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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

Virtual sequences and sequencers in UVM are just virtual containers of multiple sequences and sequencers. Using virtual sequencers and sequences can be done in these three ways: Using only virtual Sequence and handles of sequencers inside the virtual sequence. Using Virtual sequencer to hold the sequencers Same as step 2, by using uvm_declare_p_sequencer. Virtual Sequencer does not create any sequencer objects, rather it points to other physical sequencers in different agents.  Virtual Sequencer extends from uvm_sequencer. Virtual sequence will create its sequences and start them. Running sequences can be controlled by user in the body() task. virtual sequence extends from uvm_sequence. METHOD-1: In this method, we will have one base virtual sequence which will hold the handles to different sequencers. Here we dont use any virtual sequencer. We just use the nested seqeunces with handles ot sequencers inside sequence itself. //This is the base virtual sequen