Transact-SQL
Reinforcement Learning
R Programming
React Native
Python Design Patterns
Python Pillow
Python Turtle
Verbal Ability
Interview Questions
Company Questions
Artificial Intelligence
Cloud Computing
Data Science
Machine Learning
Data Structures
Operating System
Computer Network
Compiler Design
Computer Organization
Discrete Mathematics
Ethical Hacking
Computer Graphics
Software Engineering
Web Technology
Cyber Security
C Programming
Control System
Data Mining
Data Warehouse
Find centralized, trusted content and collaborate around the technologies you use most.
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
Get early access and see previews of new features.
now I know in Verilog, to make a sequential logic you would almost always have use the non-blocking assignment (<=) in an always block. But does this rule also apply to internal variables? If blocking assignments were to be used for internal variables in an always block would it make it comb or seq logic?
So, for example, I'm trying to code a sequential prescaler module. It's output will only be a positive pulse of one clk period duration. It'll have a parameter value that will be the prescaler (how many clock cycles to divide the clk) and a counter variable to keep track of it.
I have count's assignments to be blocking assignments but the output, q to be non-blocking. For simulation purposes, the code works; the output of q is just the way I want it to be. If I change the assignments to be non-blocking, the output of q only works correctly for the 1st cycle of the parameter length, and then stays 0 forever for some reason (this might be because of the way its coded but, I can't seem to think of another way to code it). So is the way the code is right now behaving as a combinational or sequential logic? And, is this an acceptable thing to do in the industry? And is this synthesizable?
You should follow the industry practice which tells you to use non-blocking assignments for all outputs of the sequential logic. The only exclusion are temporary vars which are used to help in evaluation of complex expressions in sequential logic, provided that they are used only in a single block.
In you case using 'blocking' for the 'counter' will cause mismatch in synthesis behavior. Synthesis will create flops for both q and count . However, in your case with blocking assignment the count will be decremented immediately after it is being assigned the prescaled value, whether after synthesis, it will happen next cycle only.
So, you need a non-blocking. BTW initializing 'count' within declaration might work in fpga synthesis, but does not work in schematic synthesis, so it is better to initialize it differently. Unless I misinterpreted your intent, it should look like the following.
You do not need temp vars there, but you for the illustration it can be done as the following:
Reminder: Answers generated by artificial intelligence tools are not allowed on Stack Overflow. Learn more
Post as a guest.
Required, but never shown
By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .
COMMENTS
The RHS of every non-blocking statement of a particular time-step is captured, and moves onto the next statement. The captured RHS value is assigned to the LHS variable only at the end of the time-step. Simulation Log. ncsim> run. [0] a= 0xx b= 0xx c= 0xx. [0] a= 0xx b= 0xx c= 0xx. [0] a= 0xx b= 0xx c= 0xx.
The Blocking assignment immediately takes the value in the right-hand-side and assigns it to the left hand side. Here's a good rule of thumb for Verilog: In Verilog, if you want to create sequential logic use a clocked always block with Nonblocking assignments. If you want to create combinational logic use an always block with Blocking ...
Evaluate b&(~c) but defer assignment of z 1. Evaluate a | b, assign result tox x 2. Evaluate a^b^c, assign result to y 3. Evaluate b&(~c), assign result to zz I. Blocking vs. Nonblocking Assignments • Verilog supports two types of assignments within always blocks, with subtly different behaviors. • Blocking assignment: evaluation and ...
The conventional Verilog wisdom has it all wrong. There is no problem with using blocking assignments for a local variable. However, you should never use blocking assignments for synchronous communication, as this is nondeterministic. A non-blocking assignment within a clocked always block will always infer a flip-flop, as dictated by the ...
The blocking assignment statements are executed sequentially by evaluating the RHS operand and finishes the assignment to LHS operand without any interruption from another Verilog statement. Hence, it blocks other assignments until the current assignment completes and is named as "blocking assignment".
Blocking And Nonblocking In Verilog. Blocking Statements: A blocking statement must be executed before the execution of the statements that follow it in a sequential block. In the example below the first time statement to get executed is a = b followed by. Nonblocking Statements: Nonblocking statements allow you to schedule assignments without ...
Non-Blocking assignments. Nonblocking assignments (<=), which follow each other in the code, are started in parallel. The right hand side of nonblocking assignments is evaluated starting from the completion of the last blocking assignment or if none, the start of the procedure. The transfer to the left hand side is made according to the delays.
Blocking and Non-blocking Assignment in Verilog. When working with behavioural modeling in Verilog, there are two types of assigment which is known as blocking and non blocking assigment and both of them there is a operator, '=' operator for blocking assignment and '=' operator for non blocking assigment.At short, blocking assignment executes one by one sequentially and non-blocking assignemnt ...
In this Verilog tutorial, we demonstrate the usage of Verilog blocking and nonblocking assignments inside sequential blocks.Complete example from the Verilog...
Blocking vs Non-Blocking Assignments • Blocking (=) and non-blocking (<=) assignments are provided to control the execution order within an always block. • Blocking assignments literally block the execution of the next statement until the current statement is executed. - Consequently, blocking assignments result in ordered statement ...
The significance of blocking and non-blocking assignments in Verilog coding cannot be overstated. These elements serve as the foundation for precise and effective digital circuit design, offering ...
was fairly sure that nonblocking assignments were sequential while blocking assignments were parallel. Blocking assignment executes "in series" because a blocking assignment blocks execution of the next statement until it completes. Therefore the results of the next statement may depend on the first one being completed. Non-blocking assignment ...
Blocking assignments in Verilog follow a sequential execution model, where each assignment is executed one after the other. This means that a blocked assignment must complete before the next assignment in the same procedural block can begin. Consequently, changes made to variables within a blocking assignment immediately affect subsequent ...
An edge-sensitive intra-assignment timing control permits a special use of the repeat loop. The edge sensitive time control may be repeated several times before the delay is completed. Either the blocking or the non-blocking assignment may be used. always always @(IN) @(IN) OUT OUT <= <= repeat.
20 October 2020. Blocking / Non-Blocking assignment rules. The main reason to use either Blocking or Non-Blocking assignments is to generate either combinational or sequential logic. In non-blocking assignments (<=), all registers inside the always block are updated at the end. In blocking assignments (=), the registers are updated immediately.
There are synthesis differences between a blocking statement and a non-blocking statement. Blocking Assignment. The syntax for a blocking assignment is: always @ (pos edge clk) begin. x=y; y=z; end. In this blocking assignment immediately after rising transition of the clk signal, x=y=z.
Verilog supports blocking and non-blocking assignments statements within the always block with their different behaviors. The blocking assignment is similar to software assignment statements found in most popular programming languages. The non-blocking assignment is the more natural assignment statement to describe many hardware systems ...
In Verilog, blocking and non-blocking assignments are two different ways to assign values to variables.A blocking assignment, represented by the "=" sign, as...
When using the blocking (=) assignment the value is available to use in the next line of code.This implies it is combinatorial and not driven from a flip-flop. In simulation it looks like it is driven from a flip-flop because the block is only evaluated on positive clock edge, in reality it is not which might break the interface.
1. You should follow the industry practice which tells you to use non-blocking assignments for all outputs of the sequential logic. The only exclusion are temporary vars which are used to help in evaluation of complex expressions in sequential logic, provided that they are used only in a single block. In you case using 'blocking' for the ...