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calling run_test() at no-zero time

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I am working on ovm to uvm migration.

In my ovm environment run_test is called after 2us in the top module initial block.

But when i give the same delay in uvm environment it is giving an error.

"No non-zero delays are allowed before run_test()"

I could find that there is a fatal error message in uvm library as follows:-


task uvm_root::run_phase (uvm_phase phase);

if($time > 0)

`uvm_fatal("RUNPHSTIME", {"The run phase must start at time 0, current time is ",

$sformatf("%0t", $realtime), ". No non-zero delays are allowed before ",

"run_test(), and pre-run user defined phases may not consume ",

"simulation time before the start of the run phase."})



I am using run_phase() in testcase.

And I need to have some delays before I call run_test.

Please suggest some solution. Thanks in advance.


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> And I need to have some delays before I call run_test.

Why? What happens before that point in time?? And why isn't it driven by UVM??

If you implement your tests in main_phase(), you are free to insert any delay before it begins. But the UVM testbench hierarchy should exists (and run) from the beginning of time.

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uvm doesnt allow time being spend before run_test(). anything between run_test() and run_phase() basically builds the static infrastructure/topology - then real wall clock time is spend with the created instances. so please describe your use model and i'm this also fits into the uvm infrastructure

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Maybe it is an env ported from OVM? We have seen several users doing this in OVM - simply b'cos OVM allowed only one task - run(). Many simple designs need simple reset toggling before starting transactions, hence this was convenient (than doing a virtual sequence etc.).

Maybe same reason with jithinraj1989 too?

BTW - the fix above rationale in UVM would be to move the reset to reset_phase.


Ajeetha, CVC


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