Flow control with virtual sequence

UVM
, ,
1

Hi all!
i’m trying to make a virtual sequence with a little bit more complex flow control, then described in UVM cookbook (maybe, there are examples there like the one i need, but i could’n find it=\ ).

class enchancer_virtual_sequence extends uvm_sequence#( uvm_sequence_item );

  v_data_sequencer	#(...)  v_data_seqr;

  enchancer_coefs_sequencer 	enchancer_coefs_seqr;
	
  v_data_sequence 					v_data_seq;
  enchancer_coefs_sequence 	enchancer_coefs_seq;
	
	
  function new( string name = "" );
     super.new( name );
  endfunction: new

task body();
fork: f_block
begin
v_data_seq = v_data_sequence::type_id::create( .name( "v_data_seq" ) );
v_data_seq.start( .sequencer( v_data_seqr ), .parent_sequence( this ) );
disable f_block;
end
			
begin
forever
begin
enchancer_coefs_seq = enchancer_coefs_sequence::type_id::create( .name( "enchancer_coefs_seq" ) );
enchancer_coefs_seq.start( .sequencer( enchancer_coefs_seqr ), .parent_sequence( this ) );

end
end
join

endtask: body
   
   `uvm_object_utils( enchancer_virtual_sequence )

endclass: enchancer_virtual_sequence

i have two flows here: one with video data, and another with coefficients.
video ata sequene looks like this

class v_data_sequence extends uvm_sequence#( v_data_transaction	#(...));

  function new( string name = "" );
    super.new( name );
  endfunction: new
  
task body();
  v_data_transaction	#(...) v_data_tx;
int line_num = 0;
int elem_n = 0;

for (int line_num = 0; line_num < 1024; line_num++)
begin
for (int elem_n = 0; elem_n < 20+4+4; elem_n++)
begin
v_data_tx = v_data_transaction	#(...)::type_id::create( .name( "v_data_tx" ));
start_item( v_data_tx );
assert( v_data_tx.randomize() );

if ((elem_n >= 4) && (elem_n <= 23))
begin
v_data_tx.x_active = 1;
end
else
begin
v_data_tx.x_active = 0;
End
finish_item( v_data_tx );
end
end
endtask: body

  `uvm_object_utils( v_data_sequence )

endclass: v_data_sequence

i want to send coefficients onle when x_active (signal in video data flow) is low. Yet i don’t know, what is the proper way to synchronize my coefficient flow with this event.

here’s video data seqence item:

class v_data_transaction #(...) extends uvm_sequence_item;
  
 rand bit [N_COMP-1:0][V_DATA_WIDTH-1:0] v_data;
 rand bit [Y_WIDTH-1:0] y;
 rand bit[X_WIDTH-1:0] x;
 bit x_active;
...

how should i synchronize my data lows?
thank you for reading

2

In reply to trogers:

Hi trogers,

I think if there is virtual interface handle in the env config, the signal information can be got in the virtual sequence through its sequencer.

Best regards,
Yao He

3

In reply to yaohe:

Hi yaohe,

thank you for your reply.
I’m not sure that i understand it. You want to say, that i need to track signal “x_active” through virtual interface from my virtual sequence? If that’s correct, could you please give an example?

4

Ok, i’ve found out how to synchronyze my sequences. i’ve decided to write tasks in agent’s configuration objects, like this:

class v_data_agent_config #(
parameter V_DATA_WIDTH = 10,
parameter N_COMP       = 1,
parameter Y_WIDTH      = 10,
parameter X_WIDTH      = 10
) extends uvm_object;
  `uvm_object_param_utils( v_data_agent_config #(
.V_DATA_WIDTH(V_DATA_WIDTH),
.N_COMP(N_COMP),
.Y_WIDTH(Y_WIDTH),
.X_WIDTH(X_WIDTH)
)
)

  uvm_active_passive_enum active = UVM_ACTIVE;// if active, has sequencer and driver,
	//otherwise has only monitor
  bit has_v_data_fc_sub = 1; // switch to instantiate a functional coverage subscriber
	
  virtual v_data_if #(
.V_DATA_WIDTH	(V_DATA_WIDTH),
.N_COMP	(N_COMP),
.Y_WIDTH		(Y_WIDTH),
.X_WIDTH		(X_WIDTH)
) v_data_bus;
	
	
  function new( string name = "" );
    super.new( name );
  endfunction: new
	
	extern task wait_for_unactive_part;
	
endclass: v_data_agent_config

task v_data_agent_config::wait_for_unactive_part;
	@(negedge v_data_bus.x_active);
endtask: wait_for_unactive_part

class avalon_mm_agent_config #(
parameter ADDR_WIDTH = 10,
parameter DATA_WIDTH = 10
) extends uvm_object;
	`uvm_object_param_utils( avalon_mm_agent_config #(
.DATA_WIDTH(DATA_WIDTH),
.ADDR_WIDTH(ADDR_WIDTH)
)
)

	uvm_active_passive_enum active = UVM_ACTIVE;// if active, has sequencer and driver,
	//otherwise has only monitor
	bit has_avalon_mm_fc_sub = 1; // switch to instantiate a functional coverage subscriber
	
	virtual avalon_mm_if #(
.DATA_WIDTH(DATA_WIDTH),
.ADDR_WIDTH(ADDR_WIDTH)
) avalon_mm_bus;

	function new( string name = "" );
		super.new( name );
	endfunction: new
	
	task wait_for_readdata (bit [DATA_WIDTH-1:0] readdata);
		@(posedge avalon_mm_bus.readdatavalid);
		readdata = avalon_mm_bus.readdata;
	endtask

	task wait_clock (int i);
		repeat (i) @(posedge this.avalon_mm_bus.clk);
	endtask
	
endclass: avalon_mm_agent_config

i have these configuration objects in uvm database, so i “::get” them in my sequences and use task to synchronize.
BUT i get an error at elaboration time:

" Virtual interface resolution cannot find a matching instance of interface 'avalon_mm_if '."

Elaboration goes well for ‘v_data_if’, but fails for ‘avalon_mm_if’.

i commented tasks in avalon_mm_agent_config and looked local variables it that object. This interface does exist (it’s not null). And, actually, my driver sends data through it.

Here Virtual interface resolution cannot find a matching instance of interface | Verification Academy i’ve found posts, describing a problem, which looks just like mine, but didn’t find an explanation, because true matching interface IS found (otherwise avalon_mm_bus would be null, right?). Why does this happen? Is it Questa’s bug?