How to workaround "System function calls are not yet implemented in constraints"?

UVM
1

Hi,

In the following code, I need to send a randc data for each resp[i], but the randomize() is not supported in the constraint, how can I implement this? Please advise! Thanks!


class rand_resp extends uvm_component;
   randc bit[5:0] data;
end class : rand_resp

class abc_seqeunce extends base_sequence;
rand_resp  m_rand_resp;
endclass : abc_sequence

virtual task body() ;
 `uvm_rand_send_with(item,
	{
	   foreach(resp[i]) {
				        
		m_rand_resp.randomize();
		resp[i] == m_rand_resp.data;
					
	   }
        )
2

Your code isn’t very clear with respect to what you are trying to accomplish. I don’t see where resp is an array, so I’m not sure why you are using a foreach() construct.

Also, you shouldn’t use the uvm_rand_send_with macro (or any other uvm_send* macro). Try writing out your sequence using the appropriate APIs and it will probably be easier for you to understand what your issue is.

Note that ‘randc’ is only valid for a single class instance. The `uvm_send_* macros will create() a new object every time, which is why their usage isn’t recommended.

3

In reply to cgales:

Thanks Cgales for the reply. What would be the equivalent code to the macro of `uvm_rand_send_with ? the code was trying to send out a request of a burst, so there is an array there …

4

In reply to nickbayshore:

Can you post the complete code for your sequence?

Read the chapter from the UVM Cookbook on Sequences to see how you should generate and send sequence items.

5

In reply to cgales:

Thanks Cgales. I have replaced the macro with normal sequence code (e.g. start_item() … finish_item()), and it’s working now …

You mentioned ‘randc’ is only valid for a single class instance. If I have the following class gets instantiated by different sequence, the randc value won’t be unique anymore for a single simulation run? Thanks!


 class abc extends uvm_object;
   randc bit[5:0] data;

`uvm_object_utils(abc)

 function new(string name = "abc");
    super.new(name);
  endfunction : new

endclass : abc
6

In reply to nickbayshore:

The ‘randc’ qualifier is only valid for a specific instance of a class. If you create a second instance, ‘randc’ is independent for that second instance and has no effect on the first instance.

7

In reply to cgales:

Thanks Cgales. That makes sense. Do you have idea how to make “data” generated in two different sequences are unique? using a common list and exclude from that list every time? Looks like using randc can only guarantee the data generated in the current sequence are unique … Thanks!

8

In reply to nickbayshore:

If you want to create sequences with unique data, then you should use a virtual sequence that creates the data and then starts sub-sequences ensuring that each sequence is initialized with the unique data.

9

In reply to cgales:

Thanks Cgales. Could you point me to some examples? Thanks!

10

In reply to nickbayshore:

I’m reading the “ResourcesAccessforSequence” in Verification Academy to see if I can figure out … Hope that’s the right one to read … Thanks!