UVM

Advantages	DisAdvantages
1. Modularity and Reusability	1. Steep Learning Curve
2. Separating Tests from Testbenches	2. Still in development
3. Simulator independent	3. Too many Functions and Tasks
4. Sequence based Stimulus generation	4. Overkill for small agents
5. Configuration mechanisms	5. Bottleneck - lot of code to create TB
6. Factory mechanisms
7. Plug and Play
8. Bidirectional
9. Phasing mechanisms

Copy	Clone	Create
The copy makes this object a copy of the specified object.	The clone method creates and returns an exact copy of this object.	The create method allocates a new object of the same type as this object and returns it via a base uvm_object handle.
The do_copy method is the user-definable hook called by the copy method.	The default implementation calls create followed by copy. As clone is virtual, derived classes may override this implementation if desired.	Pure virtual class. Hence, every class deriving from uvm_object, directly or indirectly, must implement the create method.

uvm_object

SEEDING	IDENTIFICATION	CREATION	PRINTING	RECORDING
use_uvm_seeding	set_name	create	print	record
reseed	get_name	clone	sprint	do_record
	get_full_name		do_print
	get_inst_id		convert2string
	get_inst_count
	get_type
	get_object_type
	get_type_name

COPYING	COMPARING	PACKING	UNPACKING	CONFIGURATION
copy	compare	pack	unpack	set_int_local
do_copy	do_compare	pack_bytes	unpack_bytes	set_string_local
		pack_ints	unpack_ints	set_object_local
		do_pack	do_unpack

Agent Mode

The int configuration parameter is_active is used to identify whether this agent should be acting in active or passive mode. This parameter can be set by doing:

uvm_config_int::set(this, "<relative_path_to_agent>, "is_active", UVM_ACTIVE);

get_is_active() returns UVM_ACTIVE if the agent is acting as an active agent and UVM_PASSIVE if it is acting as a passive agent.

Starting a test

A particular test case can be selected and execute on two methods,

by specifying the test name as an argument to run_test();
- example: run_test("mem_model_test");
by providing the UVM_TESTNAME command line argument
- example: <SIMULATION_COMMANDS> +UVM_TESTNAME=mem_model_test

run_test( ) within tb_top as shown above, is a global task which is responsible for getting a reference to the uvm_root class instance from UVM core services.
There is another run_test( ) method within uvm_root to
- phases all components through all registered phases.
- initialize factory settings
- report servers
- do basic level checks

Pre and post body in a Sequence

The *_body() callbacks are designed to be skipped for child sequences, while *_start() callbacks are executed for all sequences.

virtual task start (
  uvm_sequencer_base sequencer, // Pointer to sequencer
  uvm_sequence_base parent_sequencer = null, // parent sequencer
  integer this_priority = 100, // Priority on the sequencer
  bit call_pre_post = 1 // pre_body and post_body called
);

Seq arbitration

seqr.set_arbitration(); Specifies the arbitration mode for the sequencer.

function void set_arbitration(
UVM_SEQ_ARB_TYPE val
)

Arbitration	Order
UVM_SEQ_ARB_FIFO (default)	Requests are granted in FIFO order
UVM_SEQ_ARB_WEIGHTED	Requests are granted randomly by weight
UVM_SEQ_ARB_RANDOM	Requests are granted randomly
UVM_SEQ_ARB_STRICT_FIFO	Requests at highest priority granted in FIFO order
UVM_SEQ_ARB_STRICT_RANDOM	Requests at highest priority granted in randomly
UVM_SEQ_ARB_USER	Arbitration is delegated to the user-defined function, user_priority_arbitration. That function will specify the next sequence to grant.

Exclusive access for the seqr

different from m and p seqr so need help might be lock

m_sequencer	p_sequencer
generic uvm_sequencer pointer	typed-specific sequencer pointer
initialized when the sequence is started	you would need to typecast the m_sequencer to the physical sequencer
a handle of type uvm_sequencer_base which is available by default in a sequence	created by registering the sequence to the sequencer using macros.It will not exist if we have not registered the sequence with macros

Default sequencer

m_sequencer, available in any sequence, is the default sequencer
A specific sequencer can be set using
- uvm_sequence_item::set_sequencer() in sequence_item
- create_item( ..., .l_sequencer(seqr)) in sequence

Sequencer - Driver Interactions

get_next_item and get will retrieve the next available item from a sequence. The call will block until an item is available.
try_next_item will try to retrieve if available, if not returns immediatly with request set to null object.
peek will retrieve the present availabe item from a sequence. The call will block until an item is available.
- Once a request item has been retrieved and is in the sequencer FIFO, subsequent calls to peek will return the same item.
- The item will stay in the FIFO until either get or item_done is called.

The following steps occur on these calls:

No.	Retrieves the next available item from a sequence
1	Seq Arbitration
2	return from `wait_for_grant` in sequence
3	Randomizaion
4	Indicate `item_done` to the sequencer (only in `get`)
5	return with a reference to the item

item_done will :-

Indicates that the request is completed to the sequencer.
- Any uvm_sequence_base::wait_for_item_done calls made by a sequence for this item will return.
The current item is removed from the sequencer FIFO.
If a response item is provided, then it will be sent back to the requesting sequence.
- The response item must have its sequence ID and transaction ID set correctly, using the uvm_sequence_item::set_id_info

Factory

Using the factory involves three basic operations

Registering objects and components types with the factory
Designing components to use the factory to create objects or components
Configuring the factory with type and instance overrides, both within and outside components

new	create
SV	Factory - UVM
class constructor which is used to create an instance of a class	factory method that is used to create the instances of uvm components & objects with the help of class constructor
No Factory registeration	Factory can only create the instances of the class which are registered with it
No Factory Overriding	Can be overrided

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