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System Verilog Assertions

Manasy M
Manasy M over 6 years ago

Hi all,

I have the following scenario for writing assertion.

Signal  'A' rises two cycles after 'B' falling. The high period of 'A' is, 70 + (var_value) clock cycles.

'var_value' is a variable

I wrote two assertions to check this scenario;

1. property A_RISE;
    @(posedge clk) 
    $fell(B) |-> ##2 $rose(A);                                                //to check the dependency of A w.r.t B
    endproperty

    ASSERT_A_RISE : assert property(A_RISE);

2. property A_HIGH_PERIOD;
    @(posedge clk)
     $rose(A) |-> A[*70] ##1 A[*var_value] ##1 !A;           //to check the high period of A;  ERROR: var_value must be a constant
    endproperty

    ASSERT_A_HIGH_PERIOD : assert property(A_HIGH_PERIOD);

Is there any better way to check both dependency and high period together?

How can we use variable cycle delays or sequence repetitions in assertion properties??

I have started to practice system verilog assertions recently only; Please provide me some guidelines to proceed with this.

Thanks

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  • TAM1
    TAM1 over 6 years ago

    There is an article showing the best way to do this on the Cadence web site:

    Article (11628272) Title: The cycle count in an SVA or PSL assertion must be a compile-time constant
    URL: https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od0000000nTuCEAU

    It uses a local variable to hold the number of cycles that A has been high so far.

    property p1;
      int count;
      @(posedge clk)($rose(A),count=0) |-> (A && (count<(70+var_value))),count=count+1)[*]
                                           ##1 (count==(70+var_value) && !A;

    endproperty : p1
    assert property (p1);

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  • StephenH
    StephenH over 6 years ago in reply to TAM1

    Manasy M said:

    Is there any better way to check both dependency and high period together?

    Speaking from personal experience, I would advocate keeping two simple properties, rather than making a single complex property; it's easier to debug failures.

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  • StephenH
    StephenH over 6 years ago in reply to TAM1

    Manasy M said:

    Is there any better way to check both dependency and high period together?

    Speaking from personal experience, I would advocate keeping two simple properties, rather than making a single complex property; it's easier to debug failures.

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  • Manasy M
    Manasy M over 6 years ago in reply to StephenH

    Thank you for the advice. I will proceed in this way.

    How does the assertions affect simulation time?? Will multi thread assertions slow down the simulation time? If it does, what is the best way of writing assertions, which will avoid this problem?

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