In reply to SriGanesh D:
In general, you want all of the testbench stimulus generation and response (i.e. sequences) to be configured/started during the run_phase() of your test. This is desired to allow the user to control the exact relationship between these sequences.
There are several reasons using a default_sequence doesn’t follow this:
- Setting a default_sequence is done outside of the run_phase(). Additionally, changing the default_sequence requires changes outside of the run_phase().
- There is no mechanism to control when the default_sequence starts, other than at the beginning of a specific phase.
- You can’t run more than one sequence
- You can’t easily run additional sequences on the same sequencer
- Debugging a default_sequence can be difficult since the user may not be aware that the default_sequence exists.
- The default_sequence can’t be randomized() or otherwise configured
It’s simple enough to create()/randomize()/start() a single sequence at the beginning of the run_phase() instead of setting a default_sequence.