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Periodic Pulses Pattern

sdb
Beginner
864 Views

Hello,

I'm a new Verilog programmer and still rely on examples to write code.

I didn't find any example of what I need.

I need to generate two pulses periodicaly like this following schema:

PeriodicPulsesPattern.png

clk is the base of the period (pulse every 8 ticks for example).

pulse1: rises 3 ticks after positive edge of clk and falls 2 ticks later.

pulse2: rises 4 ticks after positive edge of clk and falls 3 ticks later.

I'd like also generates the pulses for a limited number (N) of periods, 1 ≤ N < ∞.

I suppose I have to use temporisation conditions (#t) but didn't success to synchronize them to posedge of clk.

Thank for your help.

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7 Replies
Nurina
Employee
839 Views

Hello,


Thank you for using Intel Communities.

Please allow some time while I investigate.


Regards,

Nurina


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Nurina
Employee
837 Views

Hello,


Are you trying to do this for simulation only? Are you trying to have a testbench to show this behaviour?

Can you share what you currently have?


Regards,

Nurina


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sdb
Beginner
812 Views

Thank you to your answer,

Yes it is for a testbench only. I have no result because I didn't find how writing the code to obtain the desired result.

Best regards.

Daniel

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Nurina
Employee
790 Views

Hello,


Can you attach the code you have written so we can work from there?


Thanks,

Nurina


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sdb
Beginner
702 Views
Here are the expected periodicaly outputs of the test bench:
 
pulses.png
 
I tried this code. What is the problem?
 
`timescale 1us/1ns
 
module Pulses(clk, pulse1, pulse2);
 
output clk, pulse1, pulse2;
wire c, p1, p2;
 
initial
begin
  c = 0; 
  p1 = 0;
  p2 = 0;
  repeat(1000)     //1000 cycles repeated
  begin
    #0 c = 1;
    #1 c = 0;
    #2 p1 = 1;
    #1 p2 = 1;
    #1 p1 = 0;
    #2 p2 = 0;
    #1 ;
  end
 
  assign clk = c;
  assign pulse1 = p1;
  assign pulse2 = p2;
 
end
 
endmodule

 

Thank you

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Nurina
Employee
689 Views

Hello,

 

That doesn't look like a testbench. How are you simulating this? Are you using ModelSim/QuestaSim?

I tried using QuestaSim and managed to get the output you want.

First of all, a testbench shouldn't have any ports declaration -> module Pulses(clk, pulse1, pulse2);

It should be empty like so -> module Pulses ();

And I don't think you can use assign in testbench.

 

Please refer to the verilog files I'm attaching. periodic_pulses.v is the top verilog file in your Quartus project and periodic_pulses_tb.v is the testbench.

Follow the steps here to compile and run simulation, it should be the same for Quartus Lite:

QuestaSim: https://www.intel.com/content/www/us/en/docs/programmable/703090/21-1/simulation-quick-start.html

ModelSim: https://www.intel.com/content/www/us/en/docs/programmable/683248/18-0/simulation-quick-start.html

 

Regards,

Nurina

 

p/s: If any answer from the Intel Support is helpful, please feel free to provide rating with 4/5 survey on the support provided.

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FvM
Valued Contributor III
636 Views

Hello,

apart from the point that outputs have no purpose in a testbench, the problem in your original code are of different kind.

Assignment must take place outside the initial statement.

 

`timescale 1us/1ns

module Pulses(clk, pulse1, pulse2);

output reg clk, pulse1, pulse2;
reg c, p1, p2;

initial
begin
c = 0;
p1 = 0;
p2 = 0;
repeat(1000) //1000 cycles repeated
begin
#0 c = 1;
#1 c = 0;
#2 p1 = 1;
#1 p2 = 1;
#1 p1 = 0;
#2 p2 = 0;
#1 ;
end
end

assign clk = c;
assign pulse1 = p1;
assign pulse2 = p2;

endmodule

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