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Altera_Forum's avatar
Altera_Forum
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7 years ago

modelsim does not generate clock signal

Hello,

I am trying to use testbenches in a big project. Quartus created tb itself and I just added a few lines within this testmodule:

initial begin

clk_clk = 0;

end

always# 10 clk_clk = ~clk_clk

Then by using RTL simulation I opened modelsim which added all wires of the project correctly but it is not simple generate clock

pic related

1) I did not find any explanation about grey lines. Why it even Pu0 (pull down?)

2) What did i wrong? I tried to follow altera RTL simulation guide

Looking forward any help :c i am very new to Quartus

11 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    7 years ago

    It seems like Modelsim dont see my "always" blocks in testbench at all. Anything i write is not show up during RTL simulation

  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    Hi,

    --- Quote Start ---

    initial begin

    clk_clk = 0;

    end

    always# 10 clk_clk = ~clk_clk

    --- Quote End ---

    Let me know,

    1. Are you able to compile Design & Testbench successfully?

    2. All Inputs/Outputs are declared & initialized properly or not(declaration of clk_clk should be reg)?

    3. can you provide code?

    Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

    Best Regards

    Vikas Jathar

    (This message was posted on behalf of Intel Corporation)
  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    Meaning did you instantiate your design under test in this testbench?

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    7 years ago

    Thank you for all replies!

    Well. Firtsly I created Testbench skeleton by Processing -> Start -> Test bench Writer

    Then i added its link in Assingments -> Settings -> Simulation -> Native link settings

    I modified TB with a few lines for modelsim to generate clock signal (just to try how it works)

    But it is not work, even if i try to assing anything to 1'b1 or whatever.

    Please guide how it supposed to work :c

    clk_clk generated as reg
  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    Hi,

    Replace sysclk by sysclk_period

    It`s simple just provide input stimulus for example as follows & simulate, 

    always @(posedge SYSCLK_PERIOD) begin
# 5 reset_reset_n = 1;
# 50 reset_reset_n = 0;
# 100 reset_reset_n = 1;
# 25 reset_reset_n = 0;
# 55 reset_reset_n = 1;
end

    find the attachment for screenshot.

    Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

    Best Regards

    Vikas Jathar

    (This message was posted on behalf of Intel Corporation)
  • Altera_Forum's avatar
    Altera_Forum
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    7 years ago

    I replaced but still getting those strange pictures. I am sorry, but clock_period is a parameter (constant) how you made it posedge? Could you please provide me with your testbench file?

    Thank you for your attention!
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    7 years ago

    Hi,

    Yes, It should be "clk_clk".

    Refer attached testbench file & run for more time like "run 50 ms".

    Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

    Best Regards

    Vikas Jathar

    (This message was posted on behalf of Intel Corporation)
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    7 years ago

    Nothing helps me :c

    Maybe smth broken in Native link connetion. But when I intentionally made mistake in .vt file, Modelsim reported me about it so it sees and updates it during RTL simulation.

    You seemed to simulate this project without Quartus, how?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    7 years ago

    Hi,

    I created own simple design file relative to the .vt file, refer the attached files & try yourself with fresh new project in Quartus tool.

    Let me know if this has helped resolve the issue you are facing or if you need any further assistance.

    Best Regards

    Vikas Jathar

    (This message was posted on behalf of Intel Corporation)