements (combinational) (things are happening concurrently, ordering does not matter) Gate instantiations and (z, x, y), or (c, a, b), xor (S, x, y), etc. Continuous assignments assign Z = x & y; c = a | b; S = x ^ y 2. Procedural statements ...

  13. Continuous Assigns

    Continuous assign statements are used to drive values on to wires. For example: assign a = b & c; This is referred to as a continuous assign because the wire on the left-hand side of the assignment operator is continuously driven with the value of the expression on the right hand side. The target of the assign statement must be a wire.

  14. Verilog Continuous Assignment Statements Tutorial

    To use continuous assignment statements in Verilog, follow these steps: Identify the combinational logic relationship between input and output signals. Use the 'assign' keyword to create a continuous assignment statement.

  15. If statement and assigning wires in Verilog

    3 Answers Sorted by: 11 wire s can only be assigned by assign statements, which can not be used with if statements. If you change x to reg type, then you will be able to assign it in an always block.

  16. An Introduction to Verilog Data Types and Arrays

    July 7, 2020 In this post, we talk about the most commonly used data types in Verilog. This includes a discussion of data respresentation, net types, variables types, vectors types and arrays. Although verilog is considered to be a loosely typed language, we must still declare a data type for every port or signal in our verilog design.

  17. Verilog Tutorial

    Verilog is a hardware description language (HDL) that is used to describe digital systems and circuits in the form of code. It was developed by Gateway Design Automation in the mid-1980s and later acquired by Cadence Design Systems. Verilog is widely used for design and verification of digital and mixed-signal systems, including both ...

  18. Verilog reg assignment?

    2 Answers Sorted by: 10 Are reg types only assigned in always@ block? No, reg types can be assigned in always blocks and initial blocks (plus task and function but I'll skip them in the scope of this question)