System Verilog Questions and Tricks

System Verilog Questions and Tricks - I

Queues

Finite Queues

What happens when you read from empty queue?

Well, that depends on the what type of que it is. As in, lets say if the que is of the pre defined data type like int, real and others.. the return value will be '0'.

If the que is of a class or any dynamic objects, then the return value will be null.

a inta[$];
int fintq[$:2];

In the above code, when you pop empty que of class a, then the return value will be NULL pointer When you pop from the Int que, the result will be '0'

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Verdi Uses - I

COVERAGE While going through some of the blog posts, i found that the Verdi supports even coverage right out of the box, but from the 2014 Version. Well till now, we relied on the URG reports and the DVE to review the coverage and apply waivers and create exclusion files. Looks verdi supports all the features.. I did not get any hands on the features of this option, soon i will find some time to play around with this option of coverage in Verdi. How to launch the verdi with coverage. $> verdi -cov -covdir <PATH_TO_TB>.simv.vdb -covdir <PATH_TO_TEST1>.simv.vdb -covdir <PATH_TO_TEST2>.simv.vdb... You can pass multiple covdirs, where in all the results will be merged. References: SYNOPSYS SITE Think Verification

Sequence Layering in UVM

What is Sequence Layering? Sequence layering is refered to as running sequences inside sequences. So whats the big deal. There are virtual sequences we will use to run multiple sequences. A generic example of sequence layering. you have two sequences Interrupt sequence register read write sequence. Generally when you have interrupt, we generally enter into interrupt service routine, which can be implemented as an interrupt sequence. So when you run an interrupt sequence, you might end up running register read /write sequence like polling or clearing interrupts. Well thats easy, just run one sequence in another. class top_seq extends uvm_sequence#(txn_item); //Two sequencers say.. sub sequences. sub_seq1 seq1; sub_seq2 seq2; ... task body(); seq1.start(some_seqr); seq2.start(some_seqr2); endtask endclass Killing sequences: That was great you are running nested sequences. But how to kill them when needed. UVM provides method cal

SystemVerilog: Mailboxes and Queues

Mailboxes and queues are couple of basic data constructs of system verilog language. Lets get to the definition of them: Queue: A Queue in system verilog function as the name suggests. But with a twist. Queue in system verilog is a list of similar elements. Queue is built on top of an array. Delcaration of a queue. < TYPE > < que_name >[ $ ]; Default Behaviour: The default size of the queue in system verilog is " Infinite ". The above declaration will create a que of infinite length. You can add elements to the que until your simulator crashes :) What if you want to create a queue of finite length. Just look at the declaration below: < TYPE > < que_name >[ $ :< LIMIT >]; The above declaration will create a queue of size " LIMIT+1 " Initializing queue with elements Accessing elements of a queue Methods in queue Inserting elements into queue Reoving elements from queue http://www.project-veripage.com/queue_1.ph

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